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Food Sciences and Nutrition 112
Principals of Human Nutrition
Food and Nutrition: An Introduction
From birth to death food is a dominant factor in our life. Besides providing
the energy for breathing at night and full activity during daytime, food builds,
maintains, and regulates muscles and bones, nerves and brain, eyes, hair, and all
our physical being. Food is also used as a link in our friendship, and as a symbol
of our religious life. Through the ages, people have learned that some foods are
more nourishing than others. The science of nutrition, on the other hand, was
grown only after the development of the sciences of chemistry and physiology and
had its beginning in the late eighteen century. Thereafter, since 1900, the
functions of the nutrients in the body, the nutritive values of foods, the body
requirements for nutrients, and the role of nutrition in health and disease were
studied. It should be emphasized that much still remains to be learned.
1
Commonly used terms in nutrition
Nutrition : The sum of processes involved in taking in food and using them for
growth, development, and the maintenance of health. It includes eating the correct
kind and amount of food, digestion, and absorption of the nutrients for the
maintenance of body tissue, production of energy, and elimination of wastes.
Nutritional science: The body of knowledge developed through controlled
research that relates to the process involved in nutrition. It includes managing
food requirements of humans for maintenance, growth, activity, reproduction, and
lactation.
Nutrients: Any chemical substance found in food that is used to promote body
functions. They are divided into six basic groups: carbohydrates, fats, proteins,
vitamins, minerals, and water.
Nutrient requirement: A Specific amount of a specific nutrient needed by the
body at a certain age.
Essential Nutrients: Nutrients that are necessary for life and can’t be synthesized
by the body and therefore, must be included in the diet.
Food: Any substance, usually of plant or animal origin, when eaten, digested, and
absorbed provides one or more of the nutrients.
Diet: Includes the kinds and amounts of food and drink consumed each day. It
includes both the normal and the therapeutic diet.
2
Balanced Diet: A diet that provides all the essential nutrients in appropriate
amounts.
Nutritional Status: The physical condition of the individuals that can be
determined by their diet.
Nutritional Assessment: The measurement of nutritional status based on
anthropometric and biochemical data and dietary history.
Health: The state of complete physical, mental, and social well-being and not
merely the absence of disease.
Malnutrition: Any disorder concerning nutrition. It may result from an
unbalanced, insufficient, or excessive diet. It includes:
Overnutrition: The condition that results from excessive caloric intake
and/or one or more nutrients.
Undernutrition: The condition that results from an insufficient caloric
intake and/or one or more nutrient.
Recommended Dietary Allowance (RDA): The average daily nutrient intake
level that is sufficient to meet the nutrient requirements of nearly all (97-98%)
healthy individuals in a particular life stage and gender group.
Energy: The capacity to do work. Food provides the body with energy or fuel it
needs to stay alive, move, and grow. The chemical energy found in food and used
by the body is measured in kilocalorie (Kcal) or calorie (cal).
Energy Yielding Nutrients: Nutrients that the body can use for energy
production (carbohydrate, fat, and protein).
3
Calories: Units of energy. It is the amount of heat required to raise the
temperature of a kilogram of water one-degree Celsius.
Metabolism: The sum of all chemical changes that take place in the body by
which it maintains itself and produces energy for its functioning. Metabolism is of
two types:
Anabolism: The synthesis of complex molecules from simpler ones. The
reaction is energy dependent (e.g: growth).
Catabolism: The break down of complex molecules to simpler ones,
which leads to the release of energy (e.g: starvation, illness).
4
Tools for Choosing a Healthy Diet
Understanding Food Labels
Ingredient List: The ingredient list includes all of the substances added
when preparing a food, including food additives, colors, and flavoring. The
ingredients are listed in order of their prominence by weight.
Nutrition Facts: Lists the serving size of the food followed by the total
calories, calories from fat, total fat, saturated fat, cholesterol, sodium, total
carbohydrate, dietary fiber, sugars, and protein per serving of the food.
Illustration:
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The Food Guide pyramid: In June 2011, MyPlate replaced MyPyramid.
A website — ChooseMyPlate.gov — which contains resources and tools
for more specific information about what and how much to eat.
On this website, consumers will find specific recommendations for each
USDA Food Group, based on the 2010 Dietary Guidelines for Americans
(DGA), including proportions based on research that relate to individual
calorie and nutrient needs.
The new MyPlate icon is a plate split into four sections, each representing a
different type of food (protein, whole grains, fruits and vegetables). The sections
vary in size depending on the recommended portion of each food a person should
eat. A circle shape next to the plate represents dairy products, especially milk.
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Viewing the icon online allows consumers to click on each section of the plate
for more information.
Functions of Foods
Food is any material, solid or liquid, which after ingestion, digestion and
absorption is used to build and maintain body tissues, regulate body processes and
supply energy.
Foods provide:
Water (environment in which cells live)
Fuel for energy (so that cells can do their work)
Building blocks (nutrients that cells use to build and repair themselves)
Metabolic regulators (nutrients that cells use to coordinate life’s processes)
The six essential nutrients and their functions
Carbohydrates Provide energy and heat
Fats Provide energy and heat
Proteins Build and repair body tissue
Provide energy and heat
Vitamins Regulate body functions
Minerals Regulate body functions
Water Regulate body functions
7
1. Energy and Heat:
Dietary carbohydrates: starches and sugars are body’s primary source of fuel for
heat and energy. They also maintain the body store of quick energy as glycogen.
Each gram of carbohydrates yields 4 calories. Carbohydrates should provide 50-
66% of the total calories.
Dietary fats: provide the body with heat and energy. It is the most concentrated
form of energy yielding 9 calories/gm. Fats should provide no more than 25-30%
of the total calories, with at least 50% of this amount being unsaturated fats from
plant sources.
Dietary proteins: the body may use dietary or tissue proteins to obtain energy
when the supply of fuel from carbohydrates and fats is not enough. The fuel factor
for protein is 4 calories. Protein should provide 15-20% of the total calories.
2. Tissue building:
Proteins: primary function is tissue building. Dietary protein provides amino
acids, the building units necessary for constructing and repairing body tissues.
This is a constant process that ensures growth and maintenance of a strong body
structure as well as vital substances for the tissue function.
Minerals: such as calcium and phosphorus, which build and maintain bone tissue.
Iron is part of Hemoglobin.
Vitamins: Vitamin C is involved in developing the cementing intercellular ground
substance. The substance helps build strong tissue and prevents tissue bleeding.
8
Fat: Fatty acids help build the central fat substance of cell walls, which promotes
transport of fat-soluble material across the cell wall.
3. Regulation and control:
All the chemical processes in the body needed for providing energy and building
tissue are regulated and controlled to maintain a smooth, balanced operation.
Nutrients that help regulate body processes are:
Vitamins: many vitamins function as coenzyme factors. They are components of
cell enzymes that control chemical reactions in cell metabolism (for example most
of the b-complex vitamins). Almost every action in the body requires the
assistance of vitamins.
Minerals: many minerals serve as coenzyme factors such as cobalt, which is a
central constituent of B12 vitamin (antipernicious anemia vitamin).
Water and fibers: function as regulatory agents. Water is the fundamental agent
for life, providing the essential case for all the metabolic processes. Fibers help in
regulating the passage of food materials through the gastrointestinal tract and
influence the absorption of various nutrients.
Balanced Diet:
1. Adequate (provides enough of each essential nutrient, fiber and energy).
2. Balanced (does not over emphasize one food type or nutrient at the expense of
another).
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3. Caloric controlled (provides the desired energy for the body).
4. Moderate (does not provide excess intakes of fat, salt, sugar).
5. Variety (different foods to provide different nutrients).
6. Energy intake balanced with energy expenditure (calories in = calories out).
Digestion, absorption and metabolism
Digestion:
The process whereby food is broken down into smaller parts (absorbable
units), chemically changed, and moved through the gastrointestinal (GI)
system. The process of digestion begins in the mouth.
Digestive system: All body structures that participate in digestion.
Digestion is of two parts:
1. Mechanical (teeth: crush large pieces of food into smaller ones; peristalsis: wavelike muscular contractions of the GI tract that push its contents along)
2. Chemical (hydrolysis: addition of water to break a molecule into smaller pieces; digestive enzymes: proteins that act on food substances, causing them to break down into simpler compounds)
Digestion in the mouth:
Chewing food and mixing with saliva (salivary amylase), initiates the
digestion of carbohydrates.
Salivary amylase acts on starch (very little is changed)
Digestion in the stomach:
Gravity and peristalsis transfer food down the tract.
Stomach mixes food with gastric juices.
Gastric juices:
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Pepsin → Protein
Rennin → Proteins in milk
Gastric Lipase → Emulsify fat
Gastric juices contain HCL
Functions of HCL:
- Break down food to make them easily attacked by the enzymes.
- Provides the acid medium necessary for the action of pepsin.
- Increases the solubility of calcium and iron salts to enhance their
absorption.
- Destroys bacteria present in food.
Mucus, a thick, slippery, white substance that coats the stomach’s cells, is
secreted by the goblet cells of the stomach wall to protect themselves from
gastric juice.
Peristalsis moves the chyme towards pylorus, which is then released
gradually into the duodenum (first part of the small intestines).
Digestion in the small intestine:
Chyme in the duodenum, specifically fat, stimulates the secretion of a
hormone cholecystokinin (CCK), which causes the gallbladder to contract to
release bile into the duodenum.
Bile is produced in the liver and stored in the gallbladder.
Bile has the function of fat emulsification (brings fat into suspension so
enzymes can act upon them).
Chyme stimulates the pancreas to secrete pancreatic juices into small
intestine.
The pancreatic juice contains enzymes that act on all three energy nutrients.
Pancreatic juices:
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- Pancreatic amylase (split starch to maltose)
- Trypsin (break down proteins to smaller molecule)
- Lipase (break down fats to fatty acids and glycerol)
- Sodium bicarbonate, which is basic (a neutralizing agent)
Intestinal juices (cells of the intestinal wall): lactase, maltase, sucrase,
peptidases.
Most of the other nutrients-vitamins, minerals, and water-need no such
disassembly; some are altered slightly, but most are absorbed as they are.
Absorption:
The passage of nutrients into the body fluids and tissues.
Nutrients must be in simplest form
Carbohydrates → glucose, galactose, fructose
Proteins → amino acids
Fat → fatty acids and glycerol
Most absorption of nutrients occurs in the small intestine through villi,
fingerlike projections from the folds of the small intestine, which are
composed of the microvilli, hairlike projections on each cell of every villus
that trap nutrient particles and transport them into cells.
Large intestine absorbs water and salts and collects bulk.
In healthy individuals more than 90% of the nutrients are absorbed.
Metabolism:
Complex process that changes the nutrients in order to produce energy,
which form tissues, and maintain control and regulation over body
functions.
Nutrients undergo oxidation
Carbohydrates, fats Co2 + H2 O
Proteins Co2 + H2O + N
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Anabolism: the formation of complex molecules from simpler ones
Catabolism: the breakdown of molecules to simpler ones like in surgery
burns and during period of high fever.
Metabolism is regulated by the thyroid gland.
Carbohydrates
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Definition: Carbohydrates are organic compounds that consist of carbon,
hydrogen, and oxygen arranged as monosaccharides or multiples of
monosaccharides. All carbohydrates except dietary fibers provide 4 kcal/g.
Sugars and Starches
Nature: Carbohydrates are formed from green plants through photosynthesis by
which sugar is formed from Co2 and H2O by the aid of sunlight and chlorophyll.
Functions:
1. Provide energy for body functions and heat to maintain body temperature.
2. Spare proteins for energy.
3. Aid in the synthesis of non-essential amino acids.
4. Required for the complete oxidation of fat.
5. Lactose increases the absorption of calcium and phosphorus and favors the
growth of certain intestinal bacteria that synthesize some of the B-complex
vitamins.
6. Gives flavor and texture to the diet.
Daily Requirements:
The daily diet should not contain less than 100 gms of carbohydrate.
About 55 to 60% of the total caloric intake should be provided through
carbohydrates.
Sources:
Cereal grains (rice, wheat, corn, oats, rye).
Green leafy vegetables are high in fibers.
Roots, tubers and seeds contain more complex carbohydrates (corn, potatoes,
dried peas, beans).
Fruits contain sugars and fibers.
Sweets provide different types of sugars.
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Animal sources include lactose in milk and glycogen in meats (limited extent).
Classification:
Class Examples
Monosaccharides (single sugars) Glucose
Fructose
Galactose
Disaccharides (double sugars) Sucrose
Maltose
Lactose
Polysaccharides (complex carbohydrates) Starches
Glycogen
Dextrin
Dietary Fibers
Monosaccharides (simple carbohydrates):
Simplest form of carbohydrates.
Requires no digestion and are absorbed directly from the small intestine.
Disaccharides (simple carbohydrates):
Lactose composed of glucose and galactose.
Principal carbohydrate of milk
Maltose composed of two glucose molecules.
Whenever starch breaks down
Fermentation process yields that yields alcohol
Minor constituent of a few foods
Sucrose composed of glucose and fructose.
Natural sweetness of fruits, vegetables, and grains
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Refined to make table sugar
These carbohydrates and all the other energy nutrients are put together
and taken apart by a similar chemical reaction: condensation and
hydrolysis.
Must be changed to simple sugars before they can be absorbed.
Maltose is an intermediate product in the digestion of starch inside the
body.
Polysaccharides (complex carbohydrates):
Starch is the plant storage form of glucose (long, branched or un-
branched chains of hundreds or thousands of glucose molecules).
Derived from plants
Richest in grains; wheat or rice, in tubers such as potatoes, and in
legumes such as peas and beans.
Glycogen is the form in which carbohydrates are stored in the body
(liver and muscles).
Dextrin is a digestible polysaccharide that is an intermediate product
from the hydrolysis of starch.
Fibers provide structures in stems, trunks, roots, leaves, and skins of
plants, which are compose of a variety of monosaccharides and other
carbohydrate derivatives.
Digestion, Absorption and Metabolism:
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The goal of digestion is to reduce the complex and double sugars to simple sugars.
Digestion
Mouth: cooked starch Small Poly, Maltose
Stomach: No action. Acid inactivates salivary enzyme.
Small intestine: Starch Maltose
Sucrose Glucose, Fructose
Maltose 2 Glucose
Lactose Glucose, Galactose
Absorption
Small Intestine: Glucose absorbed. Fructose and galactose can eventually
become glucose after being processed in the liver.
MetabolismGlucose Co2 + H2O + energyChanged to glycogen and stored in liver and muscles.Changed to fat and stored in fatty tissues.
Dietary fiber
- Divided into two groups
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Salivary amylase
Sucrase
Maltase
Amylase
Lactase
Oxidation
- Fibers that are not soluble in water (structural fibers): whole wheat and rye,
wheat bran, seeds, nuts.
- Water-soluble (nonstructural): apples, grapes, plums. Citrus fruits, oatmeal,
oat bran, beans.
Health benefits of fibers:
Increase sense of fullness
Reduces energy consumption, which helps in weight control.
Prevent constipation.
Increase fecal weight (promotes bowel movements).
Help prevent bacterial infection.
Reduces colon cancer.
Improve the regulation of blood sugar (delaying glucose absorption).
Lower the blood cholesterol and triglycerides (benefits heart health).
Glucose in the body:
Every body cell depends on glucose for its fuel to some extent, and ordinarily, the
cells of the brain and the rest of the nervous depend primarily on glucose for their
energy.
Homeostasis: the body must maintain blood glucose within limits that permit
the cells to nourish them-selves. If the glucose falls below normal, the person
may become dizzy and weak; if it rises above normal, the person may become
fatigued.
Regulating hormones:
o Primarily by two hormones (from cells in the pancreas): insulin, which
moves glucose from the blood into the cells, and glucagon, which
brings glucose out of the storage when necessary.
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o Epinephrine: another hormone of the adrenal gland that modulates the
stress response. Like glucagon, it works to release glucose from the liver
glycogen to the blood.
Proteins
Definition:
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- Proteins are large, complex, nitrogen containing compounds.
- In addition to the carbon, hydrogen, and oxygen that carbohydrates and lipids
contain, proteins also contain nitrogen.
- Each gram of nitrogen = 6.25g protein.
- Amino Acids: building blocks of proteins. Each contains an amino group
(NH2), a hydrogen atom, an organic acid/carboxyl group (COOH), and a
distinctive side group, all attached to a central carbon atom.
- Side group is a unique structure that differentiates one amino acid from
another.
- The kinds of amino acids, the order in which they are arranged, and the
frequency in which they are used in a chain determines the kind of protein.
- About 20 AAs with 20 different side chains make up most of proteins of living
tissue.
Classification:
Proteins are made up of about 20 common amino acids. Amino acids are classified
as essential (those the body can’t make - that must be supplied by the diet) and
nonessential (can be synthesized in the body).
Essential Amino Acids
Histidine (His) Valine (Val)
Isoleucine (Ileu) Lysine (Lys)
Leucine (leu) Methionine (Met)
Phenylalanine (Phe) Threonine (Th)
Tryptophan (Try)
Non-essential amino acids
Alanine Cysteine Proline
Arginine Glutamic acid Serine
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Asparagine Glutamine Tyrosine
Aspartic acid Glycine
Proteins:
- Cells link AAs end to end in a virtually infinite variety of sequences to form
thousands of different proteins. Each amino acid is connected to the next by a
peptide bond.
- The unique shapes of proteins enable them to perform their various tasks in the
body.
o Hemoglobin – packs the red blood cells and carries oxygen – is made of
four associated polypeptide chains, each holding the mineral iron.
- Heat, acid, or other conditions may disturb proteins’ stability, they undergo
denaturation, in which they uncoil and lose their shapes and, consequently,
their ability to function.
Daily Requirements:
- Many factors determine the requirements (body size, protein quality, new
tissue requirements, stress,…).
- 0.8 g/kg body weight for adults.
- 2.2 g/kg body weight for infants 0-6 months
- 1.6 g/kg for infants 6-12 months.
- 28 g/day for children 7-10 years.
- 71 g/day for pregnant and lactating.
Nutritional Quality of Proteins:
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The protein quality is of great concern, especially in countries where malnutrition
is of great concern. Low quality proteins fail to provide enough of all the essential
amino acids needed to support the body’s work.
Complete Protein:
- Contains the kinds and amounts of essential amino acids to support
maintenance & growth in relatively the same amounts that human
beings require. Generally proteins derived from animals (milk, eggs,
meat, poultry, Fish)
- Gelatin is a exception, it lacks tryptophan and cannot support growth
and health as a diets sole protein.
Partially complete Protein:
- Protein from plants in which one or more essential amino acids are
supplied in amounts inadequate for tissue synthesis (legumes, grains,
nuts)
Incomplete Protein:
- Some plant proteins are notoriously incomplete, in which one or more
of essential amino acids are absent (corn and soy proteins).
High quality protein: an easily digestible complete protein (egg protein, assigned
a value of 100).
Measurement of protein quality:
- Protein Efficiency Ratio (PER) =
Proteins of high quality have a PER of 2.5 or better.
Official method for assessing protein quality, and it is still used to evaluate
proteins for infants by the United States and Canada.
22
Wt gain (g)
Protein fed (g)
- Biological value (BV) is measuring nitrogen content of the food eaten and the
nitrogen content of the urine and feces (protein nitrogen absorbed).
A BV of 70 or more is considered adequate for growth.
Sources:
- Animal sources include milk, eggs, cheese, meat, poultry, and fish.
Protein in these foods provides all the essential amino acids.
- Plant sources are beans, lentils, and other legumes, breads & cereals,
nuts, and seeds. Protein from these sources must be complemented with
another animal or plant proteins.
Functions of Protein:
1. Supporting growth and maintenance.
2. Supplies some energy upon need (4 kcal/g).
3. Supplies essential substances necessary for the construction and proper
functioning of body compounds (enzymes, hormones, regulators of fluid
balance, acid-base regulators, hemoglobin, transporters, antibodies, and others
such as being integral parts of most body structures as skin, bones, and
muscles).
Digestion, Absorption, and Metabolism:
23
The goal of digestion is to release the amino acids that make up the protein
molecule.
Digestion
Mouth Crushed and moistened, mix with saliva
Stomach Protein proteoses peptones
Milk casein calcium caseinate
Small Intestine protein peptones Amino acid
Small intestine in the form of amino acid
- In the stomach:
o HCL uncoils protein strands and activates stomach enzymes
(pepsinogen to pepsin).
o Pepsin cleaves proteins – large polypeptides – into smaller
polypeptides and so AAs.
- In the intestines:
o Pancreatic and small intestinal enzymes split polypeptides further
(tripeptides, dipeptides, and AAs)
o Intestinal proteases hydrolyze peptides and then cells absorb them.
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Gastric Pepsin
Rennin
Trypsin* Erepsin
Absorption
Metabolism
Amino acids
- Build new tissues
- Repair old tissues
- Deamination (if not needed):
Nitrogen removed urea excreted
Carbon, hydrogen, oxygen glucose
Clinical Problems:
Protein excess:
- Protein intake urinary loss of Ca
- protein intake based on increased amount of meat, poultry, whole
milk in the diet will lead to increase intake of saturated fat.
- Protein rich foods are expensive this may lead to exclusion of other
foods that are needed for minerals and vitamins from the diet.
Protein deficiency:
- Nutritional edema
- Reduces the immune response
Protein-energy malnutrition (PEM): a deficiency of protein, energy, or both,
including kwashiorkor, marasmus, and instances in which they overlap.
- Kwashiorkor: older infants and young children (1 to 3 yr). The protein
content of the food is law.
- Acute PEM
- Protein deficiency, illness such as measles or other infection
- Loss of body wt and body fat not as severe as in marasmus, edema
(distinctive feature), belly bulges with a fatty liver.
- Marasmus: Infancy (less than 2 yr). The infant is fed a diet low in
calories and protein.
- Chronic PEM
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- Children look like little old people – just skin and bones, extreme
loss of muscle and fat.
- Muscles including heart waste and weaken.
In all cases, children are likely to develop diarrhea, infections, and multiple
nutrient deficiencies.
Fats
Composition
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- Composed of three chemical elements: Carbon, hydrogen, and oxygen.
- Fat is often used to refer to all the lipids, including triglycerides (fats and oils),
phospholipids, and sterols.
- The triglycerides - composed of one glycerol molecule attached to three fatty
acids – predominate, both in foods and the body.
- Each gram of fat yields 9 kcals.
Fatty acids
- Organic acids – a chain of carbon atoms with hydrogens attached – that has an
acid group (COOH) at one end and a methyl group (CH3) at the other end.
- Some fatty acids have short chains (fewer than 6 carbon atoms), others have
medium length carbon chains (6-10 carbon atom), and the most commonly
occurring in diet has long chains (12-24 carbon atoms).
- Long chain fatty acids include meats and fish; short and medium chains
primarily in dairy products.
- Fatty acids maybe saturated or unsaturated depending on the amount of
hydrogen in their composition.
- Saturated if there is a single bond between the carbon atoms (fully loaded with
hydrogen atoms and contains only single bonds between its carbon atoms).
- Unsaturated if there is a double bond between two carbon atoms (hydrogens
missing and presence of double bonds is an indication of unsaturated fatty
acids).
- One double bound monoustaturated.
- Two or more double bounds polyunsaturated.
Classification of lipids- Triglycerides (the chief form of fat in the diet and the major storage form of fat
in the body; composed of a molecule of glycerol with tree fatty acids attached),
and their component parts, fatty acids (few occur free in foods or in the body).
27
- Phospholipids are fats in which another group has replaced at least one of the
fatty acids.
- Best-known phospholipid is lecithin.
- Each lecithin has a backbone of glycerol with two of its three attachments
sites occupied by fatty acids and a phosphate group with a choline molecule
occupies the third site.
- Unique chemical structure that allows them to be soluble in both water and
fat.
- Part of cell membranes; food industry uses them as emulsifiers.
- Sterols are compounds with a multiple-ring structure. Many vitally important
body compounds are sterols; among them are bile acids, the sex hormones
(testosterone), the adrenal hormones (such as cortisol), and vitatamin D, as
well as cholesterol (most famous sterol that the body makes and uses for its
functioning).
- Cholesterol in the body can serve as the starting material for the
aforementioned compounds.
- Structural component of cell membranes (cholesterol).
Properties- Fats are insoluble in water, but soluble in ether, chloroform, benzene, and
acetone.
- Rancidity (the change in flavor and odor of fats when they are oxidized) occurs
specially in fats that have a high proportion of unsaturated fatty acids.
- Hydrogenated fats are polyunsaturated vegetable oils in which hydrogen has
been added commercially to double bond carbons (monounsaturated and
polyunsaturated fats) making the fats more saturated (solid) and more resistant
to oxidation by a process known as hydrogenation.
- Molecules that remain unsaturated after processing change shape from cis
to trans, trans-fatty acids.
28
- Trans fatty acids have health effects similar to those of saturated fats.
Functions1. Fat foods furnish 9 kcal/g; provide the body with energy.
2. Spare the burning of protein for energy.
3. Provide insulation under skin; help to maintain constant body temperature.
4. Serve as shock absorbers, supporting and cushion vital organs.
5. Facilitate the absorption of fat-soluble vitamins A, D, E, & K.
6. Food fats contribute flavor, palatability, and satiety to the diet.
Essential Fatty AcidsHuman body can make all except two and therefore, must be supplied by the diet:
- Linoleic acid (18-carbon omega-6 fatty acid with 2 double bonds).
- Linoleic acid is converted to arachidonic acid in the body. Arachidonic
acid is required for normal growth, healthy skin, regulation of cell
permeability, strength of capillaries, transport and metabolism of
cholesterol, and as a precursor of prostaglandin.
- Linolenic acid (18-carbonomega-3 fatty acid with 3 double bonds).
- Needed so body can make EPA (eicosapentaenoic acid) and DHA
(docosahexanoic acid).
- These are essential for normal growth and development, and may play an
important role in the prevention and treatment of heart disease,
hypertension, arthritis, and cancer.
- Both, in addition to serving as structural parts of cell membranes, they make
eicosanoids – powerful compounds that help regulate blood pressure, blood
clot formation, and the immune response to injury and infection.
29
Recommended Intakes of FatThere is no daily-recommended allowance for fat. Fats should provide no more
than 30% of the total caloric intake. Other recommendations concerning fats are:
- Reduce saturated fat intake to less than 10% of calories, increase
polyunsaturated fats to about 10% of calories.
- Reduce cholesterol intake to less than 300 mgs daily.
Food sources- Animal sources are whole milk, butter, egg yolk, cheeses, and cream.
- Plant sources are vegetable oil (corn, sunflower, sesame, etc.) and salad
dressings made from oils, nuts, and olives.
Digestion, Absorption, and metabolism of fat
Almost all the digestion of fat occurs in the small intestine. Fat stimulates the
secretion of hormone CCK, which causes the gallbladder to contract so that the
stored bile is released into the small intestine. Bile breaks up the fat into tiny
particles and hold them in suspension in the watery intestinal content: this is
known as emulsification.
30
Digestion
Mouth: No significant action, fats begin to melt (at body temp) Lingual lipase plays a small role in fat digestion
Stomach: fats Fatty acids and glycerol
Small intestine: emulsified fats Monoglycerides, fatty acids aand glycerol
Absorption
Small intestine: Glycerol and fatty acids absorbed into blood
stream
monoglycerides and fatty acids new fat
Metabolism Oxidized for energy Stored in adipose tissue Synthesis of phospholipids
*Pancreatic lipase**Intestinal lipase
In the large intestine: some fat and cholesterol trapped in fiber, exit in feces.
Transport:
The body makes four main types of clusters of lipids and proteins that are used as
transport vehicles for fats. As a group, these vehicles are known as lipoproteins,
and they solve the body’s problem of transporting fatty materials through the
watery blood stream.
31
G. Lipase
P. Lipase*
I. Lipase**
Chylomicrons: They transport diet –derived lipids (mostly triglycerides) from
the intestine to the rest of the body.
VLDL: very low-density lipoprotein: made primarily by the liver cells to
transport lipids to various tissues in the body; composed primarily of
triglycerides.
LDL: low density lipoprotein: derived from VLDL lipoproteins as cells
remove triglycerides from them; chief carrier of cholesterol (bad fat).
HDL: high-density lipoprotein: high in protein: appear to reduce the risk of
coronary heart disease (good fat). Lipoprotein that transports cholesterol and
other lipids back to the liver from the cells for recycling or disposal.
Risk factors associated with increased fat intake:
Obesity
Cardiovascular diseases, Atherosclerosis, stroke, myocardial infarction
Hypertension
Diabetes
Some types of cancer
Energy metabolism
The body’s need for energy:
* The human body requires fuel to do its work. The energy needed for the body
takes priority over the maintenance and building of tissues or the regulation of
body functions.
32
* Glucose-from carbohydrates and glycerol and fatty acids-from triglycerides
provide most of the body’s energy needs. However, if the supply is inadequate
amino acids-from proteins will also be used for energy. Therefore:
* Glucose, fatty acids, glycerol, amino acids + oxygen Energy +
carbon dioxide + water
* The release of energy occurs during a series of pathways that ultimately lead to
the tricarboxylic acid cycle (TCA cycle) and electron transport chain (ETC),
which produce the greatest amount of energy.
* The energy released during catabolism is often captured by go-between
molecules that can easily transfer that energy to other compounds. These
molecules are sometimes called the body’s “common energy currency”, or
“high-energy compounds”. One such compound is ATP.
* Released energy is taken up in tiny packets known as ATP (adenosine
triphosphate). Energy can then be released from these tiny packets by
breaking one of the phosphate bonds, leaving a compound known as ADP.
ADP is rapidly regenerated to ATP.
Units of energy:
* Kcal is used to measure the energy value of the foods. Kcalories are units of
heat energy.
* Joule: mechanical equivalent of heat.
1 kcal = 4.2 kJ 1kJ = 0.24 kcal
Caloric value of nutrients /g
1 g CHO = 4 kcal = 17 kJ
1 g fat = 9 kcal = 37 kJ
1 g protein = 4 kcal = 17 kJ
33
* A bomb calorimeter is an instrument that measures the heat energy released
when foods are burned, thus providing an estimate of the potential energy of
foods.
Components of Energy Expenditure (energy needs of the body):
Heat is released whenever the body breaks down food for energy and again when
that energy is used to do work. The body’s generation of heat is known as
thermogenesis. The total energy a body spends reflects three main categories of
thermogenesis:
1. Basal thermogenesis (basal metabolism).
2. Exercise-induced thermogenesis (physical activity).
3. Diet-induced thermogenesis (thermic effect of food).
A fourth category is sometimes involved – adaptive thermogenesis (energy of
adaptation).
* The total energy requirement of the body includes the basal metabolism,
energy needed for activities, the influence of food, the environmental
temperature, and the special needs for tissue building during growth,
pregnancy and lactation.
* Basal metabolism (BM): energy needs of the body while at rest: includes the
involuntary activities of the body.
* Basal metabolism is the largest component of energy expenditure (about
2/3 of the energy the average person spends).
* It includes bodily activities that we can’t control. Examples are breathing,
heart beating, circulation of blood, peristaltic movements of the intestinal
tract, and the metabolic activities – in short, they support all the basic
processes of life.
* The basal metabolic rate (BMR) is the rate at which the body spends energy for
these maintenance activities. The rate may vary from one person to another.
34
* BMR is regulated by the thyroid gland.
Factors affecting BMR:
* Body size: Greater skin surface loses more heat.
* Age: Lean body mass diminishes with age, slowing the BMR.
* Height: In tall, thin people, the BMR is higher.
* Sex: BMR is 10% higher in men than in women
* Muscle mass and body fat: athletes have higher rate than the non-athlete (the
more the muscles mass the more heat loss).
* Fever: fever elevates BMR. For each degree increase in body temperature the
BMR increases 13%.
* Stresses: Raises the BMR (including many diseases and certain drugs).
* Environmental temperature: Both heat and cold raise the BMR.
* Fasting/starvation: Lowers the BMR.
* Malnutrition: Lowers the BMR.
* Hormones: The thyroid gland hormone thyroxin, for example, can speed up or
slow down the BMR.
* Growth: Building new tissues accounts for a high rate of BMR in infants.
Increase in metabolism during the growth period of adolescence and also for
the development of the fetus during the second and third trimesters of
pregnancy. Therefore, in children and pregnant women, the BMR s higher.
* Smoking: Nicotine increases energy expenditure.
* Caffeine: increases energy expenditure.
* Sleep: BMR is lowest when sleeping.
Diet-Planning Guides:
Diet planning is the bridge between nutrition theory and the food on the table. To
plan a diet that achieves all of the dietary ideals, a person needs tools as well as
knowledge. To help people plan diets, two most widely kinds of guides are
available:
1. Food group plans (FGP):
35
- The U.S. Department of Agriculture (USDA) released a new food guide,
MyPlate, to replace the Food Guide Pyramid.
- Describes the daily number of servings recommended for gender and age
groups.
- The five-food group (MyPlate) is part of a larger communication initiative
based on 2010 Dietary Guidelines for Americans to help consumers make
better food choices.
- The plan can provide a reasonable foundation for diet planning.
- For information on what’s in each group, how much is needed, what counts as
a cup, and health benefits, visit www.Choose MyPlate .gov .
Problems with the five food groups- It does not specify calorie amount.
- A person may fail to meet the daily needs for some nutrients.
- It ignores the needs of vegetarians.
In general food group plans organize foods by their nutrients and origins to
provide patterns of food intake that cover nutrient needs.
2. Exchange lists :
- Lists of foods that can be used with food group plans to help achieve kcalorie
control and moderation.
- The system sorts foods into three main groups by their proportions of
carbohydrate, fat, and protein and specifies their portion sizes.
- Provides a sense of which foods are similar to each other in their energy and
selected nutrient contents.
- Can facilitate weight control, controls fat intake (saturated vs.
polyunsaturated), fiber and salt intakes for preventing many diseases
36
- Organizes foods into three main groups according to their CHO, fat and protein
contents (and therefore, total energy content as well). Foods on any single list
can be used interchangeably.
Problems with the exchange system:
- It pays strict attention to portions.
- Foods are based on their content of CHO, fat, protein and not their content of
vitamins and minerals.
In general exchange system facilitates kcalorie control because foods on each list
provides approximately equal amounts of carbohydrate, fat, and protein, as well
total kcalorie.
Dietary guidelines for disease prevention:
Eat a variety of foods
Maintain healthy weight
Choose a diets low in fat, saturated fat, and cholesterol
Choose a diet with plenty of vegetables, fruits, and grain products
Use sugar in moderation
Use salt and sodium in moderation
37
38
Glucose
Pyruvic AcidAmino Acid
PROTEIN
Glycerol FAT
Acetyl CoA Fatty Acid
TCACycle
CO2 H2OEnergy
NH2
NH2
CARBOHYDRATE
Exchange List for Meal Planning--------------------------------------------------------------------------------------------------------
Groups/Lists Carbohydrate Protein Fat Calories (grams) (grams) (grams)
--------------------------------------------------------------------------------------------------------
CARBOHYDRATE GROUP:Starch 15 3 -- 80Fruit 15 -- -- 60Milk, skim 12 8 -- 90Milk, reduced fat 12 8 5 120Milk, whole 12 8 8 150Other Carbohydrates 15 varies varies variesVegetables 5 2 -- 25
MEAT AND MEAT SUBSTITUTE GROUPVery lean -- 7 0-1 35Lean -- 7 3 55Medium-fat -- 7 5 75High-fat -- 7 8 100
FAT GROUP -- -- 5 45
_____________________________________________________________________
(ADA & A Diet A, 1995)
39
Nutrition AssessmentNutritional assessment evaluates a person’s health from a nutrition perspective.
Many factors influence or reflect nutrition status. Therefore, nutritional assessment
includes:
Anthropometric measurments.
Physical examinations (clinical assessment).
Historical information (dietary assessment).
Biochemical analyses (laboratory evaluations).
Anthropometric Measurments
Anthropometrics are physical measurments that reflect body composition and
development.
Height
Weight
Skinfold
Circumferences
Height:
Malnutrition and certain illness during growing period can prevent an
individual from reaching optimal height.
Best obtained with standing straight with the back to a measuring device
attached to a vertical surface.
For infant and very young children recumbent (lying down) length is
measured.
Weight:
Measured using a beam-balance (preferred) or electronic scales – most
accurate types.
40
Pediatric scale is used for measuring the weight of infants and children too
young to stand.
Body mass index:
An index of a person’s weight in relation to height, which is useful for estimating
the risk to health associated with malnutrition.
BMI = Weight, kg / Height, m2
BMI < 18.5 = underweight
BMI 18.5 to 24.9 = normal
BMI 25 to 29.9 = overweight
BMI 30 = Obese
Skinfold/fatfold Measures:
Means for assessing the energy reserves in the form of fat.
Help distinguish between professional athletes and overweight individuals.
Triceps (TSF) and subscapular (SSF) measurements are most frequently taken.
Measurements are conducted using a caliper.
Other Measures of Body Fat and Lean Tissue:
Waist Circumference
Waist-to Hip Ratio
Hydrodensitometry
Bioelectric Impedance
Clinicians use many other methods to estimate body fat and its distribution.
Physical Examinations (clinical assessment)
Physical examinations are used to search for signs of nutrient deficiency or
toxicity.
41
Many signs appear most rapidly in parts of the body where cell replacement
occurs at a high rate
Such as in the skin, hair, eyes, and digestive tract (including the mouth and
tongue), which are most frequently examined for possible nutritional
deficiencies.
The epithelial and mucosal cells have a rapid turnover rate so symptoms of
deficiencies may appear earlier.
Advantages: non-threatening, easy to obtain, most informative and
communicate much information about nutrition health.
Disadvantages: many physical signs are nonspecific; they can reflect any of
several nutrient defeciencies as well as conditions not related to nutrition.
Historical Information (dietary assessment)
Clues about present nutrition status become evident with a careful review of a
person’s historical data. Historical data used in nutrition assesments includes the
following:
Health history: current and previous health problems and family health
history that affect nutrient needs, nutrition status, or the need for
intervention to prevent health problems.
Socioeconomic history: personal, cultural, financial, and environmental
influences on food intake, nutrient need, and diet therapy options.
Drug history: mediations, dietary supplements, and alternative therapies
that affect nutrition status.
Diet history: nutrient intake excesses or deficiencies and reasons for
imbalances.
Evaluation of the diet history provides a record of a person’s eating habits and
food intake and can help identify possible nutrient imbalances.
42
Food choices are an important part of lifestyle and often reflect a person’s
thoughts.
Methods for collecting intake information includes the following:
1. 24-hour recall: The easiest and the most common methods of obtaining dietary
information. Provides data for one day only, in which the assessor asks the
client to recount everything eaten or drunk in the past 24 hours or for the
previous day.
Disadvantages:
Patient may not be able to recall the foods eaten.
Patient may not be able to estimate the amount of food eaten.
Patient may not be telling the truth.
The intake may not be a typical one.
2. Food frequency questionnaire:
A checklist of foods on which a person can record the frequency with ehich
he or she eats each day.
Helps pinpoint food groups and therefore, nutrients that may be excessive
or deficient in the diet.
Does not provide information on the quantities.
Useful when used with the 24-hour recall, enabling the assessor to double
check the accuracy of the information obtained.
3. Food record:
An extensive, accurate log of all foods eaten over a period of several days or
weeks, including the quantity and method of preparation. A food record that
includes associated information such as when, where, and with whom each food is
eaten is sometimes called a food diary.
43
4. Observation of food intake:
Members of the care team can obtain information about food intake and factors
affecting it in the hospital and at home through observing the clients.
5. Usual intake: An assesor asks questions about a person’s usual intake until a
typical daily pattern emerges.
Useful especially in verifying food intake when the past 24 hours have been
atypical, as well as helps the assesor verify food habits.
Difficult for a person whose diet intake varies widely from day to day.
Nutrition History:
Collect information on the general pattern of food intake and other factors
influencing the patient’s food habits.
Includes 24-hour recall, a food frequency list, an extensive interview and
through reading the patient’s medical record.
Estimating nutrient content of the diet:
Dietary intake is evaluated by comparing it to some standards
Biochemical Analyses (laboratory assessment)
Biochemical analyses help to determine what is happening to the body internally.
Common tests are based on analysis of blood and urine samples, which contain
nutrients, enzymes, and metabolites that reflect nutrition status. Low nutrient
concentrations in the blood may occur due to inadequate intake, impaired
absorption, transport, or metabolism, increased excretion, or combinations of the
above.
Nutrient levels including glucose, lipids, or minerals, hemoglobin, hematocrit,
erythrocyte, leukocyte, etc. counts are used to measure nutrient levels.
44
Low Hb can be obsereverd in cases of anemia, hemorrhage, and protien-energy
malnutrition while elevated in dehydration.
WBC may increase in cases of infections and leukemia
RBC counts would decrease in anemia, chronic infectious diseases and
hemorrahage and are elevated in dehydration.
Serum albumin and serum transferrin are depressed in protein malnutrition
Decreased lymphocyte counts are associated malnutrition, stress, trauma, and
lowered immune response.
Vitamins
45
- Vitamins are organic essential nutrients containing carbon, oxygen, and other
elements that are required in tiny amounts for body processes, including
functions that promote growth, reproduction, or the maintenance of health and
life.
- Vitamins do not provide energy but they enable the body to use the energy
provided from fats, carbohydrates, and proteins.
- Vitamins are found in minute amounts in natural foods. Eating a balanced diet
can provide all the vitamins needed.
- Vitamin deficiencies can occur if the diet is not balanced, or if so much alcohol
is used. Just as an inadequate intake can cause harm, so can an excessive
intake.
- The amounts of vitamins people ingest daily from foods and the amounts they
require are measured in micrograms or milligrams, rather than grams.
Hypervitaminosis: excess of one or more vitamins.
- Vitaminosis means without vitamins. This word followed by the name of a
specific vitamin is used to indicate a serious lack of that particular vitamin.
Preserving vitamin content in food (minimize nutrient loss):
- Buy the freshest, unbruised vegetables and fruits.
- Use raw vegetables and fruits whenever possible.
- Prepare fresh vegetables and fruits just before serving.
- Heat canned vegetables quickly and in their own liquid.
- Follow package directions when using frozen vegetables or fruit.
- Use as little water as possible in cooking (boil water).
46
- Save the cooking liquid for later use in soups, stews…..etc.
- Store fresh vegetables and fruits in a cool dark place.
Classification of vitamins:
- Vitamins are grouped according to solubility. Vitamins A, D, E, and K are fat-
soluble while the B vitamins and vitamin C are water-soluble.
- Vitamins A and D are sometimes classified as hormones, and B vitamins can
be classified as catalysts or co-enzymes that assist certain enzymes in the
release of energy from food.
Fat-soluble vitamins:
- They require bile for their absorption due to being insoluble in water.
- They travel through the lymphatic system within chylomicrons before entering
the blood stream, where many of them require protein carriers for their
transport.
- Absorbed fat-soluble vitamins are stored primarily in liver and adipose tissue;
therefore deficiencies of these vitamins are slower to appear.
- Mega-doses of these vitamins can be toxic (since they are stored in liver).
Vitamin A:
Found in 2 forms
1. Active in the body: vitamin A “retinol, retinal, retinoic acid”.
2. Precursors of vitamin A: provitamin A, “Carotenoids”. Beta-carotene is
the most studied and greatest vitamin A activity.
Functions:
- Essential for maintaining healthy eyes (promoting vision), skin (participating
in protein synthesis and cell differentiation), and supporting reproduction and
bone and tooth growth.
47
- Aids in the prevention of infections by helping to maintain healthy mucus
membranes.
Sources:
- Retinoids are found in fat-containing animal foods, such as liver, fish liver oils,
butter, cream whole milk, cheeses (from whole milk) and egg yolk.
- Carotenoids are derived from plant foods such as yellow and dark green leafy
vegetables, in yellow and orange fruit.
Deficiency:
- Night blindness: slow recovery of vision after flashes of bright light at night or
an inability to see in dim light.
- Blindness: progressive blindness caused by severe vitamin A deficiency.
- Dry, rough skin (keratinization), epithelial tissues weaken, and decreased
mucus secretion.
- Increased susceptibility to infections: measles, pneumonia, severe diarrhea,
malaria, lung disease etc.
Vitamin D:
- Found in 2 forms:
D2 (ergocalciferol) and D3 (cholecalciferol).
- Different from all other nutrients in that the body can synthesize it, with the
help of sunlight, from a precursor that the body makes from cholesterol. Given
enough time in the sun, people need no vitamin D from foods.
- D3 is formed in humans by the sun’s ultraviolet rays that hit the precursor in
the skin.
- D2 formed is the plant version.
- Vitamin D is a prohormone because it is converted to a hormone in the human
body; vitamin D is heat stable and not easily oxidized.
Functions:
- Mineralization of bones including the teeth
48
- Promote calcium and phosphorus absorption from the GI tract
- Regulation of calcium and phosphorus levels in the blood
The bones grow stronger and denser as they absorb and deposit these minerals.
Vitamin D is the director, but the star of the show is calcium.
Sources:
- Synthesized in the body through exposure to sunlight
- Food sources of vitamin D include fortified milk, butter, egg
yolks, liver, fatty fish and their oils, and fortified margarine.
Deficiency:
- Decreased calcium and phosphorus absorption (low production of the protein
that binds calcium), which results in poor bone and tooth formation due to
being undersupplied.
- Young children develop rickets (growth retardation and skeletal deformities) -
bowed legs are often the most obvious sign.
- Adults develop osteomalacia (softening of bone).
- Osteoporosis is a condition of reduced bone density (a disease characterized by
brittle, porous bones). Inadequate vitamin D sets the stage for a loss of calcium
from the bones, which can result in fractures.
Vitamin E:
- Called tocopherols. Alpha-tochopherol is the only active vitamin E in the
human body.
- It deteriorates when exposed to heat.
Functions:
- Acts as an antioxidant
1. Protection of cell structure from the adverse effects of free radicals.
2. Prevents the oxidation of PUFA, but it protects other lipids and vitamin A.
- Improves physical performance, enhances sexual performance, or cures sexual
dysfunction in males.
49
Sources: wheat germ, vegetable and seed oils, leafy green vegetables, nuts,
and margarine. (Animal foods are poor sources of vitamin E).
Deficiency:
- Primary symptom: increased rate of hemolysis in the RBCs (erythrocyte
hemolysis), due to oxidation of PUFA in their membranes
- Anemia
- Neuromuscular dysfunction involving the spinal cord and retina of the eye.
Vitamin K
Functions:
- Acts primarily in synthesis of blood clotting proteins.
- Synthesis of bone proteins that regulate blood calcium.
Sources:
- Billions of bacteria in the GI tract (mainly in small intestines) make the
vitamin; this source provides about half of a person’s needs.
- Other half from: rich foods include green leafy vegetables, liver, and members
of the cabbage family, fruits, cereals, and milk.
Deficiency:
- Defective blood coagulation (Hemorrhaging, uncontrolled bleeding).
50
Water-soluble vitamins:
- Include B vitamins and vitamin C.
- Absorbed directly into the blood.
- Dissolve in water; circulate freely in water filled parts of the body.
- Not stored in the body; kidneys detect and remove excess in urine.
- Possible to reach toxic levels when consumed from supplements.
Reminder – key info:
Several B vitamins form part of coenzymes that assist certain enzymes in
the release of energy from carbohydrate, fat, and protein.
A coenzyme is a small organic molecule that associates closely with certain
enzymes; many B vitamins form integral parts of coenzymes.
B1 (Thiamin):
Functions: part of coenzyme TPP (thiamin pyrophosphate) used in energy
metabolism of all cells.
Sources: whole-grain, fortified, or enriched grain products; moderate amount in
all nutritious food.
Deficiency:
- Loss of appetite (anorexia), fatigue, nervous irritability and constipation.
- Extreme deficiency causes the disease beriberi (characterized as wet, with
edema or dry, with muscle wasting), a disease that affects the nervous system,
heart and other muscles.
B2 (Riboflavin):
- sensitive to light
Functions:
- Essential for carbohydrate, fat and protein metabolism.
51
- Part of coenzymes FMN (flavin mononucleotide) and FAD
(flavin adenine dinucleotide) used in energy metabolism.
Sources: milk products (yogurt, cheese); enriched or whole grains; organ meats;
dark green leafy veg.
Deficiency: Ariboflavinosis: inflammation of the members of the mouth, skin,
eyes, and GI tract.
Cheilosis is sores on the lips and cracks at the corners of mouth.
Dermatitis; eye sensitivity (burning, itching).
B3 (Niacin):
Other names: nicotinic acid, nicotinamide
- Stable in foods, stand reasonable heat, acid and storage.
- Functions:
- Serves as coenzyme in energy metabolism.
- Part of coenzyme NAD and NADP used in energy metabolism.
Sources: meats, poultry, fish and peanuts, whole grain and enriched breads
and cereals, and all protein containing foods.
- Tryptophan (an amino acid) is a precursor of niacin. The body can
make it from the amino acid tryptophan; 1 mg niacin equals 60 mgs
tryptophan.
52
Deficiency:
- Essential for the prevention of pellagra, a disease that produces the symptoms
of diarrhea, dermatitis, dementia, and eventually death (often called “the four
Ds”).
- Other deficiency symptoms include blurred vision, abdominal pain, inflamed
tongue, depression, fatigue apathy.
Biotin:
Functions and sources:
- Part of a coenzyme used in energy metabolism, fat synthesis, amino acid
metabolism, and gluconeogenesis.
- Widespread in foods; organ meats, egg yolks; also produced by GI bacteria.
Requirements: needed in very small amounts
Deficiency: skin rash, hair loss, and neurological impairment (consumption of
raw egg whites, more than two dozens every day for several weeks, which contain
a protein than binds biotin and prevents its absorption).
Pantothenic acid:
Functions: Part of coenzyme A, used in energy metabolism.
- Involved in the more than 100 steps in the synthesis of lipids,
neurotransmitters, steroid hormones, and hemoglobin.
Sources: Widespread in foods; organ meats, poultry, mushrooms, avocados,
broccoli, whole grains.
53
Deficiency: Its symptoms involve a general failure of all the body’s systems and
include fatigue, GI distress, and neurological disturbances.
Vitamin B6:
Occurs in three forms - pyridoxine, pyridoxal and pyridoxamine.
Functions: part of coenzyme PLP (pyridoxal phosphate) used in amino acid
metabolism.
Enhances the conversion of tryptophan to niacin and to serotonin;
also to make red blood cells (heme, nonprotein portion of
hemoglobin).
Sources: fish, poultry, meats, potatoes, a few other vegetables (green)
including legumes, and fruits (purple) including noncitrus
ones, and fortified cereals.
Deficiency: early symptoms include depression, confusion; advance symptoms
include abnormal brain wave patterns and convulsions; scaly
dermatitis and anemia (small cell type – microcytic)
are other symptoms.
Folate: also known as folic acid or folacin, and chemical name is pteroylglutamic
acid (PGA).
- Destroyed by storage, processing, heat or oxidation.
Functions:
- Part of coenzyme THF (tetrahydrofolate) and DHF (dihydrofolate) used in
DNA synthesis and therefore in new cell formation.
54
Sources: fortified grains, green leafy vegetables, legumes (black beans,
kidney beans, and black eyed peas), liver and seeds.
Requirements: Adults: 400 g/d
Deficiency: Impairment of cell division and protein synthesis – processes
critical to growing tissue.
Two of the first symptoms are anemia and GI tract
deterioration. “megaloblastic anemia”, a condition in which
RBCs are large and immature, and unable to carry oxygen
properly.
Elevated homocysteine, which is an amino acid that cannot be
broken down without adequate folate
B12: (Cobalamin)
Functions: Vitamin B12 and folate are closely related: each depends on the
other for activation.
Part of coenzyme methylcobalmin and deoxyadenosylcobalamin
used in new cell synthesis; helps to maintain nerve cells;
reform folate coenzyme.
Sources: Animal products: meats, fish, poultry, eggs, dairy products, and
fortified cereals.
Deficiency: Most reflect inadequate absorption, not poor intake due to two
reasons: a lack of HCL or intrinsic factor.
55
Deficiency disease, pernicious anemia, is caused by atrophic
gastritis and a lack of intrinsic factor, and is characterized by
abnormally large immature red blood cells.
Deficiency symptoms include anemia of folate deficiency, sore
tongue, fatigue, and degeneration of peripheral nerves progressing to
paralysis.
Vitamin C (Ascorbic acid):
- Anti-oxidant properties (protects food from oxidation and defends body from
free radicals).
- Readily destroyed by heat, air alkalis.
Functions:
1. Enhances iron absorption.
2. Collagen synthesis (a fibrous structural protein that strengthens blood
vessels, forms scar tissue, provides matrix for bone growth).
3. Antioxidant, by losing its electrons to defend against free radicals.
4. Synthesis of hormones, including thyroxin.
5. Metabolism of amino acid.
6. Strengthens resistance to infection.
Sources: Citrus fruits, tomatoes, potatoes, melon, strawberries, magoes,
cabbage-type vegetables, and dark green vegetables (such as
broccoli and bell peppers).
56
Deficiency:
- Scurvy (a disease characterized by spongy and bleeding gums, loose teeth,
sore joints and muscles. Symptoms of the disease includes bruises, poor
wound healing, easily fractured bones).
- Symptoms include bleeding gums, loose teeth, bruises and rough skin, poor
wound healing, anemia and infection.
57
Minerals- Minerals are inorganic substances found in all body tissues and fluids.
- They do not furnish energy and are stable in water.
- Minerals are divided into two classes
Major minerals (macrominerals) are those that occur in largest amounts in foods
and in the body. Examples are Calcium, Phosphorus, Sodium, Potassium,
Chloride, Magnesium, and sulfur.
Trace minerals (microminerals) are those that occur in very small amounts in
foods and in the body. Examples are Iron, Iodine, Zinc, Selenium, Fluoride,
Copper, and Manganese.
General Functions:
- Bone and tooth formation
- Constituents of soft tissues, vitamins, enzymes, and hormones
- Nervous response and muscle contraction
- Water and acid-base balance
Dietary allowance:
- RDA for eight of the elements is set
- For other minerals a “safe and adequate” range of intakes has been
recommended.
- Based on weight, the allowance for infants, children, and teenagers are
higher to allow for growth.
- Allowances are also higher for pregnancy and lactation.
Factors that affect the absorption of minerals:
- Body need
- The chemical form of the mineral
58
- Stomach acidity
- Lactose improves Ca absorption
- Ascorbic acid enhance the absorption of Ca, Fe, Zn
- Some drugs and excess fiber bind minerals
- Laxatives and diarrhea decrease absorption
- Excess of some minerals decrease the absorption of other minerals
- Damage to the intestinal mucosa interferes with the absorption of minerals
MINERALS FOOD SOURCES FUNCTIONS DEFICIENCY
Major
minerals
Calcium
MilkCheeseSome dark green,
leafy vegetables
- Normal development and maintenance of bones and teeth
- Clotting of the blood - Nerve irritability- Normal heart action- Normal muscle activity - Activates enzymes
- Retarded growth- Poor tooth and bone
formation- Slow clotting time- Osteoporosis
Phosphorus Milk and CheeseLean meatPoultryFishWhole grain cerealsLegumesNuts
- Normal development and maintenance of bones and teeth
- Maintenance of normal acid-base balance of the blood
- Constituent of all body cells
- Necessary for effectiveness of some vitamins
- Poor tooth and bone formation
- Weakness- Pain in bones
Magnesium AvocadosNutsMilkWhole grainsGreen, leafy vegetablesLegumesBananas
- Constituent of bones, muscles and red blood cells
- Regulate the transmission of nerve impulses and activate enzymes including those involved in energy metabolism
- Severe prolonged vomiting
- Kwashiorkor severe malabsorption disease
- Impair central nervous system activity
59
MINERALS FOOD SOURCES FUNCTIONS DEFICIENCY
Sodium Table saltMeatMilk and cheeseSoy sauceProcessed foods
- Water balance & osmotic pressure
- Acid-base balance- Transmission of nerve
impulse- Muscle contraction- Cell permeability
- Nausea- Exhaustion- Muscle cramps
Potassium VegetablesFruits, especially oranges, Bananas, and prunes
- Osmosis- Fluid balance- Regulate muscle
contraction including heart muscle
- Cell metabolism
- Muscle weakness- Paralysis- Confusion- Abnormal heart
beats
Chloride Table saltMeatMilkEggsProcessed foods
- Osmosis- Fluid balance- Acid-base balance- Formation of
hydrochloric acid
- Do not occur in normal conditions
- Nausea- Exhaustion
Sulfur All protein containing foods (meat, poultry, fish, eggs)
- For building hair, nails, and all body tissues
- Constituent of all body cells
- Metabolism
- Unknown (no deficiency has been observed)
60
MINERALS FOOD SOURCES FUNCTIONS DEFICIENCY
Trace
Minerals
Iron
Red meatsFishPoultryShell fishEggsLegumesDried fruits
- Essential for formation of hemoglobin of the red blood cells and provision of oxygen to cells
- Constituent of cellular enzymes
- Anemia: Characterized by weakness, dizziness, reduced resistance to infection, loss of weight, and pallor
Copper SeafoodLegumesNutsWhole grain Cereals
- Essential for formation of hemoglobin and red blood cells
- Component of several enzymes
- Anemia- Diarrhea- Liver damage
Iodine SeafoodFoods grown in soil bordering salt waterIodized salt
- Formation of hormones in thyroid gland that help to regulate growth development, and metabolic rate
- Goiter (enlargement of the thyroid gland)
- Cretinism (a congenital disease characterized by mental and physical retardation)
Manganese
Whole grainsNutsVegetables
- Cofactor for several enzymes - Unknown
Zinc Protein containing foods:Seafood, especially oystersLiverMeatEggsMilk
- Component of insulin and many enzymes
- Involved in making genetic material and proteins
- Immune reactions- Transport of vitamin A- Wound healing- Taste perception- The making of sperm- Essential for growth
- Growth failure in children
- Loss of appetite- Skin changes
(dermatitis)- Impaired wound
healing- Loss of taste- Sexual retardation
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Fluoride Fluoridated waterSeafood
- Helps form bones and teeth; confers decay resistance on teeth
- Susceptibility to tooth decay
Cobalt Organ meatsMuscle meatsMilkEggs
- A component of vitamin B12 necessary for formation of the red blood cells
- Unknown
Selenium SeafoodsOrgan meatsOther meatsWhole grainSome vegetables
- Part of an enzyme that defends against oxidation
- Regulates thyroid hormone
- Associated with Keshan disease (predisposition to hear disease characterized by cardiac tissue becoming fibrous
Chromium MeatsUnrefined grainsVegetable oils
- Associated with insulin- Needed for energy
release from glucose
- Unknown
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WaterIn the body, water becomes the fluid in which all life processes occur. Water
constitutes about 60 percent of an adult’s body weight and a higher percentage of a
child’s. Water content is the highest in metabolically active tissues (muscles)
Functions:
* Component of most cells
* Regulate body temperature
* Act as lubricants around joints
* Elimination of waste products
* Act as a media for the chemical reactions
* Transport of nutrients to the tissue
* Serves as a solvent for mineral, vitamins, amino acids, glucose
and other molecules
Sources of water:
* Fluids (water, tea, coffee)
* Solid foods
* Metabolic water
Requirements:
* Insufficient data to establish EAR or RDA for Water
* Insufficient data available to make recommendations based on reduction of
chronic risk diseases
* BW can be lost quickly from PA and heat
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Recommended