Upload
lindsay-carson
View
222
Download
0
Tags:
Embed Size (px)
Citation preview
Topic A.1: Components of the Human Diet
Page 208
Nutrients
• Chemical substance found in foods and used in the human body
• Absorbed to give you energy, strengthen bones, prevent you from getting a disease (vitamins)
• Some amino acids and lipids can be synthesized by the body, many cannot– So, we get these from foods
Essential Nutrients
• Nutrients obtained from foods because your body cannot synthesize them
• Examples: – Essential amino acids– Essential fatty acids– Minerals– Most vitamins– Water
• Carbohydrates are not essential nutrients b/c it is possible to live on diets with little to no carbohydrates – Not highly advised …
Amino Acids
• 20 amino acids proteins
• Nine of these amino acids cannot be synthesized in the body– The human genome lacks the DNA sequence– Referred to as essential amino acids
• The other 11 can be manufactured in the body; called nonessential amino acids
Protein Deficiency
• Deficiency– A person is not getting enough of a certain nutrient – This causes a health problem
• Protein deficiency– Can lead to insufficient production of blood plasma
proteins– Retention of fluids in certain tissues
• Notably the walls of the intestine
– Example of malnutrition
Malnutrition
• Imbalance in the diet which leads to one or more diseases – Typically caused by a deficiency; in some
circumstances, caused by an excess of one or more essential nutrients
• Example: Kwashiorkor Disease– Common in children in non-industrialized countries – Name comes from Ghana– A second born child receives milk from his mother,
but leaves little to no milk for the first born – First born may develop Kwashiorkor (protein
deficiency)
Kwashiorkor
• Symptoms include: – Fatigue, growth failure,
loss of muscle mass edema, decreased immunity
• Complications: – Coma, shock,
permanent mental and physical disability
A Simple Cure … ?
• Eat more protein
• However, sources of protein are expensive– Not an easy option for many families
• Humanitarian efforts – High protein biscuits – Teach people how to raise chicken – Introduce eggs into diets
Turn and Talk
• To what degree do you think the following are factors in malnutrition? – Poverty and wealth– Cultural differences concerning dietary preference– Climatic conditions – Poor distribution of food (i.e. insufficient roads,
bridges, railways) – A nomadic lifestyle– Corrupt politicians misusing agriculture or aid money– Lack of health care leading to a cycle of disease and
poverty
PKU
• Genetic disease caused by a mutated gene• The gene codes for a specific enzyme which
converts the amino acid phenylalanine to tyrosine
• People with PKU cannot convert phenylalanine into tyrosine, so they have very high levels of phenylalanine – This affects brain development– Untreated PKU severe mental problems and
learning difficulties
Solution
• PKU can be diagnosed early with a blood test at birth
• Parents can be informed what treatment if necessary– Common to follow a diet low in protein to
avoid phenylalanine (eliminate milk, peanuts, cheese, meat)
– Aspartame contains phenylalanine (one reason to label all food products)
Fatty Acids
• Not all fats are created equal
• What is the same: – Carboxyl group (COOH)– Methyl group (CH3) – Hydrocarbon tail (in the middle)
• See figures on pages 210-211– 7.1, 7.2, 7.3
Saturated Fatty Acids
• Saturated with hydrogen atoms
• No double bonds between the carbon groups
• The shape is straight – no kinks
• Animal products: – Bacon, butter, fat in red meat– Generally solid at room temperature
• Eat in extreme moderation …
Monounsaturated Fatty Acids
• If one double bond exists in the chain of hydrocarbons, the fatty acid is NOT saturated – Monounsaturated fatty acids
• Two or more double bonds … – Polyunsaturated fatty acids– Typically comes from plants
• Olives, avocados, nuts
– Tend to be liquid at room temperature
Cis vs. Trans fatty acids
• In some processed foods (snacks, cake), polyunsaturated fats are hydrogenated
• This means the double bonds are eliminated by adding hydrogen atoms – Straightens out the natural bent shape– Naturally curved fatty acids are called cis – The hydrogenated fatty acids are called trans
• AVOID TRANS FATS!!
Omega 3 Fatty Acids
• Example of cis fatty acids – Healthy– Good for your brain and heart– Salmon, sardines,
mackerel (fish)
Diets rich in fats
• The shape is important• Fatty acids that are curved are more easily
picked up in the current of the blood stream
• Straight fatty acids can lie flat against the walls– Deposits combine with cholesterol to form
plaque – Inner lining of blood vessels
Plaque
• Reduces blood flow
• A chunk may break off, get lodged, so no blood can pass through
• If this happens in the heart (heart attack)
• If this happens in the brain (stroke)
So, about eating fats
• A diet rich in saturated fats has a much higher chance of leading to serious cardiovascular problems later in life
• Diets rich in polyunsaturated fats lead to lower quantities of plaque– Also tend to carry cholesterol away
• Both types have high amounts of energy (CALORIES), so consuming a lot of either type is unhealthy
So, take away message
• When you eat, look at the food labels
• Look for cholesterol, saturated fatty acids, polyunsaturated acids, and trans fat
• Your body needs healthy fat to function, but focus on eating a balanced diet
• Cardiovascular disease is also influenced by genetics, amount of exercise, and smoking
Vitamins and minerals
• Often grouped together, but structurally very different
• Minerals are inorganic– Does not contain carbon– Not synthesized by organisms– Rocks, soil, or sea water
• Vitamins are organic – Synthesized in plants and animals – Contain carbon
Examples
• Minerals: – Sodium, calcium, iron
• Vitamins: – Vitamin A, C, D, ...
– Both are needed in very small amounts (we’re talking milligrams)
– Both prevent dificiency diseases
Vitamin C
• Recommended level 30-60 mg per day– Check your food labels
• Vitamin C protects against infection, wound healing, and maintaining healthy gums, teeth, bones and blood vessels – Excess vitamin C can lead to kidney stones – Too little vitamin C can cause scurvy
• Fluid retention, loss of teeth, bleeding into joints, and anemia
• Untreated may be fatal
Vitamin D
• Formation of bones
• Insufficient supply of vitamin D may cause rickets.– Deformities in the bones – Children with rickets do not reach optimal
height; legs are often bowed inward or outward at the knees (see picture on page 216)
Vitamin D
• Sources: – Exposure to sunlight– Food (fish: salmon, tuna, sardines; eggs, liver,
milk and cereal are often fortified) – Vitamin supplements
• Risks? – Exposure to sun UV radiation (may cause
sunburn and skin cancer called malignant melanoma)
Dietary Supplements
• May be taken if the foods you eat do not provide you with vital minerals and nutrients
Iodine
• Iodine is a component of thyroxin, a hormone made by the thyroid gland– Regulates growth
• Too little iodine inflammation of the thyroid gland– This is called a goiter– Babies may suffer from growth and mental
retardation
Why don’t we see a lot of goiters in industrialized countries?
• Iodine is added to salt
• US; 1924
• By the 1950s, goiters were essentially nonexistent in the US
Fiber
• “Roughage” – provides bulk • Cellulose in plant material• Reduces likelihood of constipation and chances
of intestinal problems like colon cancer • Also links to reduced cardiovascular disease
– Toxins bind to fiber and carried out of the body
• Links to managing body mass fiber helps you feel fuller longer
• Many people do not get the amount of fiber they need on a daily basis.
Take away message
• So what are some of the foods you should be eating? Why?
• What are foods you should avoid, or eat in moderation? Why?