SOURCES OF SOURCES OF ENERGY :MACRONUTRIENENERGY :MACRONUTRIEN

TT- - Macronutrients include:Macronutrients include: Carbohydrates.Carbohydrates. Fats.Fats. Proteins.Proteins.

- Carbohydrates and Fats are the - Carbohydrates and Fats are the principal energy sources.principal energy sources.

- Dietary proteins serve many roles - Dietary proteins serve many roles including energy production.including energy production.

FACTORS EFFECTING FACTORS EFFECTING ENERGY EXPENDITUREENERGY EXPENDITURE

- - There are four principal factors that affect There are four principal factors that affect individual energy expenditure:individual energy expenditure:

Surface areaSurface area (which is related to height and (which is related to height and weight)weight)

AgeAge (reflects growth and lean muscle mass)(reflects growth and lean muscle mass) SexSex (women have a lower BMR due to lower (women have a lower BMR due to lower

% of lean muscle mass and the effects of % of lean muscle mass and the effects of female hormones on metabolism).female hormones on metabolism).

Activity level :Activity level :The long term effect is more The long term effect is more important than the immediate one .It leads important than the immediate one .It leads to an increase in lean muscle mass and to an increase in lean muscle mass and hence BMR. hence BMR.

EFFECT OF BODY EFFECT OF BODY COMPOSITION ON BMRCOMPOSITION ON BMR

Acceptable Macronutrient Acceptable Macronutrient Distribution Range (AMDR)Distribution Range (AMDR)

AMDR is a way to express the % of calories AMDR is a way to express the % of calories from macronutrients associated with from macronutrients associated with reduced risk of chronic diseases.reduced risk of chronic diseases.

Adults ≥19 years:Adults ≥19 years: % of daily calories% of daily calories CarbohydratesCarbohydrates 45 - 6545 - 65 FatsFats 20 - 35%(goal< or= 20 - 35%(goal< or=

30%)30%) ProteinsProteins 10 - 35%10 - 35% ≤≤25% of total calories from “refined and 25% of total calories from “refined and

processed sugars”. (goal 10%)processed sugars”. (goal 10%)

The ranges were designed to ensure that The ranges were designed to ensure that

micronutrients are sufficiently taken in the micronutrients are sufficiently taken in the

diet.diet.

Diets that are very low in either Diets that are very low in either

carbohydrates or fats are likely to be carbohydrates or fats are likely to be

deficient in one or more of the essential deficient in one or more of the essential

micronutrients .micronutrients .

Diets that are very low in protein lead to loss Diets that are very low in protein lead to loss

of lean muscle mass.of lean muscle mass.

CARBOHYDRATESCARBOHYDRATES

Classification of carbohydrates:Classification of carbohydrates: 1-Monosaccharide1-Monosaccharide e.g. glucose and e.g. glucose and

fructosefructose

2- Disaccharides2- Disaccharides e.g. sucrose, maltose and e.g. sucrose, maltose and lactoselactose

3- Polysaccharides3- Polysaccharides e.g. starch and e.g. starch and glycogenglycogen

4-Non starch polysaccharides 4-Non starch polysaccharides (Fiber)(Fiber) :components of dietary plants that :components of dietary plants that cannot be broken down by human digestive cannot be broken down by human digestive enzymes, e.g. cellulose and pectin. enzymes, e.g. cellulose and pectin.

Importance of carbohydrates:Importance of carbohydrates: A- It is the A- It is the major source of energymajor source of energy in in

most of the tissues, allowing protein to most of the tissues, allowing protein to be used for growth and maintenance be used for growth and maintenance (protein- sparing)(protein- sparing)

B- The B- The only sourceonly source of energy of energy for RBCsfor RBCs, , and is also needed for proper brain and is also needed for proper brain function.function.

C- C- A small amountA small amount is needed to is needed to prevent prevent ketosisketosis. .

D- D- Fiber hasFiber has several several beneficial effectsbeneficial effects on on health.health.

Dietary FiberDietary Fiber

Several different types.(Table-2)Several different types.(Table-2) Each has different chemical and physical Each has different chemical and physical

properties, and different effects on body properties, and different effects on body function or metabolism.function or metabolism.

Some are partially broken down by intestinal Some are partially broken down by intestinal bacteria. bacteria.

Those that have been shown to have beneficial Those that have been shown to have beneficial effects in humans are termed effects in humans are termed ffunctional fiberunctional fiber. .

Recommended intake(AI) for total fiber:Recommended intake(AI) for total fiber: : : 38 g/d for men ages 14 - 50 y; 38 g/d for men ages 14 - 50 y; 25 g/d for women ages 19 - 50 y25 g/d for women ages 19 - 50 y

Carbohydrate and blood Carbohydrate and blood glucose:glucose:

The pattern of the rise in blood The pattern of the rise in blood glucose level differs after the glucose level differs after the intake of different types of intake of different types of carbohydrate containing foods. carbohydrate containing foods.

The term The term glycemic indexglycemic index (GI)(GI) was was introduced to compare the effect introduced to compare the effect of different types of food on blood of different types of food on blood glucose.glucose.

Glycemic index (GI) is defined as:Glycemic index (GI) is defined as: “The area under the blood glucose “The area under the blood glucose curve seen after ingestion of meal curve seen after ingestion of meal with carbohydrate-rich food, with carbohydrate-rich food, compared with the area under the compared with the area under the blood glucose curve observed after a blood glucose curve observed after a meal consisting of the same amount meal consisting of the same amount of carbohydrate in the form of of carbohydrate in the form of glucose or white bread.”glucose or white bread.”

Food with low GI are useful in Food with low GI are useful in dietary management of diabetes ,and dietary management of diabetes ,and give a feeling of satiety for a longer give a feeling of satiety for a longer period (help weight control)period (help weight control)

In general, whole grains, In general, whole grains,

legumes, fruits, vegetables have legumes, fruits, vegetables have

low GI’s (lower than the same low GI’s (lower than the same

amount of white rice) amount of white rice)

Amylose form of starch has lower Amylose form of starch has lower

GI than amylopectinGI than amylopectin

It was found that the processing of It was found that the processing of

grains increase their GIgrains increase their GI

Factors Influencing GIFactors Influencing GI Not only the type and amount of Not only the type and amount of

CHO that affects the GI, it was found CHO that affects the GI, it was found

that it is affected by many other that it is affected by many other

factors including:factors including:

Nature of starchNature of starch

The presence of fat, protein, fiberThe presence of fat, protein, fiber

The way of food preparationThe way of food preparation

FATSFATS

Dietary FatsDietary Fats

Dietary fats include : triglycerides, Dietary fats include : triglycerides, phospholipids and cholesterol. phospholipids and cholesterol.

TriglyceridesTriglycerides are quantitatively the most are quantitatively the most important class of dietary fats. Their important class of dietary fats. Their biologic properties are determined by the biologic properties are determined by the chemical nature of the constituent fatty chemical nature of the constituent fatty acids , in particular, the presence or acids , in particular, the presence or absence of double bonds ,the number and absence of double bonds ,the number and location of the double bonds, and the cis- location of the double bonds, and the cis- trans configuration of the unsaturated trans configuration of the unsaturated fatty acids. fatty acids.

Importance of Dietary Importance of Dietary FatsFats

TriglyceridesTriglycerides can be utilized by many can be utilized by many tissues of the body as an energy source.tissues of the body as an energy source.

Fats Fats provide a vehicle delivering fat provide a vehicle delivering fat soluble vitamins to the body. A fat free soluble vitamins to the body. A fat free diet would lead to deficiency of these diet would lead to deficiency of these vitamins.vitamins.

FatsFats provide essential fatty acids , which provide essential fatty acids , which cannot be synthesized by the body. A cannot be synthesized by the body. A very low fat diet could lead to deficiency very low fat diet could lead to deficiency of these acids .of these acids .

Dietary cholesterol:Dietary cholesterol: cannot be used as a cannot be used as a source of energy , but is metabolized to source of energy , but is metabolized to bile salts and steroid hormones.bile salts and steroid hormones.

Dietary Fats and Plasma Dietary Fats and Plasma LipidsLipids

Saturated fat:Saturated fat: Consumption of Consumption of saturated fats is strongly associated saturated fats is strongly associated with high levels of total plasma with high levels of total plasma cholesterol and LDL cholesterol, and cholesterol and LDL cholesterol, and an increased risk of CHD. an increased risk of CHD.

The main sources of saturated fatty The main sources of saturated fatty acids are dairy and meat products and acids are dairy and meat products and some vegetable oils , such as coconut some vegetable oils , such as coconut and palm oils .It is advisable to limit and palm oils .It is advisable to limit the intake to<10% of total calories. A the intake to<10% of total calories. A goal of 7% is suggested to lower the goal of 7% is suggested to lower the risk of CHD. risk of CHD.

Dietary Fats and Plasma Dietary Fats and Plasma Lipids Lipids

( continue )( continue ) Monounsaturated fatty acids:Monounsaturated fatty acids:

Substitution of saturated fatty acids Substitution of saturated fatty acids with monounsaturated fatty acids (from with monounsaturated fatty acids (from plant sources , such as olive oil) help to plant sources , such as olive oil) help to decrease total and LDL-cholesterol , decrease total and LDL-cholesterol , without affecting the HDL-cholesterol without affecting the HDL-cholesterol or the triglycerides level . or the triglycerides level .

It is recommended that It is recommended that monounsaturated fatty acids should monounsaturated fatty acids should constitute >10 % of the total calories in constitute >10 % of the total calories in the diet. the diet.

Dietary Fats and Plasma Lipids Dietary Fats and Plasma Lipids ( continue )( continue )

Polyunsaturated fatty acids:Polyunsaturated fatty acids: they are derived from plant they are derived from plant sources and fish. An intake of 10% of total calories is sources and fish. An intake of 10% of total calories is recommended.recommended.

Their effects are influenced by the position of the double Their effects are influenced by the position of the double bonds within the molecule .bonds within the molecule .

a-n-6- (or omega-6 ) fatty acidsa-n-6- (or omega-6 ) fatty acids also seem to decrease total also seem to decrease total and LDL-cholesterol when used instead of saturated fatty and LDL-cholesterol when used instead of saturated fatty acids , but they decrease HDL-cholesterol also .However , acids , but they decrease HDL-cholesterol also .However , the benefits of lowering LDL-cholesterol is more important the benefits of lowering LDL-cholesterol is more important medically. Nuts ,avocado , olives , soybeans and various medically. Nuts ,avocado , olives , soybeans and various oils are common sources.oils are common sources.

b- n-3- ( or omega- 3 ) fatty acidsb- n-3- ( or omega- 3 ) fatty acids reduce serum reduce serum triglycerides, but have little effect on LDL or HDL triglycerides, but have little effect on LDL or HDL cholesterol level .However , they decrease the tendency to cholesterol level .However , they decrease the tendency to thrombosis , and subsequently reduce the risk of thrombosis , and subsequently reduce the risk of cardiovascular disease. Sources include plants and fish oil. cardiovascular disease. Sources include plants and fish oil.

Dietary Fats and Plasma Dietary Fats and Plasma Lipids Lipids

( continue )( continue ) Trans fatty acids:Trans fatty acids: they are the fatty acids they are the fatty acids with some of its double bonds in the trans with some of its double bonds in the trans position, they may be present in natural position, they may be present in natural food as whole milk and diary products , but food as whole milk and diary products , but mostly they are produced by partial mostly they are produced by partial hydrogenation of vegetable oil.hydrogenation of vegetable oil.

They increase LDL-cholesterol , increasing They increase LDL-cholesterol , increasing the risk of CHD. the risk of CHD.

Trans fatty acids are mainly present in Trans fatty acids are mainly present in products made from partially hydrogenated products made from partially hydrogenated oils such as baked products including oils such as baked products including crackers, cookies, doughnuts, breads, and crackers, cookies, doughnuts, breads, and products like French fries or chicken fried products like French fries or chicken fried in hydrogenated shortening. in hydrogenated shortening.

The recommended daily intake of trans The recommended daily intake of trans fatty acids should be less than 2.0 % of fatty acids should be less than 2.0 % of total calorie intake. total calorie intake.

Dietary Fats and Plasma Dietary Fats and Plasma Lipids Lipids

( continue )( continue ) Dietary cholesterol:Dietary cholesterol: It is only from animal It is only from animal

sourcessources Increased dietary cholesterol leads to Increased dietary cholesterol leads to

significant increase in total cholesterol in significant increase in total cholesterol in animal , but this is not so obvious in human.animal , but this is not so obvious in human.

An increase in dietary cholesterol in humans An increase in dietary cholesterol in humans leads to an increase in LDL-cholesterol which leads to an increase in LDL-cholesterol which differs from person to person. differs from person to person.

It is recommended to decrease the amount of It is recommended to decrease the amount of dietary cholesterol to less than 200 mg/day. dietary cholesterol to less than 200 mg/day.

Dietary Fats and Plasma Dietary Fats and Plasma Lipids Lipids

( continue )( continue ) Plant sterols:Plant sterols: Found in many plant sources Found in many plant sources

(e.g. soybean ) , and some (e.g. soybean ) , and some margarines.margarines.

Reduce plasma LDL cholesterol Reduce plasma LDL cholesterol by interfering with absorption of by interfering with absorption of dietary cholesteroldietary cholesterol

PROTEINPROTEIN

The Role and Fate Of The Role and Fate Of Dietary ProteinsDietary Proteins

--The main role of dietary protein is maintenance of The main role of dietary protein is maintenance of tissue structure ,function and integrity.tissue structure ,function and integrity.

-Some amino acids are precursors of biologically -Some amino acids are precursors of biologically active compounds, e.g. epinephrine, serotonin.active compounds, e.g. epinephrine, serotonin.

-Incase of dietary restriction dietary protein is -Incase of dietary restriction dietary protein is used as a source of energy after removal of used as a source of energy after removal of amino group and conversion into glucose or keto amino group and conversion into glucose or keto acids and fatty acids.acids and fatty acids.

-Incase of adequate supply of carbohydrates and -Incase of adequate supply of carbohydrates and fat , excess protein is stored as triglycerides in fat , excess protein is stored as triglycerides in adipose tissue.adipose tissue.

Protein Intake and Protein Intake and Nitrogen BalanceNitrogen Balance

Nitrogen balanceNitrogen balance is a comparison is a comparison between the intake of between the intake of nitrogen( mainly as protein) and nitrogen( mainly as protein) and the excretion of nitrogen (mainly in the excretion of nitrogen (mainly in the form of undigested protein in the form of undigested protein in feces and urea and ammonia in the feces and urea and ammonia in the urine).urine).

The normal healthy adult should be The normal healthy adult should be in equilibrium , with intake=losses. in equilibrium , with intake=losses.

Positive nitrogen balancePositive nitrogen balance occurs in occurs in significant degree during child significant degree during child development, during pregnancy and in a development, during pregnancy and in a convalescing adult when there is convalescing adult when there is accumulation of proteins in the body. accumulation of proteins in the body.

Negative nitrogen balanceNegative nitrogen balance occurs when : occurs when :

(1) dietary intake is insufficient ,or (1) dietary intake is insufficient ,or

(2) one of the essential amino acids is (2) one of the essential amino acids is deficient or lacking in the diet. deficient or lacking in the diet.

Negative nitrogen balance can occur Negative nitrogen balance can occur when the body is under stress condition when the body is under stress condition as in cases of burn, injury, sepsis or as in cases of burn, injury, sepsis or cancer , where there is increased cancer , where there is increased amount of nitrogen excretion.amount of nitrogen excretion.

In other words:In other words:

Positive Nitrogen Positive Nitrogen BalanceBalance

Negative Nitrogen Negative Nitrogen BalanceBalance

1. Stress

2. Decreased Intake

3. Lack of an essential AA

Requirements and Requirements and Adequacy of Dietary Adequacy of Dietary

ProteinsProteins --A certain amount of protein is needed A certain amount of protein is needed

daily in the diet as it cannot be stored in daily in the diet as it cannot be stored in the body.the body.

-Proteins from different sources differ in -Proteins from different sources differ in their composition and content of the their composition and content of the essential amino acids, hence they are not essential amino acids, hence they are not equally useful as building blocks for equally useful as building blocks for proteins in our body.proteins in our body.

-The usefulness of the protein is expressed -The usefulness of the protein is expressed in terms of either net protein utilization in terms of either net protein utilization (NPU) or biological value (BV). (NPU) or biological value (BV).

Requirement and Adequacy Requirement and Adequacy of Dietary Proteins of Dietary Proteins (continue)(continue)

NPUNPU= = NN retainedretained X 100 X 100

== NN intake – intake – NN output output X 100 X 100

BVBV= = NN retained retained X 100 X 100

N intake

N intake

N absorbed

Protein QualityProtein Quality

Proteins with high BV or NPU are Proteins with high BV or NPU are of higher quality.of higher quality.

NPU of dietary proteins varies NPU of dietary proteins varies according to source .according to source .

Proteins from animal sources are Proteins from animal sources are of higher quality, e.g. albumin of higher quality, e.g. albumin NPU=91%, beef NPU=67%.NPU=91%, beef NPU=67%.

Vegetable proteins have lower Vegetable proteins have lower quality, NPU for gluten= 42%quality, NPU for gluten= 42%

Recommended Dietary Recommended Dietary AllowanceAllowance

Assuming adequate calorie intake Assuming adequate calorie intake and 75% efficiency of utilization , and 75% efficiency of utilization , which is typical of the mixed protein which is typical of the mixed protein in the average diet , the in the average diet , the recommended protein intake is 0.8 g recommended protein intake is 0.8 g / kg body wt/day./ kg body wt/day.

This should be increased on a This should be increased on a vegetarian diet with lower efficiency.vegetarian diet with lower efficiency.

Protein requirements are increased Protein requirements are increased during growth and recovery during growth and recovery following an illness (table 3) following an illness (table 3)

Vegetarian Diet and Vegetarian Diet and Adequate Adequate

Protein IntakeProtein Intake Vegetable proteins are often low in one or more essential amino Vegetable proteins are often low in one or more essential amino

acids , for example legumes contain low amount of Met, while acids , for example legumes contain low amount of Met, while

grains are low in Lys.grains are low in Lys.

Therefore, to provide an adequate vegetarian diet that contains Therefore, to provide an adequate vegetarian diet that contains

all of the required amino acids , two or more proteins must be all of the required amino acids , two or more proteins must be

consumed together to complement one another in the missing consumed together to complement one another in the missing

amino acids . For example, beans which contain low amount of amino acids . For example, beans which contain low amount of

Met but rich in Lys , should be eaten with corn , which is low in Met but rich in Lys , should be eaten with corn , which is low in

Lys .(Mexican food)Lys .(Mexican food)

The low amino acid is termed the The low amino acid is termed the limiting amino acidlimiting amino acid