Transcript sources of energy :macronutrient

SOURCES OF ENERGY
:MACRONUTRIENT
- Macronutrients include:
 Carbohydrates.
 Fats.
 Proteins.
- Carbohydrates and Fats are the principal
energy sources.
- Dietary proteins serve many roles including
energy production.
FACTORS EFFECTING ENERGY
EXPENDITURE
- There are four principal factors that affect individual
energy expenditure:
 Surface area (which is related to height and weight)
 Age (reflects growth and lean muscle mass)
 Sex (women have a lower BMR due to lower % of
lean muscle mass and the effects of female
hormones on metabolism).
 Activity level :The long term effect is more
important than the immediate one .It leads to an
increase in lean muscle mass and hence BMR.
EFFECT OF BODY COMPOSITION
ON BMR
Acceptable Macronutrient Distribution
Range (AMDR)

AMDR is a way to express the % of calories from
macronutrients associated with reduced risk of chronic
diseases.
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Adults ≥19 years:
% of daily calories
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Carbohydrates
45 - 65
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Fats
20 - 35%(goal< or= 30%)

Proteins
10 - 35%

≤25% of total calories from “refined and processed
sugars”. (goal 10%)

The ranges were designed to ensure that
micronutrients are sufficiently taken in the diet.

Diets that are very low in either carbohydrates
or fats are likely to be deficient in one or more
of the essential micronutrients .

Diets that are very low in protein lead to loss of
lean muscle mass.
CARBOHYDRATES

Classification of carbohydrates:
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1-Monosaccharide e.g. glucose and fructose
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2- Disaccharides e.g. sucrose, maltose and lactose
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3- Polysaccharides e.g. starch and glycogen

4-Non starch polysaccharides (Fiber) :components
of dietary plants that cannot be broken down by
human digestive enzymes, e.g. cellulose and
pectin.
 Importance
of carbohydrates:

A- It is the major source of energy in most of the
tissues, allowing protein to be used for growth and
maintenance (protein- sparing)

B- The only source of energy for RBCs, and is also
needed for proper brain function.

C- A small amount is needed to prevent ketosis.

D- Fiber has several beneficial effects on health.
Dietary Fiber

Several different types.(Table-2)

Each has different chemical and physical properties,
and different effects on body function or metabolism.

Some are partially broken down by intestinal bacteria.
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Those that have been shown to have beneficial effects
in humans are termed functional fiber.

Recommended intake(AI) for total fiber: :

38 g/d for men ages 14 - 50 y;

25 g/d for women ages 19 - 50 y
Carbohydrate and blood glucose:
The pattern of the rise in blood glucose
level differs after the intake of different
types of carbohydrate containing foods.
 The
term glycemic index (GI) was
introduced to compare the effect of different
types of food on blood glucose.


Glycemic index (GI) is defined as: “The area
under the blood glucose curve seen after
ingestion of meal with carbohydrate-rich
food, compared with the area under the
blood glucose curve observed after a meal
consisting of the same amount of
carbohydrate in the form of glucose or white
bread.”
 Food with low GI are useful in dietary
management of diabetes ,and give a feeling
of satiety for a longer period (help weight
control)

In general,
whole grains, legumes, fruits,
vegetables have low GI’s (lower than the same
amount of white rice)

Amylose form of starch has lower GI than
amylopectin

It was found that the processing of grains
increase their GI
Factors Influencing GI
Not only the type and amount of CHO that
affects the GI, it was found that it is affected by
many other factors including:

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Nature of starch
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The presence of fat, protein, fiber
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The way of food preparation
FATS
Dietary Fats

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Dietary fats include : triglycerides, phospholipids
and cholesterol.
Triglycerides are quantitatively the most important
class of dietary fats. Their biologic properties are
determined by the chemical nature of the
constituent fatty acids , in particular, the presence
or absence of double bonds ,the number and
location of the double bonds, and the cis- trans
configuration of the unsaturated fatty acids.
Importance of Dietary Fats

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Triglycerides can be utilized by many tissues of
the body as an energy source.
Fats provide a vehicle delivering fat soluble
vitamins to the body. A fat free diet would lead to
deficiency of these vitamins.
Fats provide essential fatty acids , which cannot be
synthesized by the body. A very low fat diet could
lead to deficiency of these acids .
Dietary cholesterol: cannot be used as a source of
energy , but is metabolized to bile salts and
steroid hormones.
Dietary Fats and Plasma Lipids

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Saturated fat: Consumption of saturated fats
is strongly associated with high levels of
total plasma cholesterol and LDL
cholesterol, and an increased risk of CHD.
The main sources of saturated fatty acids
are dairy and meat products and some
vegetable oils , such as coconut and palm
oils .It is advisable to limit the intake
to<10% of total calories. A goal of 7% is
suggested to lower the risk of CHD.
Dietary Fats and Plasma Lipids
( continue )

Monounsaturated fatty acids: Substitution
of saturated fatty acids with
monounsaturated fatty acids (from plant
sources , such as olive oil) help to decrease
total and LDL-cholesterol , without affecting
the HDL-cholesterol or the triglycerides
level .

It is recommended that monounsaturated
fatty acids should constitute >10 % of the
total calories in the diet.
Dietary Fats and Plasma Lipids ( continue )

Polyunsaturated fatty acids: they are derived from plant sources
and fish. An intake of 10% of total calories is recommended.

Their effects are influenced by the position of the double bonds
within the molecule .
a-n-6- (or omega-6 ) fatty acids also seem to decrease total and LDLcholesterol when used instead of saturated fatty acids , but they
decrease HDL-cholesterol also .However , the benefits of lowering
LDL-cholesterol is more important medically. Nuts ,avocado ,
olives , soybeans and various oils are common sources.
b- n-3- ( or omega- 3 ) fatty acids reduce serum triglycerides, but
have little effect on LDL or HDL cholesterol level .However , they
decrease the tendency to thrombosis , and subsequently reduce
the risk of cardiovascular disease. Sources include plants and fish
oil.
Dietary Fats and Plasma Lipids
( continue )
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Trans fatty acids: they are the fatty acids with some
of its double bonds in the trans position, they may
be present in natural food as whole milk and diary
products , but mostly they are produced by partial
hydrogenation of vegetable oil.
They increase LDL-cholesterol , increasing the
risk of CHD.
Trans fatty acids are mainly present in products
made from partially hydrogenated oils such as
baked products including crackers, cookies,
doughnuts, breads, and products like French fries
or chicken fried in hydrogenated shortening.
The recommended daily intake of trans fatty acids
should be less than 2.0 % of total calorie intake.
Dietary Fats and Plasma Lipids
( continue )

Dietary cholesterol: It is only from animal sources

Increased dietary cholesterol leads to significant
increase in total cholesterol in animal , but this is
not so obvious in human.

An increase in dietary cholesterol in humans leads
to an increase in LDL-cholesterol which differs
from person to person.

It is recommended to decrease the amount of
dietary cholesterol to less than 200 mg/day.
Dietary Fats and Plasma Lipids
( continue )

Plant sterols:

Found in many plant sources (e.g. soybean )
, and some margarines.
Reduce plasma LDL cholesterol by
interfering with absorption of dietary
cholesterol
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PROTEIN
The Role and Fate Of Dietary
Proteins
-The main role of dietary protein is maintenance of tissue
structure ,function and integrity.
-Some amino acids are precursors of biologically active
compounds, e.g. epinephrine, serotonin.
-Incase of dietary restriction dietary protein is used as a
source of energy after removal of amino group and
conversion into glucose or keto acids and fatty acids.
-Incase of adequate supply of carbohydrates and fat ,
excess protein is stored as triglycerides in adipose tissue.
Protein Intake and Nitrogen Balance

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Nitrogen balance is a comparison between
the intake of nitrogen( mainly as protein)
and the excretion of nitrogen (mainly in the
form of undigested protein in feces and urea
and ammonia in the urine).
The normal healthy adult should be in
equilibrium , with intake=losses.
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Positive nitrogen balance occurs in significant
degree during child development, during
pregnancy and in a convalescing adult when
there is accumulation of proteins in the body.
Negative nitrogen balance occurs when :
(1) dietary intake is insufficient ,or
(2) one of the essential amino acids is
deficient or lacking in the diet.
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Negative nitrogen balance can occur when
the body is under stress condition as in cases
of burn, injury, sepsis or cancer , where there
is increased amount of nitrogen excretion.
In other words:
Positive Nitrogen Balance
Negative Nitrogen Balance
1. Stress
2. Decreased Intake
3. Lack of an essential AA
Requirements and Adequacy of
Dietary Proteins
-A certain amount of protein is needed daily in
the diet as it cannot be stored in the body.
-Proteins from different sources differ in their
composition and content of the essential
amino acids, hence they are not equally useful
as building blocks for proteins in our body.
-The usefulness of the protein is expressed in
terms of either net protein utilization (NPU)
or biological value (BV).
Requirement and Adequacy of
Dietary Proteins (continue)

NPU= N retained X 100
N intake
= N intake – N output X 100
N intake

BV= N retained
N absorbed
X 100
Protein Quality
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Proteins with high BV or NPU are of higher
quality.
NPU of dietary proteins varies according to
source .
Proteins from animal sources are of higher
quality, e.g. albumin NPU=91%, beef
NPU=67%.
Vegetable proteins have lower quality, NPU
for gluten= 42%
Recommended Dietary Allowance

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Assuming adequate calorie intake and 75%
efficiency of utilization , which is typical of
the mixed protein in the average diet , the
recommended protein intake is 0.8 g / kg
body wt/day.
This should be increased on a vegetarian
diet with lower efficiency.
Protein requirements are increased during
growth and recovery following an illness
(table 3)
Vegetarian Diet and Adequate
Protein Intake

Vegetable proteins are often low in one or more essential amino
acids , for example legumes contain low amount of Met, while
grains are low in Lys.

Therefore, to provide an adequate vegetarian diet that contains
all of the required amino acids , two or more proteins must be
consumed together to complement one another in the missing
amino acids . For example, beans which contain low amount of
Met but rich in Lys , should be eaten with corn , which is low in
Lys .(Mexican food)

The low amino acid is termed the limiting amino acid