BCH 301: NUTRITIONAL BIOCHEMISTRY

Nutrition is the sum of all processes involved in the intake, assimilation, and utilization of the
proper amounts of nutrients to maintain health, well-being, and productivity. Good nutrition
relies on a diverse, adequate diet and is essential for the development and maintenance of the
body from infancy to old age. Nutritional status can be both the “cause” and the “outcome” of
good or poor health.
The terms “nutrition” and “food” are closely related but not interchangeable. Nutrition is a
process of events, while food is a product that is eaten or taken into the body.

Food is essential because it contains nutrients that the body needs for:

• Developing, growing, maintaining, replacing, and repairing cells and tissues

• Resisting and fighting infection and recovering from illness
• Producing energy, warmth, movement, and work
• Carrying out chemical processes such as digestion

Nutrients are the substances in food that the body uses to function properly. Nutrients are
divided into macronutrients and micronutrients.

Macronutrients are nutrients needed by the body in relatively large quantities (many grams per
day). They are carbohydrates, fats, and proteins.

Micronutrients are nutrients needed by the body in very small quantities (usually less than 1
gram per day). They are vitamins and minerals.
The body ingests, assimilates, and utilizes the nutrients in food to meet its needs for
macronutrients and micronutrients.
The body’s physical and chemical process of breaking down food and converting it into a useful
form of energy is called metabolism.
The energy produced by metabolism is essential to maintain the body’s functions and daily
activities.
The ability to metabolize food may vary from person to person and may be affected by illness or
disease.
Balancing the body’s ability to metabolize food with an appropriate quantity of nutrients and
food types will help ensure good health.
The body responds either positively or negatively when it absorbs a nutrient or group of
nutrients. The response affects the body’s condition and health status. The body’s response to
nutrients and the subsequent outcome is called nutritional status.
Eating a variety of foods is key to good health, especially for people with special needs, such as
infants, young children, pregnant and lactating women, and the elderly.
Eating a wide assortment of foods increases the likelihood of getting the necessary nutrients.
Except for breastmilk, no single food provides all the nutrients the body needs to function
properly.

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THE ESSENTIAL NUTRIENT GROUPS

To function properly, the body must maintain a proper balance of the following key nutrients:

• Carbohydrates
• Proteins
• Fats
• Vitamins
• Minerals
• Water

CARBOHYDRATES

Carbohydrates are called energy-giving foods because they make up a large percentage of the
energy in people’s diets.
In developing countries the basic foods that people eat regularly (staple foods) are usually high
in carbohydrates.
In fact, carbohydrates account for up to 80 percent of the total energy in diets in developing
countries, compared with 45–50 percent in industrialized countries.
Staple foods often contain other essential nutrients such as protein, vitamins, and minerals, but in
smaller amounts. Staple foods are usually produced locally and are readily available, accessible,
and affordable.
Rich sources of carbohydrates include cereals (rice, millet, sorghum, wheat, and barley), root
crops (cassava, sweet potatoes, yams, and potatoes), and starchy fruits (green bananas and
plantains). These foods contain what are known as complex carbohydrates. Complex
carbohydrates usually provide more fiber, vitamins, and minerals than simple carbohydrates.
Simple carbohydrates provide energy but are often called “empty calories” because they lack the
extra vitamins and minerals found in complex carbohydrates. Simple carbohydrates are quickly
digested and absorbed because they lack fiber. They include sugar, honey, and baked goods such
as doughnuts and cake.
Carbohydrates cannot meet all the body’s energy needs because they do not provide all the
essential nutrients. People should eat other kinds of food in combination with staple foods for a
nutritious and well-balanced diet.
The digestible carbohydrates are the major sources of food energy, yielding 4 kcal/g and
provides about 60 to 70% of the energy requirement. In addition, these carbohydrates have
protein sparing effect.
Dietary Carbohydrates can be available carbohydrate or unavailable carbohydrate

i. Available carbohydrates: These can be metabolized by the body to give energy

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The major dietary polysaccharide is starch. It is digested by amylase to maltose and then
hydrolysed to glucose. This glucose is the major source of fuel for most organs and tissues.
Excess glucose is converted to fat and stored. It can also be converted to glycogen for storage.
On cooking starch is made more soluble and accessible to digestive enzymes. Cereals, pulses and
tubers are the major sources of starch in the diet. Germination of legumes leads to partial
breaking down of the starch present in them. Carbohydrates contents in common foods are
shown below
1. Cane sugar 100%
2. Cassava 85%
3. Rice 80%
4. Honey 80%
5. Wheat 70-80%
6. Cakes 55-65%
7. Bread 50-60%
8. Potatoes 25%

Sucrose
Cane sugar is mainly used as a sweetening agent. In young children high intake of sucrose and
sucrose-rich food items predispose them to the development of dental caries.
Sucrose is easily fermented by the bacteria present in dental plaque, which would damage the
enamel and lead to caries (tooth decay).
In adults, consumption of large quantities of refined sugars is not advisable since they tend to
produce a sudden rise in blood glucose levels. This will also lead to excessive calorie intake.
Sucrose consumption also results in increased levels of plasma lipids. While prescribing diets for
diabetic patients and for weight reduction, sucrose should be strictly avoided. Jaggery, an
alternative source of sucrose is beneficial, since it is a good source of iron.

ii. Unavailable carbohydrates: These cannot be assimilated and constitute only the dietary
fiber. Unavailable or indigestible carbohydrate in the diet is called dietary fiber.
Dietary fiber is necessary to maintain the normal motility of gastrointestinal tract. The dietary
fiber is not digested by the enzyme of the human gastrointestinal tract, where most of the other
carbohydrates like starch, sugars are digested and absorbed.
Plant foods are the only sources of dietary fiber. It is found in vegetables, fruits, and grains. Diet
rich in fiber improves bowel motility, prevents constipation, decreases reabsorption of bile acids

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thus lowering cholesterol level and improves glucose tolerance. The beneficial effect is more
with soluble fiber present in vegetables and only a diet having plenty of vegetables and green
leaves will have the desired effect.
Fiber requirement is about 30 g/day. The inclusion of fiber rich food in weight reducing diets is
found to be helpful, since it provides a feeling of fullness without consumption of excess
calories.
Importance of fiber
Water holding capacity: The dietary fibers have a property of holding water and swell like
sponge with a concomitant increase in viscosity. Thus, fiber adds bulk to the diet and increases
transit time in the gut (gastric emptying time) due to high viscosity.
Adsorption of organic molecules: The organic molecules like bile acids, neutral sterols,
carcinogens, and toxic compounds can be adsorbed on dietary fiber and facilitates its excretion.
It increases stool bulk: The fiber absorbs water and increases the bulk of the stool and helps to
reduce the tendency towards constipation by increasing bowel movements.
Hypoglycemic effect of fiber: It is effective in reducing blood sugar.
Hypocholesterolemic effects of fiber: Fiber has cholesterol lowering effect. Fiber binds bile
acids and cholesterol, increasing their fecal exertion and thus decreasing plasma and tissue
cholesterol level.
High fiber diet is associated with reduced incidence of a number of diseases like Coronary heart
disease (CHD), Colon cancer, Diabetes, Diverticulosis, Hemorrhoids (piles).

Adverse effect of dietary fiber

Dietary fiber also have some adverse effects on nutrition by binding some mineral elements and
preventing their proper absorption. Thus, high dietary fiber intake may lead to deficiency of
mineral elements.

LIPIDS

Lipids are found in fats and oils and are a concentrated source of high energy that is slowly
absorbed by the body. Lipids provide essential fatty acids that the body does not produce itself
and has to get from food. In developing countries lipids represent only 8 percent of the total
energy in people’s diets, compared with as much as 36 percent in high-income countries.
Foods that contain lipids generally have a satisfying taste, ensuring that people include them in
their diets.
These foods include butter, margarine, and lard, which are solid at room temperature, and corn
oil, olive oil, cotton oil, linseed oil, and soybean oil, which are liquid at room temperature.
Lipids are categorized as visible and invisible fats.
Visible fats are easily recognized and include butter, margarine, vegetable oils, bacon fat, and
lard. Their lipid content can be measured accurately. Recommended daily intake of visible fat is
10% of calories or 20 g/day; in pregnancy 30 g/day and during lactation 45 g/day.
Invisible fats are not seen or measured as easily and are found in milk, nuts, avocados, cheese,
egg yolks, fish, meat, cereals, oil seeds and baked goods such as cake. More than half of essential
fatty acid in diet is in the form of invisible fat.

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The body digests and absorbs liquids more slowly than carbohydrates and proteins. Lipids leave
people feeling satisfied longer and provide nearly twice as much energy as other macronutrients.
Because they are energy dense, lipids are important for people who need to gain weight.
Because dietary lipids also help the body transport and absorb fat-soluble vitamins, they may be
a good source of vitamins A, D, E, and K.
However, eating too many lipids may lead to heart disease, obesity, and related complications.
People should therefore eat lipids sparingly.
Lipids provide a concentrated source of energy. In developed countries, the percentage of
calories derived from fats may be as high as 40%, but in the developing countries it is much less,
around 10%.
Lipids yield 9 kcal/g.
Besides satisfying metabolic energy needs, there are two essential functions of dietary fat,
namely, to provide:
1. A vehicle for the absorption of the fat soluble vitamins (A, D, E and K).
2. To supply essential fatty acids, linoleic acid and linolenic acid to the body and provide
energy.
A minimum intake of lipids is therefore essential since the requirements of fat soluble vitamins
and essential fatty acids are to be met.
Fats increase the taste and palatability of food.

Cholesterol and Heart Diseases

The atherogenic effect of cholesterol and the risk of coronary artery disease in people with
hypercholesterolemia are well known. Hence it is always advisable that, dietary intake should be
restricted.
Food items known to be rich in cholesterol (egg yolk, liver, brain, kidney) are to be consumed in
limited amounts.
Vegetables, cereals and pulses do not contain any cholesterol. On the other hand, vegetable
sterols will inhibit cholesterol absorption.
Saturated fats raise serum cholesterol; while unsaturated fats lower it. Therefore, unsaturated fat
(vegetable oils and fish oils) are to be preferred.
Food item Cholesterol content (mg/100 gm)
Hen’s egg (whole) 300
Egg yolk 1330
Liver 300-600
Brain 2000
Butter 280
Meat and fish 40-200
Milk 10
The polyunsaturated fatty acids (PUFA) are present in vegetable oils and fish oils. They are
essential fatty acids and precursors of prostaglandins and leukotrienes. PUFAs are required for
esterification and excretion of cholesterol. They reduce the cholesterol level in blood and are
antiatherogenic. The omega-3 fatty acids from fish oils decrease the plasma lipoproteins
(VLDL and LDL) and thereby decrease the risk of coronary artery disease. High fiber content
also reduces serum cholesterol, lowers LDL fraction and raises HDL fraction.
Sources of PUFA

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Name Carbon atoms omega family number of bonds Sources
Linoleic acid 18 w6 2 Vegetable oil
Linolenic acid 18 w3 3 Vegetable oil
Arachidonic 20 w6 4 Vegetable oil
Timnodonic 20 w3 5 Fish oils

Fat or oil Saturated (%) Mono unsaturated (%) Polyunsaturated (%)

Butter/ghee 75 20 5
Safflower oil 9 12 79
Cotton seed oil 26 19 65
Coconut oil 86 12 2
Ground nut oil 18 46 36

Recommended Daily Intake of Fat

The ideal fat intake is about 15-20% of total calories, out of which about 25-30% may be PUFA.
This will be a total of about 20-25 g of oils and about 3 g of PUFA for a normal person.

Excess of PUFA: Anything in excess is deleterious. Excess PUFA may lead to production of
free radicals that may be injurious to the cell. PUFA should not be more than 30% of total fat.
Moreover, the fat content should be such that saturated fatty acid (SFA) : mono unsaturated fatty
acid (MUFA) : poly unsaturated fatty acid (PUFA) may be in 1:1:1 ratio. Further, cholesterol
intake should be less than 250 mg/day.

PROTEINS

Known as body-building foods, proteins form the main structural components of cells and, apart
from water, make up the bulk of tissues and organs. The body needs additional protein from the
diet to grow, develop, maintain, and repair tissues and muscles. Proteins are necessary for the
following:
 Growth and development
 Maintenance and repair of tissues and replacement of worn-out or damaged tissues
 Production of metabolic and digestive enzymes
 Make up of certain hormones and all cells and tissues

There are two main types of protein: plant protein, which includes legumes (e.g., beans, lentils,
soybeans, and chickpeas), groundnuts, and other nuts and
2) Animal protein, which includes meat, poultry, fish, insects, milk, cheese, and eggs.

Proteins are made of amino acids, some of which are absolutely essential for humans. Not all
proteins have the same quality and nutritional importance. Proteins in some foods do not contain
the full range of essential amino acids that the body needs.
Foods such as milk and eggs contain high-quality, easily digested proteins with the essential
amino acids. Foods such as maize and wheat contain protein with fewer essential amino acids
and are less easily digested.

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Animal protein is often of high quality and as a result contains more of the amino acids needed
for the body’s proper functioning. When people do not eat enough protein, their bodies use
protein from their muscle mass, leading to muscle wasting over time.
IMPORTANCE OF PROTEINS
Proteins form the building blocks for body tissues. Only 15-20% of the total energy is derived
from proteins. When enough carbohydrates are present in the diet, the amino acids are not used
for yielding energy. This is known as the protein sparing effect of carbohydrates. During
starvation, amino acids may act as energy sources. Proteins are the only source of essential
amino acid.
CLASSIFICATION OF AMINO ACIDS BASED ON NUTRITIONAL REQUIREMENTS
Essential or Indispensable
These include Isoleucine, Leucine, Threonine, Lysine, Methionine, Phenylalanine,
Tryptophan, and Valine. Their carbon skeleton cannot be synthesized by human beings and so
preformed amino acids are to be taken in food for normal growth.
Partially essential or Semi-essential
Histidine and arginine are semi-indispensable amino acids. Growing children require them in
food. But they are not essential for the adult individual.
Non-essential or Dispensable
The remaining 10 amino acids are non-essential, because their carbon skeleton can be
synthesized by the body. However, they are also required for normal protein synthesis.They are
Glycine, Alanine, Proline • Tyrosine, Serine, Cysteine, Glutamic acid, Aspartic acid,
Glutamine and Aspargine. All body proteins do contain all the non-essential amino acids.
For the synthesis of body proteins, all the essential amino acids should be supplied in adequate
quantities at the same time.
Cysteine and tyrosine can be synthesized, when methionine and phenyl alanine are available;
thus requirement of the precursor amino acid is determined by the availability of the product.
The remaining amino acids can be synthesized, provided there is enough supply of proteins in
total. Only 3 amino acids (alanine, aspartate and glutamate) are truly dispensable, as they can be
synthesized from pyruvate, oxaloacetate and alpha ketoglutarate respectively; and these
precursors are generally available in plenty.

NUTRITIONAL VALUES (NUTRITIONAL INDICES) OF PROTEINS

In judging the adequacy of dietary proteins to meet the human needs, not only the
quantity but the nutritional quality of the dietary proteins also matters. Proteins in different foods
vary in their nutritional quality because of the differences in their amino acid composition. The
quality of protein depends on the pattern of essential amino acids it supplies.
The best quality protein is the one which provides essential amino acid pattern very close
to the pattern of the tissue proteins. Egg proteins, human milk protein, satisfy these criteria and
are classified as high quality proteins and serve as reference protein for defining the quality of
other proteins.The modern, easier way, to assess the nutritional value of a protein, is to give that
protein as the only source of nitrogen to an animal, and assess the weight gain.
The quality of a protein is assessed by comparison to the “reference protein”, which is
usually egg protein. Four methods of assessment of protein quality are:
1. Chemical score or amino acid score
2. Net protein utilization (NPU)

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3. Protein efficiency ratio (PER)
4. Biological value (BV).

Limiting Amino Acids

Certain proteins are deficient in one or more essential amino acids. If this particular protein is fed
to a young rat as the only source of protein, it fails to grow. This amino acid is said to be the
limiting amino acid. Limiting amino acid is that which limits the weight gain when a protein is
supplied to an animal
This problem may be overcome by taking a mixture of proteins in the diet. Mutual
supplementation of proteins is thus achieved.
Animal proteins are of higher biological value than proteins from plant foods. Plant
proteins are of poorer quality since essential amino acids (EAAs) composition is not well
balanced and a few EAAs deviate much from the optimal level present in egg, e.g.
– In comparison with egg protein, cereal proteins are poor in amino acid lysine. Pulses and oil
seed proteins are rich in lysine but they are poor in sulfur containing amino acids. Such proteins
individually are therefore incomplete proteins.
However, relative insufficiency of a particular amino acid of any vegetable food can be
overcome by judicious combination with other vegetable foods, which may have adequate level
of that limiting (deficient) amino acid. The amino acid composition of these proteins
complement each other and the resulting mixture will have an amino acid pattern better than
either of the constituent proteins of the mixture. This is the procedure normally used to improve
quality of vegetable proteins. This phenomenon is called mutual supplementation effect of
amino acid. Thus, a protein of cereals, deficient in lysine but rich in methionine and pulses with
adequate lysine but deficient in methionine content have a mutually supplementary effect, a
deficiency of an amino acid in one can be made good by an adequate level in another, if both are
consumed together. Therefore, a combination of pulses plus cereal will cancel each other's
deficiency and become equivalent to first class protein. The supplementation effect of proteins
may
be seen in weight gain in animals.
Protein source limiting amono acids Protein supplemented to rectify
deficiency
Rice Lys, Thr Pulse proteins
Wheat Lys, Thr Pulse proteins
Gelatin Tryptophan Milk proteins
Zein Trp, Lys Meat proteins
Tapioca Phe, Tyr Fish proteins

Protein requirements
Protein is essential for body growth and maintenance, particularly for children and adolescents.
Because protein in the body is constantly depleted and cannot be stored, it must be replenished
daily. Requirements may differ from person to person based on health status and physiological
condition. Protein requirements for adults are the same for both sexes at all ages and body
weights, except for pregnant and lactating women.
Pregnancy substantially increases protein requirements for women to support the growth of the
fetus, placenta, and additional maternal tissue. There is some evidence that pregnant women
utilize protein less efficiently, thereby increasing the need for dietary sources.

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Lactation also increases protein needs, because breast milk must supply protein to the infant for
growth.

Table below shows the basic minimum protein required by adults to compensate for protein loss
and support growth.
Safe protein intake requirements for adults

Estimating protein requirements for infants, children, and adolescents

The first year of life is a period of rapid growth. Infants who are breastfed exclusively for the
first 6 months of life have their protein requirements met, but it is important to understand the
amount of protein needed in their diet. During the first month of life, infants need 2.5 grams of
protein per kilogram of body weight. After 4 months and up to 12 months, they need
approximately 1.5 grams per kilogram of body weight.
Protein needs often fluctuate with child growth and development. The most accurate reflection of
the protein requirements of an individual child is based on actual body weight. This calculation
involves multiplying the safe level of protein intake per age group by weight in kilograms.
Up to age 12, boys and girls need the same level of protein, but the safe protein intake level
differs slightly after that point.

Illness, intense physical activity, and starvation require special protein intake for adults and
children because the body needs additional protein to build, repair, or sustain tissues.

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Safe protein intake requirements for adults

VITAMINS

Vitamins are organic compounds that perform specific metabolic functions in the body. The
body does not synthesize most vitamins and must get them from food.
Unlike carbohydrates, lipids, and proteins, vitamins do not produce energy. However, they are
necessary for many of the metabolic processes that produce energy. People who do not eat the
proper amounts of vitamins can get vitamin deficiencies that cause illness and disease.
Vitamins are classified into two categories based on the substances they dissolve in.
Fat-soluble vitamins can be stored by the body when they are not used. These vitamins are
essential for good health but not needed every day. Fat-soluble vitamins include A, D, E, and K.
These vitamins are necessary for the development and maintenance of certain body tissues,
including those in the eyes (vitamin A), bones (vitamin D), and muscles; for the coagulation of
blood (vitamin K); for synthesizing certain enzymes, and for absorbing other essential nutrients
such as calcium (vitamin D).
Water-soluble vitamins pass directly into the bloodstream. The body has limited ability to store
these vitamins and must get them daily from food. Water-soluble vitamins include C (ascorbic

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acid), B1 (thiamine), B2 (riboflavin), B3 (niacin), B6 (pyroxidine), B12 (cobalamin), pantothenic
acid, and folic acid.
Water-soluble vitamins are often classified by their functions. Energy-releasing vitamins that
enable the body to use macronutrients include B1 (thiamine), B2 (riboflavin), B3 (niacin or
nicotinic acid), biotin, and pantothenic acid. Hematopoietic (red blood cell-synthesizing)
vitamins that help the body make new red blood cells include folacin (folic acid) and B12
(cobalamin). Co-enzyme vitamins that help the body break down amino acids, produce
enzymes, and synthesize new proteins include B6 (pyroxidine), which helps metabolize protein,
and others. Skin- and bone-building vitamins that help form collagen, an important component
of skin, bone, and connective tissues include C (ascorbic acid).

MINERALS
Minerals are inorganic compounds that are not produced by the body but are necessary for health
and well-being. Minerals are referred to as essential trace elements because they are needed in
very small quantities. While they are chemically different from, vitamins, minerals serve similar
purposes. They influence many of the body’s biochemical reactions and are used to form cells
and tissues.
Important minerals for health include iron, zinc, calcium, and iodine. Iron is an essential
component of blood and helps transfer oxygen to various tissues. Zinc is important to enhance
and strengthen the immune system, help wounds heal, and facilitate digestion and is an important
component of the skeletal system. Calcium is a key component of bone and is needed for a
strong skeleton. Other minerals involved in various body reactions are chromium, copper,
fluoride, magnesium, manganese, molybdenum, nickel, phosphorus, and selenium

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MICRONUTRIENT DEFICIENCIES

Nutritional anemia

Anemia is a disorder of the blood resulting from low hemoglobin levels in the body. Hemoglobin
is an iron-rich protein that plays a critical role in transporting oxygen throughout the body and,
when impaired, can keep key organs from functioning properly. In an anemic person, the
necessary oxygen is not circulated and used by the body, often leaving the person easily fatigued
or weak, with breathing or heart problems and experiencing dizziness or fainting. A person with
severe anemia may also have edema.

The people most affected by anemia are premature infants and children under 5. Children are
often anemic because they do not consume enough iron, which is needed to form hemoglobin.
Women of childbearing age, especially pregnant and lactating women, are especially vulnerable
to anemia because of the extra iron demands for the developing fetus.

Anemia is classified as hemorrhagic, hemolytic, hypoplastic/aplastic, and nutritional. Nutritional

anemia is the most common, caused by a deficiency of one or more essential nutrients needed to
synthesize red blood cells, such as iron, folic acid, and vitamin B12. These deficiencies cause the
following types of nutritional anemia:

• Iron deficiency anemia (the most common type)

• Folic acid deficiency anemia
• Vitamin B12 deficiency anemia

Detecting anemia

Anemia is diagnosed by measuring the hemoglobin level in the blood. People with hemoglobin
levels below the expected value for their age group are considered anemic. Measuring

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hemoglobin requires laboratory tests that are rare at community health centers. Nevertheless, it is
important to be able to recognize the cutoffs used to diagnose anemia, shown in table 11.

Table 11. Suggested cutoffs for diagnosing anemia using hemoglobin (Hb)

Effects of anemia
The main effects of anemia are listed below.
1. Reduced work capacity leading to low productivity
2. Reduced mental capacity that negatively affects school performance in children
3. Reduced immune competence leading to high incidence of disease
4. Poor pregnancy outcomes (low birth weight, spontaneous abortion, premature delivery)
5. Maternal death during pregnancy and delivery (heavy blood loss during delivery puts
mothers at risk)

Strategies to prevent and control anemia

The following interventions can help to prevent and control anemia:
1. Consumption of iron- and vitamin-rich foods.
2. Prevent and treat anemia-related diseases such as malaria.
3. Prevent and treat parasites such as hookworm to prevent anemia in children.
4. Provide iron and folic acid supplementation for high risk groups such as children,
pregnant women, and people with sickle cell disease.
5. Fortify food with iron and folic acid.

IODINE DEFICIENCY DISORDERS

Iodine deficiency disorder (IDD) results from inadequate intake or absorption of iodine. The
body needs only a small amount of iodine, only a teaspoon over an entire lifetime, but lack of
even trace amounts of this mineral can have a negative impact on health. People can usually get
iodine by eating a variety of foods, but the level of iodine in certain foods can vary depending on
the amount of this mineral in the soil, which edible plants absorb as they grow. The absence of

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iodine in food because of its limited availability in soil is a major cause of iodine deficiency.
Highland and mountainous regions tend to have soil with limited iodine. IDD may also result
from eating foods that decrease the rate of iodine absorption, such as cassava, turnips, and certain
cabbages and kales.

Manifestations of iodine deficiency

The severity and clinical manifestations of IDD often depend on the age when a person is
deficient in iodine. The following conditions are the most common:
Goiter: This is an enlarged thyroid gland, the most obvious sign of iodine deficiency. When a
person does not get enough iodine, the thyroid gland cannot produce certain enzymes needed for
metabolism and growth and becomes overactive, causing swelling around the neck. Goiter may
be distinguishable only on close observation or may be so large that the person cannot move the
neck. Goiter may begin to develop in adolescence as a result of iodine deficiency in childhood
and can also occur as a result of iron deficiency in adulthood.
Hypothyroidism. This condition occurs when iodine deficiency makes the thyroid less
productive, causing dry skin, weight gain, puffiness in the face, slow pulse, and lethargy.
Hypothyroidism is most common in adults.

Hyperthyroidism (Grave’s disease). This condition results from an overactive thyroid because
of iron deficiency or other causes and is characterized by a rapid pulse, considerable weight loss,
and nervousness, mainly in adults. Hyperthyroidism can be caused by both iodine deficiency and
a sudden increase in iodine by iodine-deficient populations.
Cretinism. This condition in infants and children results from inadequate iodine in the mother
during pregnancy. Children with cretinism may have severe mental retardation, physical
development problems, spastic movements, abnormal physical features, deafness, and mutism

Table 12. Recommended daily allowance (RDA) for iodine for males and females

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WATER
Water is considered an essential nutrient because it is necessary for body functions including
digestion and absorption and certain metabolic processes. Water is also a primary component of
the body, representing over 60 percent of a person’s weight. Water regularly leaves the body
through sweating, excretion, and breathing and therefore must be replaced. Adults should drink
at least 2 liters or about 8 cups of water a day. The water should be safe, clean, and boiled if
necessary. Tea, soup, milk, juice, and fruit also contain water and can help meet the body’s
needs. The caffeine in tea and coffee, however, can dehydrate the body and should be drunk in
moderation. Tea and coffee also contain substances that bind essential nutrients such as iron,
making these nutrients unavailable for the body to use.
To maintain a well-balanced diet, people should eat a variety of foods that contain all the
nutrients mentioned above in the right daily amounts and combinations to meet the body’s
functional needs.

Nutrient requirements of adults and children: Energy

Energy requirements are the “amount of food energy needed to balance energy expenditure in
order to maintain body size, body composition, and a level of necessary and desirable physical
activity consistent with long-term good health (FAO, Who, UNU 2004). Essentially, energy
requirements are the general guidelines for attaining and maintaining a health life that reflect the
body’s dietary and expenditure needs. These requirements vary according to age and gender.
Infants, children, adolescents, pregnant and lactating women, other adults, and the elderly all
have different energy requirements and should eat a well-balanced diet that takes into account
their various needs. Energy requirements are also based on the following factors:

• Basal metabolism—the minimal energy expenditure needed to maintain the basic body
functions needed for life, such as the functioning of vital organs and the nervous system. The
basal metabolic rate (BMR) is used to determine basal metabolism over a standard period of time
and can represent from 45 to 70 percent of daily energy needs.
• Metabolic response to food—the level of energy needed to digest, absorb, and utilize all
food eaten.
• Physical activity—all daily activities ranging from work to play to rest. These activities
may be occupational, associated with work, or discretionary, associated with household and
social tasks.

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• Physiological needs—Young children have added energy needs to support growth and
development. Pregnant and lactating women need additional energy to support the growth of the
fetus, the placenta, maternal tissues, and milk production (FAO, WHO, UNU 2004).

Estimating energy requirements for adults

Energy requirements and the dietary intake needed to meet these requirements may change from
day to day. These definitions are estimates of the appropriate energy for a particular group of
people. Energy requirements are measured in calories and are determined by multiplying the
BMR by an activity multiplier. The BMR is one of the most important determinants of energy
requirements. It is calculated using age, gender, height, and weight. Table 1 shows the BMR for
males and females of various ages and weight.
Equations for estimating BMR from body weight

The table above shows multiples of BMR used to determine the average daily energy
requirements of adults based on their physical activity. Activities are classified as light (e.g., the
work of an office clerk), moderate (e.g., the work of a subsistence farmer), and heavy (e.g., the
work of a laborer). The equation for determining estimated energy requirements based on
activity is kcal/day = BMR x activity factor.

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Table 2. Activity factors

As an example, to determine the estimated daily energy required by a healthy 35-yearold man
who weighs 70 kg and does heavy activity, we would multiply 2.10 x BMR, or
2.10 x (11.5 x 79 kg + 873). This would give us 3,534 kcal/day.

Determine the energy requirement of a 23-year-old woman who weighs 53 kg and does farming
and household work (moderate activity).

BMR: ______ x ______ kg + _____ = ________ kcal/day

Total kcal/day: BMR x activity factor = ________ kcal/day

Estimating energy requirements for pregnant and lactating women

The energy needs of women of reproductive age often increase because of the demands of
pregnancy, lactation, and even menstruation.
Pregnancy
During pregnancy women need extra energy and nutrients for the growth of the fetus, the
placenta, and associated maternal tissues. A pregnant woman who neglects her energy
requirements and proper diet may have a higher risk of giving birth to an unhealthy child. Energy
demands gradually increase over pregnancy, with the most energy needed during the third
trimester. However, a woman can meet her energy needs throughout the 9 months of pregnancy
if she gets the added energy in table below every day. The body can store extra energy absorbed
early in pregnancy and use it when demand increases. Energy levels differ based on activity
levels.

Table 3. Added daily energy requirements of pregnant women

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Lactation

Energy and nutrient requirements increase during lactation for milk production and secretion.
Meeting these needs is important for the health of the infant, as many nutrients provided by
breastmilk come from the mother’s diet. Table below shows the additional energy needed by
lactating women.
Table 4. Added daily energy requirements of lactating women

ESTIMATING ENERGY REQUIREMENT FOR CHILDREN AND ADOLESCENTS 1–

18 YEARS OLD

Energy requirements for adolescents, children, and infants > 1 year old are calculated taking into
account BMR, physical activity level, and energy needs for growth. Table below shows the
average daily energy requirements of this group, assuming moderate activity of the average
child.

These levels may be higher or lower depending on the physical activity of a particular child. In
general children under 10 years old have lower activity levels and energy requirements than
adolescents. During adolescence the tissues in the body change composition and grow rapidly.
Adolescents need additional energy to maintain health, promote optimal growth and nutrition,
and support physical activity.

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ENERGY REQUIREMENTS OF CHILDREN 1–18 YEARS OLD

INFANTS

The first 12 months of life are a critical time when the infant is developing and tissues are
growing. In fact, during the first 3 months of life, the body uses 35 percent of the energy it needs

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specifically for growth. Breast milk alone contains all the energy and nutrients a child needs for
the first 6 months of life. Beyond 6 months the child needs additional food supplements to
provide the appropriate level of micronutrients and macronutrients, as shown in the table below.
Infants who are undernourished or born with low birth weight may need additional energy for
catch-up growth to reach the normal height and weight of children their age.

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