NUTRITION FOR GROWTH & IMMUNITY

Why is it important to have a proper nutritious diet especially in children?
An adequate Nutrition is necessary not only for energy but also for proper growth and developing a strong immunity in the child. Children are constantly growing, developing and maturing, right from a newborn to a full grown adult. Thus a proper, balanced nutritious diet will ensure that the child grows to his maximum growth potential and also develops a strong immunity. A proper diet in childhood ensures good health as an adult. Research has shown that improper growth in infants is associated with heart and metabolic problems as an adult.

What is defined as normal growth?
A child that grows within normal range for his height and weight chart is said to be growing adequately. There are several growth charts available for reference such as NCHS growth charts (USA), WHO growth charts and Agarwal charts (India). Growth not only depends on genetic potential but also on other factors such as poverty (poverty can lead to poor food intake and improper growth), ethnic background (Asians are genetically shorter as compared to the whites) and emotional well being. Improper growth can be in form of over-nutrition (obesity) or Under-nutrition.

What is the normal growth pattern in a child?
During the 1st year of life, the child's weight increases 3 times, height by 50% and head circumference by 10 cm as compared to that at birth. The growth rate slows down in the 2nd year of life and by 24 months, children are about half of their ultimate adult height. From 2-5 years of age, weight increases only by 2 kg every year and height increases 7-8 cm every year. From 6-11 years, weight gain is about 3-3.5 kg every year and height gain is about 6-7 cm every year. During the teens, puberty occurs and with that height tends to increase. These teenagers appear lean and gawky and subsequently in later puberty weight increases to reach an adult potential by about 18 years of age.

How does development take place in various body organs?
As the child grows, maximum maturation takes place in the brain, in the gut, kidneys and various metabolic and hormonal functions of the body. Brain grows maximum in the first 2 years of life and major mental development takes place. Brain utilizes glucose as energy and thus glucose requirement is high in the 1st 2 years of life. Thus proper weaning foods after breast feeding is required to prevent any disruption in this process. At birth kidneys are immature and thus kidneys cannot tolerate a high protein load. Thus proteins are gradually increased as kidneys mature.

What are the normal energy, protein, vitamin and mineral requirements?
In an adult, of total daily energy requirements, 15% should be contributed by proteins, 50% by carbohydrates and 35% by fats of which 5% should be polyunsaturated fatty acids (PUFA). Energy requirements vary as per age and are different in boys and girls.

Infants (children less than one year of age) have a greater energy requirement as compared to adults. They require higher carbohydrates (5 gm/kg/day) and essential fatty acids along with long chain (LC-PUFA) such as arachindonic acid (ARA) and docosahexaenoic acid (DHA). Both ARA & DHA are known to be associated with better vision and cognitive development. LC-PUFA and carbohydrates should contribute about 1/3 of total energy required. They also require higher proteins per body weight as compared to an adult along with higher proportions of essential amino-acids such as leucine, isoleucine, valine, threonine, methionine, phenylalanine, tryptophan, lysine, histidine as well as cysteine, tyrosine and perhaps arginine. Since iron stores are variable in infants, routine iron supplementation of breast fed infants and use of iron fortified formulas for formula fed infants is required. Vitamin deficiencies are usually rare.

Table 1 - Energy requirement as per age (5)

Age
Energy requirement Males (Kcal)
Energy requirement Females (Kcal)
0.3 mo
545
515
4-6 mo
690
645
7-9 mo
825
765
10-12 mo
920
865
1-3 yrs
1230
1165
4-6 yrs
1715
1545
7-10 yrs
1970
1740
11-14 yrs
2220
1845
15-18 yrs
2755
2110



What is a balanced nutritious diet?
An infant should be on exclusive breast feeds till 6 months of age with appropriate weaning food being started afterwards. After 2 years of age, a diet consisting of fruits and vegetables, whole grains, low fat and non fat dairy products and beans is advocated. In children who eat non-vegetarian food, fish and lean meat is advised.

What are special nutrition requirements at different childhood ages?
Infants:
The first 4-6 months are a period of rapid growth and development. Breast milk contains all the nutrients required during this period. Exclusive breast feeding should be encouraged till 6 months of age with introduction of weaning diet after that. Weaning food should meet the requirement of iron, proteins, thiamine, niacin, vitamin B6 & B12, magnesium, zinc, sodium and chloride.

1-3 years of age: Preschools are rapidly growing and have greater energy requirement. There is increased need for all vitamins and minerals except Vitamin D & zinc. Lesser amounts of calcium, phosphorus and iron are needed as compared to earlier. Fibre (non starch polysaccharide) should also be added to meet the satiety needs. Protein requirements do not increase much.

4-6 years of age: Energy requirements continue to increase as well as proteins, vitamins except C & D) and all minerals (except iron).

7-10 years: Energy, protein, vitamin and mineral requirements increase. Requirement for thiamine, vitamin C & D remain same.

11-14 years: Protein requirement increases by 50%. Energy requirement continues to increase. Boys require increased vitamins and minerals whereas in girls iron requirement is very high and there is no change in requirement of thiamine, niacin & vitamin B6.

15-18 years: Energy, protein, vitamin and mineral requirement increases with same requirement of vitamin B12, folate, vitamin C, magnesium, sodium, potassium, chloride and copper. Calcium and iron requirement markedly increases.

What are the problems of improper nutrition on growth?
Excess nutrition can lead to obesity. Complications of obesity in children can lead to bone problems, snoring and difficulty in breathing while sleeping, high cholesterol and blood triglycerides and even high BP. The main cause of over-nutrition is eating high calorie food (junk food), sedentary life style, reduction in physical activity and increased TV, computer, video game time. Poor intake of proteins, calories and/or vitamins and minerals can lead to under-nutrition and result in poor growth, improper achievement of milestones, diarrhea and repeated infections (due to lower immunity).

Specific nutrients can affect growth.

- Protein deficiency can cause under-nutrition and growth failure.
- Vitamin A deficiency can cause eye problems and growth failure. Excess dose of vitamin A can also cause slow growth and loss of hair.
- Vitamin D deficiency can cause bone problems
- Vitamin B6 deficiency can lead to anemia and skin rash.
- Calcium deficiency can cause bone problems and growth failure
- Iron deficiency can cause anemia and growth failure
- Zinc deficiency results in poor growth, diarrhea and skin rash
- Iodine deficiency can lead to thyroid problems and impair proper mental development and can lead to growth failure
- Folic acid can lead to growth failure

What are the problems of improper nutrition on immunity?
Specific nutrient deficiency can affect the immunity for e.g. deficiency of proteins can lead to under-nutrition and affect immunity. Vitamin A deficiency can lead to breaking of skin and mucus membrane immunity. Zinc and folic acid deficiency can also affect immunity.

Improper immunity can also affect nutrition as low immunity causes infections that lead to poor intake of food, breakdown of muscle proteins and loss of energy from the body.

Thus it becomes a vicious cycle as nutrient deficiencies impair immunity and increase risk of infection which in turn leads to poor appetite.

Conclusion: Children are growing both physically and mentally and adequate nutrient supply is necessary to maintain the genetically programmed growth potential as well as immune system development. Impairment at both micronutrient as well as macronutrient level can lead to maladjustment and improper growth and development with chronic long term health consequences.
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