MICRONUTRIENTS

There are several

nutrients

that have a role in maintaining health and preventing disease. Each nutrient has a particular function in the body and some nutrients are needed in larger quantity as compared to others. Individual requirement of each nutrient is related to age, gender, level of physical activity and state of health for e.g., in a preschooler (child between 1-3 years of age), protein requirement does not increase much but there is an increased need for all vitamins, iron, calcium, phosphorus as well as all other minerals (1) because children are active and growing rapidly. Poor nutrition in the first two years can slow a child's physical and mental development for the rest of his/her life. Apart from adequate proteins and energy, children need micronutrients to prevent illness and protect their physical and mental abilities. It has been found that children with isolated vitamin A and iron deficiency have vision difficulty and impaired physical and mental development respectively and these two are the commonest isolated nutrients deficient in both industrialized and resource poor countries.(2)

Deficiencies of vitamin D and zinc

are also common in young children. Other micronutrient deficiency is seen frequently with Protein energy malnutrition (PEM) or other systemic diseases. Iodine deficiency, selenium deficiency, vitamin C & B deficiency are seen in specific circumstances.(3)

Several trace elements and vitamins have an essential role in key metabolic pathways in the body. Common vitamins required are
- Thiamine
- Riboflavin
- Niacin
- Vitamin B6
- Vitamin B12
- Folate
- Vitamin C
- Vitamin A
- Vitamin D

Common minerals and trace elements required by the body are
- Calcium
- Phosphorus
- Magnesium
- Sodium
- Potassium
- Chloride
- Iron
- Zinc
- Copper
- Selenium
- Iodine

Preschoolers and children are highly vulnerable to micronutrient deficiencies as they have low body stores of these nutrients, they may have low intake due to improper feeding practices and increased losses due to intercurrent infections.(3)

Role of Vitamin A on growth


Vitamin A deficiency can lead to night blindness. Associations between linear growth retardation and vitamin A deficiency have been found in some, but not all studies. Age-specific paired comparisons have shown lower height-for-age, weight-for-height, mid-arm circumference and triceps skin fold in children under 3 years of age with vitamin A deficiency as compared to controls.(4) However, in infants less than 12 months of age, supplementation of vitamin A has no effect on growth and other factors may be important for growth in this age group(5) while linear growth improvement is seen in children from 12-24 months(6) Also high morbidity and mortality rates due to infectious diseases are associated with clinical and subclinical vitamin A deficiency.(7)

Role of vitamin D on growth


Vitamin D is a fat soluble vitamin that is synthesized in the skin and also absorbed from food. Factors affecting skin vitamin D production include darker skin (vitamin D production decreases with increased skin melanin), season (decreases in autumn & winter) and latitude. (Vitamin production is less in people staying above 40o N latitude or below 40o S latitude).(7) Vitamin D deficiency also occurs due to dietary deficiency. Clinically vitamin D deficiency causes rickets which leads to suboptimal linear growth and bone mineralization and bony deformities.(3)

Role of Vitamin B6 (Pyridoxine) on growth


Vitamin B6 functions as a coenzyme in the metabolism of protein, carbohydrate and fat. Vitamin B6 deficiency leads to dermatitis, microcytic anemia, seizures, depression and confusion. In infants vitamin B6 deficiency appears to adversely affect growth.(3) In a study by Heiskanen et al, it was found that infants with low pyridoxine levels experience slower length velocities.(8)

Other vitamin B deficiencies are commonly associated with PEM and include thiamine deficiency (resulting in beri beri), nicotinic acid deficiency (resulting in pellagra) and riboflavin deficiency (resulting in cheilosis and anemia). Growth affection is usually due to associated severe protein calorie malnutrition. Vitamin B12 and folic acid deficiency result in megaloblastic anemia. Vitamin C deficiency leads to scurvy and vitamin K deficiency leads to hemorrhages. Vitamin E deficiency occurs in children with fat malabsorption and leads to demyelination of spinocerebellar tracts.

Minerals & Trace Elements
Iron & growth

Iron containing compounds in the body serve metabolic or enzymatic functions or are used for storage. Hemoglobin, myoglobin, cytochromes are common iron containing compounds.

When iron reserves such as ferritin and hemosiderin are depleted, iron deficiency results in anemia. Iron deficiency in young children leads to delay in acquisition of cognitive skills and development.(3)

Zinc & growth
Zinc deficiency leads to slowly of growth (particularly affecting the lean tissue compartment), acrodermatitis enteropathica, impaired immune function and diarrhea.(7) Subclinical zinc deficiency is extremely common in resource-poor countries and is associated with stunting. Supplementation with zinc is associated with improved growth and reduced diarrheal disease morbidity.(3)

Iodine deficiency


Iodine deficiency in children can lead to impaired thyroxine synthesis leading to problems ranging from mild cognitive impairment to cretinism, delayed bone age, growth impairment and neurological deficits.(3) Treatment after clinical symptoms may not reverse these changes and thus prevention of iodine deficiency is essential. Fortification of table salt with iodine (iodized salt) is the most commonly employed means to prevent iodine deficiency.

Other trace elements such as copper deficiency can cause anemia and fractures; selenium deficiency can cause cardiomyopathy but these deficiencies are extremely rare.(3) Calcium deficiency can lead to rickets if the diet is poor in intake of dairy products or other sources of calcium which in turn causes poor mineralization of bones and suboptimal linear growth. Phosphorus deficiency is rare as phosphorus is present in all food items. Phosphorus deficiency occurs associated with diseases that lead to malabsorption and leads to rickets. Chromium deficiency leads to impaired glucose tolerance, peripheral neuropathy and encephalopathy. Fluoride deficiency can cause dental caries. Molybdenum deficiency and manganese deficiency have been reported in patients on parenteral nutrition or highly unusual diets in few case reports.

Molybdenum deficiency can cause tachycardia, tachypnea, night blindness and irritability whereas manganese deficiency can cause weight loss and hypercholesterolemia.(9)

Conclusion
Thus apart from adequate proteins and calorie intake for adequate growth, intake of micronutrients is essential to maintain optimum linear growth as well as healthy weight and to maintain proper functioning of various tissues and organs.

References
1. Nutrient Requirements and Recommendations. British Nutrition Foundation, 2004.
2. Unicef. Available on url: http://www.unicef.org. Accessed on 12th February 2009.
3. Williams AF. Pediatric Nutrition. In : Gibney MJ, Elia M, Ljungqvist O, Dowsett J (eds). Clinical Nutrition. Blackwell science. Oxford. 2006;379-427.
4. Male L et al. Nutritional and household risk factors for xerophthalmia in Aceh, Indonesia : a case-control study. American J Clin Nutrition. 1991;53:1460-1465.
5. Hadi H et al. Vitamin A supplementation selectively improves the linear growth of Indonesian preschool children : results from a randomized controlled trial. American J Clin Nutrition. 2000;71:507-513.
6. Muhilal et al. Vitamin-A fortified monosodium glutamate and health, growth and survival of children : a controlled field trial. American J Clinical Nutrition. 1988;48:1271-1276.
7. Butte NF, Lopez-Alarcon MG, Garza C. World Health Organization (WHO). Nutrient Adequacy of exclusive breast feeding for the term infant during the first six months of life. 2002, Genzeva.
8. K et al. Low vitamin B6 status associated with slow growth in healthy breast-fed infants. Pediatric Research. 1995;38:740-746.
9. Greenbaum LA. Micronutrient Mineral Deficiencies. In : Kliegman RM, Behrman RE, Jenson HB, Stanton BF (eds). Nelson Textbook of Pediatrics. Vol.1, 16th ed. Philadelphia, Saunders, 2007; 265-266.
MICRONUTRIENT STATUS OF CHILDREN IN INDIA

Multimicronutrient deficiencies

exist in children in developing countries. With decrease in severe cases of protein-energy Malnutrition, deficiencies of micronutrients in children have gained importance. According to National Nutrition Monitoring Bureau of India, over 50% of apparently healthy looking children have subclinical or biochemical deficiencies of vitamin A, vitamin B2, B6, folate and vitamin C and over 2/3rd have clinical evidence of iron deficiency(1). Jani et al found that urban slum children between 13-24 months in Mumbai were given complementary foods that were variably prepared. Most of the children were only on cereal based diets with very small amount of vegetables/fruits in the diet. Fenugreek was the only leafy vegetable included but was given to only 1-2% of children. Intake of all nutrients especially calcium and iron was low and other nutrients deficient were zinc and energy content of the feeds(2). In rural preschool children of West Bengal, 81% of children were anemic of which 91% were in 1-3 years age group(3). Although a national vitamin A prophylaxis programme has been in operation for more than 3 decades, vitamin A deficiency still continues to be a major nutritional problem. In rural preschool children of Maharashtra, prevalence of Bitot's spots (1.3%) and night blindness (1.1%) was higher than the WHO cut-off levels used to define a public health problem(4). Low vitamin B12 levels and hyper homocysteine were seen in 14% of asymptomatic Indian toddlers in a study by Hanumante et al in Pune suggestive of increased cardiovascular risk in adulthood(5). Low dietary calcium and low vitamin D intake have been found in both urban and rural children in Andhra Pradesh in a study done in 70 healthy rural children and 76 urban children(6).

This multimicronutrient deficiency in Indian children especially preschoolers is due to variety of causes. Maternal deficiency of micronutrients leads to poor fetal stores and also micronutrient deficiency in breast milk. Complementary feeds in infants are often cereal based with less fruits and vegetables, are more diluted with water especially dal and khichdi and quantity given may not be enough. Thus, intake of all nutrients becomes low. As the child grows older, it develops food preferences and becomes quite fussy to take green leafy vegetables and fruits thus compromising its intake of micronutrients from dietary sources. Staple Indian food gets replaced by Western diet such as Pizza, Burgers, Cakes and junk food which are calorie dense but micronutrient deficient especially in the higher socio-economic group. Thus, sets in an environment of multimicronutrient deficiency in children from every strata of life.

These micronutrients are required for

optimal functioning of immune system

, prevention of frequent infections, achieving optimum growth and mental development as per genetic potential of individual. Thus ensuring adequate intake of multimicronutrients in children and especially in first few years of life becomes essential to achieve these health targets.
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