ECOLOGY OF MALNUTRITION
The nutritional status of individuals and population span a broad range from extremes of deficiency to excess. Malnutrition refers to cellular imbalance between the supply of nutrients and energy and the body’s demand for them to ensure growth, maintenance and specific function. It is more prevalent among developing nations, primarily those undergoing the urbanisation. Severe malnutrition is frequent during war. Protein-caloric malnutrition is most common form of undernutrition. It includes Kwashiorkor and Marasmus.
Kwashiorkor, a Ghanaian word means ‘second-child disease.” Kwashiorkor is usually associated with the period immediately following weaning, which often takes place after the birth of second child. In many parts of the world, especially in the tropics, the child is resorted from mother’s milk to a diet adequate in carbohydrates and has insufficient protein. The food usually comprises a starchy gruel made from yams, taro, corn, rice or millet. Animal protein is scarce and if available, is expensive. Thus the child may receive enough food to satisfy hunger, but does not receive the proteins vital for normal health, growth and development.
Characteristic symptoms of Kwashiorkor include edema or fluid retention in the feet, lower legs and seldom in other parts of the body. Growth and psychomotor development is retarded. Severe wasting of muscle and adipose tissue can be depicted from the thinness of upper arms. The child is unable to balance its head when pulled from a lying to sitting position. Extra vascular fluid retention distend the abdomen (potbelly).The child is apathetic, miserable, withdrawn and indifferent to its environment.
Marasmus is derived from Greek word which means withering or wasting. It results from a diet low in both protein and calories. It is more frequent among children younger than 5 years, but usually soon after weaning. Symptoms of Marasmus include extreme growth retardation, wasting of muscles and subcutaneous fat, diarrhea, and severe anemia. Since vital nutrients are absent during the period critical for brain growth, mental retardation often occurs. It results into death.
Kwashiorkor and Marasmus represent extreme examples of malnutrition and growth retardation. Lack of specific nutrients in the diet may lead to less severe form of malnutrition and other health risks.
Excessive amounts of nutrients are also hazardous to health. For example, excessive amounts of vitamin D lead to hypercalcemia, characterised by high levels of calcium in the blood. It results into sluggish nerve reflexes, weak muscles and unnatural calcification of soft tissue.
Obesity refers to excess fat accumulation which may unfavorably affect health of an individual leading to reduced life expectancy and increased health problems. An adult with BMI > 30kg/m² is said to be obese while a child is considered obese when his or her body weight is 20 per cent greater than that for his sex and age-specific weight-for-height standard. Obese children mature earlier.
DISTRIBUTION OF DEFICIENCY DISEASES
American Geographical Society has provided an eminent image of the distribution of the nutritional deficiency diseases in different parts of the world. Protein deficiency is predominantly found in the South American, African, Indian and South-East Asian populations. Mineral deficiencies predominate in Northern American continent, upper part of South-East Asian countries and some African populations. The incidence of multi-vitamin deficiencies is rampant in Africa, Middle-East and some islands of Pacific Ocean.
EFFECTS OF NUTRITIONAL STRESS
- Infant Mortality and Childhood Death
Infant mortality rate in India is very high, computed as 80/1000 live births. Prolonged nutritional stress, specifically during infancy and preschool age is a major, although indirect factor leading to infant and early childhood mortality. For instance, diarrhea usually occurs during weaning period due to combined effect of infection and low food intake.
Decreased Resistance to Infection: The resistance to infections in human is adversely affected by malnutrition.
- The skin and mucosa do not provide effective physical barriers against infection.
- Cell mediated immunity responses against bacterial infection get reduced in severely malnourished individuals. The thymus gland and thymus dependent lymphoid tissues are atrophied.
- Humoral antibodies: Circulating immunoglobulin levels are usually normal or elevated in malnourished subjects due to frequent infection. As the secretary IgA is generally reduced, recovery from infections is delayed.
Under nutrition and Learning Abilities
The period of active growth of human brain extends from 30th week of gestation to the end of the second year of life. Undernutrition during this period, appears to adversely affect the development of brain. In recent years, intensive investigations have focused on the relationship of nutritional deprivation in early life and subsequent development of brain and cognitive abilities. Evidences have been derived either from the association of malnutrition in early infancy with poor mental performance later in childhood or with the retarded brain growth or size as observed in autopsy specimens. In a study, 45 malnourished infants and age matched controls from similar sociocultural background were investigated after a period of 4-6 years. The previously malnourished group showed poor inter-sensory organisation for recognition of geometric forms. However, the differences observed by Wechsler primary and preschool Scale of Intelligence in the I.Q. were minimal.
A recent study from Brazil on nineteen marasmic children aged less than six months, successfully treated for malnutrition, did not show significant lag in their IQ compared with their siblings and peers. Thus, malnutrition does not affect intelligence or is cause of mental retardation.
NUTRITIONAL STRESS IN MODERN SOCIETY
Prior to middle age, rice was used in South East Asia and some parts of Indian subcontinent, maize in central America, potatoes in South America, wheat in South West Asia and millets in Africa and parts of China. However, during middle age, long voyages undertaken by several groups of people led to the world wide dispersion of new domestic crops and animals. Rice cultivation was brought to Africa. The potatoes were also spread to many parts of the world. Horses, donkeys, cattle, sheep etc. were introduced into America that provided essential nutrients to many native populations.
Disruption of traditional diets and introduction of new food stuffs caused nutritional stress in many societies. The estimate of such a stress in earlier times is not known completely but by the beginning of 20th century epidemics of goiter, pellagra and beriberi were evident. In urban areas, movement of people into the cash economies decreased the supply of proteins, making it costlier. Poorer sections of society in urban areas thus became victims of Kwashiorkor.
Though nutritional stresses are declining in the contemporary society, infectious diseases are being replaced by non-infectious diseases. An increased genetic heterosis is also indicated. Children in modern society are growing faster and taller. They are maturing sexually at an earlier age. However, in many third world countries the nutritional deficiency diseases are still found in a large scale.