Ecology of Nutritional Deficiency Diseases
Attention to communicable diseases may tend to mask the prevalence of a great variety of diseases that are the result of undernutrition as well as malnutrition. With a very large number of people living in extreme poverty in South Asia, dietary deficiencies are to be expected.
Although “diseases of poverty” do not constitute a special category in the official International List of Disease Classification, the international medical community is increasingly cognizant of such a class (Prost 1988). M. S. R. Hutt and D. P. Burkitt (1986) go so far as to say that “most so-called tropical diseases are, in fact, diseases of poverty, rather than of geography.” On the basis of his field studies on the nutrition of children in Haryana, S. K. Aggarwal (1986) found that “no other factor seems to affect the nutritional status of the children as much as family income.” The scientific concept of balanced diet in South Asia is only of academic importance; the real concern is dietary sufficiency.The Indian Council of Medical Research found in its surveys that about 35 percent of children have protein-calorie malnutrition (Mitra 1985). Earlier emphasis on protein deficiency has given way to the more widely acceptable concept of protein-calorie malnutrition (PCM) or protein-energy malnutrition (PEM) (Learmonth 1988). India, Bangladesh, and Nepal together have a serious problem of malnutrition and hunger, even though in recent years agricultural production has been rising, especially in India. The situation in Pakistan and Sri Lanka is, on the average, “adequate,” but in India, Bangladesh, and Nepal, less than 90 percent of the average daily energy requirements are met.
The relationship between food in the market and its availability to an individual for actual consumption depends on a host of intervening factors (Aggar- wal 1986). Among these factors are family income, gender, age, season of the year, government regulations, and cultural factors such as dietary restrictions, taboos, and preferences.
Addressing the role of cultural dietary preferences in disease ecology, A. K. Chakravarti (1982) provides evidence to show that existing regional differences do translate into a significantly higher incidence of diet-related diseases. These facts were earlier noted by J. M. May (1961). In predominantly rice-eating areas, where highly polished rice is preferred, beriberi is preeminent, because of thiamine deficiency, which results from the polishing process. Where parboiled rice is widely employed, however, the incidence of beriberi is claimed to be significantly lower. Consumption of khesari as the basic pulse in eastern Madhya Pradesh has been associated (Chakravarti 1982) with the incidence of lathyrism, which is characterized by muscular atrophy, causing the typical “scissors gait,” incontinence of urine, and sexual impotence (Manson-Bahr 1966).The impact of malnutrition is not easily measured, but some of the effects are well known and include anemia, goiter, night blindness, rickets, beriberi, and probably permanent damage to the nervous system, resulting in mental disorders. The long-term economic, social, and personal impact of these dietary deficiencies can only be imagined. In addition, Undemutrition of pregnant mothers has adverse consequences both for them and for their babies, who are often of low-birthweight. It is a well- established fact that low-birthweight is a major correlate of infant mortality. Thus low-income, undernourished mothers are likely to have a higher frequency of low-birthweight babies, and thus contribute disproportionately to higher infant mortality. Even in the same village infant mortality among the poor is twice that of the privileged people (Mitra 1985).
Some of the nutritional deficiency diseases have a clear regional prevalence. Goiter, for example, has a high rate of endemicity in a Sub-Himalayan belt extending from Arunachal Pradesh and other states in northeast India through Bhutan, West Bengal, Sikkim, Bihar, Nepal, Uttar Pradesh, Himachal Pradesh, Jammu, and Kashmir.
Goiter is also found in parts of Gujarat, Madhya Pradesh, and Maharashtra (India 1987). Endemic goiter is primarily due to a dietary iodine deficiency, resulting in enlargement of the thyroid gland. At one time considered only an unsightly inconvenience, goiter is now known to be a possible precursor of cancer of the thyroid, and is associated with below normal mental and physical development. It is also possible that very high infant mortality in these regions is related to regional iodine deficiency (Hutt and Burkitt 1986). The government of India in 1983 launched a major program, through both private and public channels, of iodizing salt, in an effort to combat iodine deficiency and decrease goiter incidence.Every culture has some distinctive practices that may be associated with culture-specific diseases. For example, only in Kashmir do people use an earthen pot (Jiangri) containing live coal, nestled in a wicker basket, that hangs by a thread around their neck during the winter season, as a portable personal body warmer. Heat and irritation from this kangri practice is significantly associated with the kangriburn cancer, especially among the elderly (Manson- Bahr 1966). Similarly, cancer of the buccal cavity is found to be associated with the long-term habit of chewing betel. This habit is common in eastern Ganga Plain and southwestern India.