Nutritional Factors in Disease

nutritional factors in disease

THAT disease might be due to lack of some essential factor had little place in the thinking of 50 years ago. Consequently the concept of deficiency diseases, nutritional and endocrine, grew in the present century. As deficiency diseases came to be recognized and understood, the next step was the realization that lack of nutritional and endocrine factors affects primarily the chemistry of the body. Disease resulting from a ‘biochemical lesion’ and structural changes are late effects, secondary to change in function.

This revolution in medical thought had profound practical consequences. The great nutritional diseases that flourished within the lifetime of some doctors still in practice have now vanished wherever medical knowledge has been linked
with proper administration of food supplies. Florid rickets is now a clinical curiosity in Britain, yet in the streets of our big cities we still see elderly people, bandy-legged, stunted and pigeon-chested, who carry the scars of it. Pellagra, prior to 1940, affected tens of thousands of poor country people in the southern states of the USA; better knowledge of nutritional needs and, above all, improved economic circumstances have largely swept it away. The classic nutritional
diseases occur only in situations where there is a failure both of food supplies and medical care which regrettably is still the case in many parts of the world. Even in the USA, the richest country in the world, probably several million people are suffering from undernutrition or malnutrition. Those particularly liable to be affected are Negroes, Indians and ‘poor whites’ who, because of lack of education, physical or mental handicaps, alcoholism or drug addiction, are unable to obtain regular employment. It is these classes of people all over the world who tend to have large families and it is not surprising that nutritional disorders are especially liable to develop in the fourth and subsequent children.

Even in times of severe food shortage, proper application of medical knowledge can do much to overcome the worst effects of qualitative dietary deficiencies; medicine can deal with beriberi, scurvy and pellagra, but has no direct means of treating the effects of underfeeding-undernutrition. Consequently lack of sufficient food continues to be a most serious cause of ill-health in many underdeveloped regions.

The present world population is estimated to be more than 3,500 million and increasing by 70 million per year. In the absence of major catastrophes there will be more than twice as many inhabitants in the world by the year 2000 as there are today. This is not due to an increase in human fertility but is caused almost entirely by a remarkable reduction in the death rate. The greatest threat to the well-being of mankind is this explosive population growth rate. One-third of the world’s population receives less than 2,000 kcal/head/day. Agricultural production is hampered by bad climates, soil erosion, lack of fertilizers, antiquated farming methods, political upheavals and war. This situation will steadily deteriorate unless national programs of population control and family planning based on modern contraceptive techniques are evolved and effectively put into operation. In addition, food production must be greatly increased by the use of high-yielding strains of rice, wheat and maize.

 Aetiology of Nutritional Disorders

There are five essential causes of nutritional disorders:

I. Quantitative Dietary Deficiency. Not enough food results in undernutrition or when more severe, frank starvation.

2. Qualitative Dietary Deficiency. Wrong food results in malnutrition. The term ‘malnutrition’ should be restricted to those nutritional disorders, e.g. rickets and scurvy, which are due to lack of specific chemical components (nutrients) of a proper diet.

3. Quantitative Overnutrition. Too much food results in obesity.

4. Qualitative Overnutrition. This is due to too much of one food component, e.g. hypervitaminosis D.

5. Effects of Natural Toxins in Foods. Some foods contain small amounts of toxic substances which can lead to disease if a person or community has to rely too heavily on a single foodstuff, e.g. lathyrism.

Social and Economic Causes of Nutritional Disorders.

Even in countries where food, ample in quantity and quality, can be purchased, nutritional disorders arise because of poverty, prejudice, ignorance or bad housekeeping often caused by bad housing. The old, the solitary and children are most often affected.

Pathological Causes of Nutritional Disorders.

Even with an ample income, an adequate home and a knowledge of dietetics, a patient may develop a nutritional disorder through some other disease which ‘conditions’ (facilitates) it in one or more of the following ways.

DEFECTIVE INTAKE OF FOOD. (a) Loss of appetite may be an important symptom of organic disease, e.g. cancer of the stomach, and also of psychogenic disease, e.g. anorexia nervosa. (b) Persistent vomiting from any cause. (c) Food fads, e.g. in very strict vegetarians (vegans). (d) Alcohol provides calories but no essential nutrients. Chronic alcoholics suffer from malnutrition more often than undernutrition. (e) Unbalanced therapeutic diets, e.g. diets for digestive diseases may lack ascorbic acid unless care is taken to provide it. (f) Prolonged parenteral feeding with intravenous glucose after surgical operations may precipitate acute deficiencies of the vitamin B complex.

DEFECTIVE DIGESTION AND ABSORPTION. (a) Achlorhydria is a contributory factor in the causation of iron deficiency anaemia. (b) Steatorrhoea limits the absorption of fat-soluble vitamins and calcium. (c) Intestinal hurry due to surgical short circuits, etc. may impair digestion. In starving people the ingestion of unsuitable foods often causes intestinal hurry and intensifies their plight. (d) Antibiotics, if their administration is prolonged, may interfere with the production of vitamins synthesized by intestinal bacteria.

DEFECTIVE UTILISATION. (a) Cirrhosis of the liver may interfere with the proper utilization of ingested nutrients, e.g. of protein and vitamin K. (b) Malignancy, in some unknown way, may produce a state of undernutrition despite an adequate diet. The same may be true of tuberculosis and other prolonged infections. (c) In renal failure vitamin D is not converted to the active metabolite. (d) Some drugs, e.g. anticonvulsants, are antagonists of folate and of vitamin D.        ‘

LOSS OF NUTRIENTS FROM THE BODY. (a) In the nephrotic syndrome there is loss of protein in the urine. (b) In diabetes mellitus uncontrolled glycosuria causes undernutrition. (c) In excessive menstrual bleeding (menorrhagia) secondary iron deficiency anaemia is common. (d) In severe or chronic diarrhea potassium is lost.

INCREASED NUTRITIONAL NEEDS. (a) In pregnancy, lactation and adolescence (especially after an Illness in the last named), and for those engaged in hard physical work, particularly in cold climates, the usual diet may be insufficient. (b) In fevers and hyperthyroidism the increased metabolism calls for more calories. (c) After burns, fractures and major surgery, there is an increased catabolism of protein and ascorbic acid which cannot be replaced until convalescence begins.

Although nutritional disorders are often precipitated and sometimes caused by such conditioning factors, the prime cause is usually a diet deficient in one or more nutrients. It is therefore poor practice to prescribe a single nutrient (e.g. a vitamin) without first looking for evidence of other deficiencies and thereafter taking measures to improve the diet. (Nutritional Factors in Disease)