DAILY HUMAN REQUIREMENTS OF VITAMINS and AVITAMINOSES (Deficiencies of Vitamins)

DAILY HUMAN REQUIREMENTS OF VITAMINS

The requirement of vitamins varies considerably depending on the nature of the individual consuming them. Some general facts regarding vitamin requirement may be listed below :

1. Greater the size of the individual, higher are his vitamin needs.
2. Younger ones require higher quantities of vitamins than do the elders.
   
3. The vitamin requirements increase when a person performs exercise.
4. During ailments, the vitamin requirements are ordinarily enhanced.
5. Under certain specific conditions of metabolic disorders when the vitamins cannot be
   properly utilized, the requirement for one or more specific vitamins is at extreme.
   
6. Growing children require comparatively high quantities of vitamin D.
   
7. During pregnancy and lactation , the vitamin D requirement by the mother is greatly enhanced.
   
8. The requirements of vitamin B complex (esp., that of vitamin B1) are increased under
   conditions of greater utilization of carbohydrates.

The daily requirement of any vitamin (refer Table ) for any individual is not a fixed quantity and varies according to the rate of metabolism. In general, in all cases of high metabolic activity (such as heavy muscular work, during pregnancy and lactation and in growing children), the vitamin requirement is proportionately high. Normally, a man doing ordinary work can obtain enough vitamin from his balanced diet.
The intestinal organisms may synthesize vitamins in significant amounts and play a vital role in regulating the quantity of vitamin available to the organism. Most of the vitamins of B complex group (such as thiamine, riboflavin, nicotinic acid, pyridoxine, biotin, folic acid) and vitamain K are some of the vitamins synthesized by the intestinal organisms. These may be absorbed to varying extents and utilized. This fact renders rather ‘inaccurate’ the figures for daily requirement of the various vitamins. Certain organisms, however, destroy vitamins. Supplementing the diet with certain antibiotics and sulfa drugs enhances the growth of these organisms.
In measuring human requirements of vitamins, certain units have been used. In the beginning, these were arbitrarily fixed and were mainly based on the amount necessary to check avitaminosis in animals under standard conditions. With the passage of time, the various vitamins were synthesized and so it became possible to base the unit on the weight of purified preparations.

AVITAMINOSES
(Deficiencies of Vitamins)

A lack of one or more vitamins leads to characteristic deficiency symptoms in man. Multiple deficiencies caused by the lack of more than one vitamin are, however, more common in human beings. Vitamin deficiencies occur rather frequently in certain parts of the world for socioeconomic reasons. Avitaminosis may be of following 2 types :

• A. primary or direct— This arises due to inadequate intake of vitamins resulting from chronic alcoholism, dietary fads etc.
• B. secondary or ‘conditioned deficiency’— This arises due to other factors such as malabsorption, increased excretion, allergies, anorexia, gastrointestinal disorders etc.

Vitamin deficiency, whether primary or secondary, leads to:

1. a gradual decrease in tissue levels of the vitamin(s) deficient,
2. a biochemical lesion,
   
3. an anatomic lesion, and
4. finally cellular pathology and disease.

This sequence is schematically represented in Fig.