A Word about Caloric Requirements

The calorie requirements of individuals are influenced by many factors, and requirements may vary widely even in individuals of the same physical type living in the same environment and performing the same kind of work. Again the existence of single figures in tables of 

Committee gave consideration to the fact that calorie requirements may be influenced by health or disease, race, past and existing low levels of food intake, nutritional rehabilitation, and the character of the diet. Adjustments were suggested in relation to body size, aging, climate, activity, and growth. All of these factors may also influence vitamin requirements. 

Since much of the experimental work with vitamins has been based on their ability to increase the rate of growth, without any attention to the final state of health, it is possible that barm ultimately results from excesses of vitamins, minerals, or other nutrients. Insufficient attention has been given to this aspect of requirements. In fact there has been some tendency to provide excess vitamin intakes in foods and supplements as insurance against improper food selection, on the grounds that Excess vitamin intake over requirements with few exceptions appears to produce no toxic effects (Eddy and Dalldorf, 1944). This is a dangerous premise in the present state of knowledge and is fortunately tending to disappear. 

Vitamin A is a vitamin found in certain animal fats, such as halibut liver oil or butter, and necessary for growth and vision of animals and the health of epithelial structures. Two forms of vitamin A are known, and there are several forms of yellow plant pigments, the carotenoids, from which the human body can make vitamin A to a variable extent. 

Some confusion has occurred from the use of several standards for vitamin A and carotenes, but 1 International Unit is now referable to the activity of 0.3 ng. of pure Vitamin A alcohol (0.344 ng. vitamin A-acetate). Carotenes are transformed into vitamin A by human beings, especially in the liver and intestinal wall, but not always in the same ratio. Both carotene and vitamin A can be altered to some extent by bacteria in the intestines. 

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