Foods, their selection and preparation

The rarer minerals, some of which have been shown to be essential in small amounts, are normally present in all except the most highly purified foods. Because these occur generally in natural foods, their significance was not recognized until comparatively recently. So long as diets are made up largely of natural foods, any diets which provide adequate amounts of energy and protein will probably contain sufficient minerals, with the possible exception of calcium and iron. Lists of good food sources of calcium are given in Table I. Vitamins. The vitamins as a group are not closely related as to source or composi¬ tion. As each was identified as essential it was designated a "vitamin” or "required for life.” They were distinguished from each other by letter designations and later given names indicating the deficiency each pre¬ vented. As knowledge of the chemical prop¬ erties and composition of these nutrients has been developed, some have been given names descriptive of their composition. Vitamins may be placed in two subgroups on the basis of solubility, which is a clue to their food sources. Table I • Approxi¬ mate Food Calcium (milligrams1 per pound) Apples (4 ayerage-sized) . . Bananas (4 good-sized) . . Average Beef, lean . Calcium Bread, white . Bread, whole-wheat .... Content Broccoli (4 cups, cooked) of the Butter . Cabbage, headed . Edible Carrots . Cheese, Cheddar type . . . 3,960 Portion Eggs (8 or 9) . of Some Kale . Milk (scant pint) . Typical Potatoes (4 good-sized) . . Foods1 Sweet potatoes (4 good-sized) Tomatoes . Reprinted from H. C. Sherman, Principles of Nu¬ trition and Nutritive Value of Food , Miscellaneous Publication No. 546, United States Department of Agriculture, p. 17. [13] Important Vitamins FAT-SOLUBLE A including the carotins (provitamin A) D (antirachitic factor) E (antisterility factor) K (antihemorrhagic factor) WATER-SOLUBLE B a group of factors, the best known of which are Bj Thiamine (antineuritic) B2 Riboflavin Niacin (antipellagra) C Ascorbic acid (antiscorbutic) Vitamin A stimulates growth and is neces¬ sary for well-being at all ages. It is essential to the normal development and functioning of the mucous membranes of the body. An adequate amount of vitamin A is an impor¬ tant factor in keeping the linings of the re¬ spiratory, digestive, and excretory systems in a healthy condition. An early sign of vitamin A deficiency is an inflammation of the membranes of the eye, resulting in the condition known as "xerophthalmia.” If this condition is al¬ lowed to continue, it leads to blindness. This vitamin is important also in control of the adjustments made by the eyes to changes in light. Persons whose eyes adjust slowly in going from light to dark are frequently found to be on diets with inadequate amounts of vitamin A. Vitamin A is measured in terms of inter¬ national units determined by both biological and chemical methods. The fish oils are the most potent sources of this vitamin. In plant foods it occurs as one of the carotins. In the body carotins are converted to vitamin A. For this reason foods having a yellow or green color are generally rich sources of vitamin A. Green leaves, yellow corn, and sweet potatoes are better sources of vitamin A than bleached leaves, white corn, and white FOOD INTERNATIONAL UNITS