Chapter 19 - Sources of the Vitamins

Abstract

The total vitamin intake of a human or animal is the sum of the amount of bioavailable vitamins consumed in foods/feedstuffs and any supplements. Estimates of the vitamin contents of most foods and feedstuffs are available from different sources, including the USDA's National Nutrient Database, which has compiled the nutrient content of foods common to the American diet. Most humans consume the vast majority of their vitamins from 50 to 200 core food items. In less developed nations, people rely on staple foods, such as wheat, rice, and corn (maize), for most of their vitamins. Bioavailability and vitamin losses are important considerations in meeting requirements for humans and animals. A number of extrinsic factors, such as chemical and physical form, and intrinsic factors, such as age and health status affect the bioavailability of vitamins. Vitamin losses occur due to storage, milling, processing, and cooking. National programs mandate the fortification of particular foods with vitamins in a number of nations to include the fortification of folate to wheat products in the United States. Dietary supplements are also meaningful contributors of vitamins to the diet, particularly in developed nations.