Distribution of Ascorbic Acid
Vitamin C is distributed rather widely in nature. Important dietary sources for man include many vegetables and fruits. Canning, cooking, and other processing result in various degrees of vitamin C loss. Fresh vegetables such as broccoli, kale, parsley, and turnip greens have a high content of the vitamin, but these foods are generally not eaten in the raw state. The citrus fruits are also excellent sources and are consumed largely without processing, although for economic reasons they are not an important vitamin C source for the overall population. Certain vegetables constitute important sources by virtue of the amount eaten rather than due to a high level of the vitamin. In this class are potatoes, beans, and peas. Most animal products contain only small amounts of the vitamin. Because the vitamin of milk is largely destroyed in pasteurization or in the evaporation process, another source of vitamin C is regularly supplied to infants. By definition 1 IU or 1 USP unit is equivalent to 0.05 mg of Lascorbic acid. This makes 1 mg equal to 20 USP units.
Ascorbic Acid Requirement
The optimum human requirement for vitamin C remains a controversial matter. The recommended intakes set by the Food and Nutrition Board of the National Research Council are not necessarily based on sufficient experimental data, since such data are largely. lacking. 'l'his board [1963] recommends daily ascorbic acid intakes of 70 mg per day for adults, 100mg during pregnancy and lactation, and 30 mg for infants increasing to 80 mg in young adults. These intakes are considerably higher than many workers feel are needed. Abt and co-workers first reported the exhalation of C1402 after ingesting labeled ascorbic acid. From studies on excretion patterns of ascorbic acid these investigators set the minimum requirement for man at 1.0 to 3.0 mg daily. This is not necessarily an optimum or recommended intake and is, of course, only a fraction of that recommended by the Nutrition Board. It is certain that a large • roportion of our population has an intake considerably lower than the recommended allowances. A study of ascorbic acid intakes by' Olympic athletes in London is of interest.
The seven subjects studied in this connection ate duplicate meals, cafeteria style, for a our-day period, and these were assayed for vitamin C as well as for other nutritional constituents. The average intakes were found to be 41, 43,45, 71, 80, 81, and 98 mg of ascorbic acid per day for these subjects.
