Home > Encyclopedia of Food & Culture > Vitamin C

VITAMIN C. Vitamin C is also known as ascorbic acid, because it is the "anti-scorbutus" vitamin (scorbutus being the Latin name for the disease of scurvy). Unlike other vitamins, it is only required by a few species, particularly humans, but also guinea pigs and bats. Others, such as dogs and cats, make it for themselves by oxidizing glucose. Species that require the vitamin have lost the key enzyme that manufactures vitamin C because of a genetic mutation during evolution, in a period when the natural diet was vitamin C–rich, resulting in no disadvantage. The empirical formula of the vitamin is C₆H₈O₆; it is a white crystalline powder, freely soluble in water and pleasant tasting, but easily destroyed by heat and oxidation. A daily intake of as little as 7 milligrams (mg) has been found to be sufficient to prevent the development of signs of scurvy, but the usual recommendation is that adults should aim to take some 70 mg per day, partly as a safety factor. One school of thought recommends much higher intakes, of perhaps 1,000 mg, on the grounds that its antioxidant properties will increase resistance to infections, aging, and cancer. This assertion remains controversial, however. The Institute of Medicine recommends 2,000 mg/day as the tolerable upper intake level for adults. High levels may have a laxative effect, but this is welcomed by many people. The main natural sources of the vitamin are fresh fruits and vegetables. One of the first fruits valued for its antiscorbutic activity was the orange—each one containing some 50 to 75 mg of the vitamin. In contrast, an apple of similar size has only 7 mg. Potatoes have been an important source of the vitamin in some cultures, not because they are particularly rich, but because they have been consumed in large amounts.

The value of potatoes as a source of vitamin C is influenced by the way in which they are prepared. Thus, one large potato cooked in its skin in a microwave oven may supply 30 mg of the vitamin, but the same quantity may supply only a third of that or even less when boiled, mashed, and reheated on a buffet table. One problem has been to understand how Eskimos, in their traditional lifestyle, managed to obtain enough vitamin C when they had no access to fruits or vegetables. Although fully cooked meats have lost essentially all their vitamin C, the scarcity of fuel meant that the Eskimos could only bring a piece of meat just to the boil in water. They then drank the vitamin-rich broth and ate the meat, thus meeting their need for vitamin C. Liver cooked in this way is richer than muscle meats in vitamin C. Cows' milk too loses most of its vitamin C when heat-sterilized or "condensed," and infantile scurvy has been a problem where mothers have economized by using canned milk as a complete food for their infant.

See also Beriberi; Niacin Deficiency (Pellagra); Nutrient Bioavailability; Nutrients; Nutrition; Scurvy; Vitamins.

Kenneth John Carpenter