Section 12. Disorders of Nutrition and Metabolism

Chapter 154. Vitamins

Topics: Introduction | Vitamin A | Vitamin D | Vitamin E | Vitamin K | Vitamin B1 | Vitamin B2 | Niacin | Vitamin B6 | Vitamin B12 | Folic Acid | Vitamin C

Vitamin C

Vitamin C (ascorbic acid) is essential for the formation of bone and connective tissue (which binds other tissues and organs together). Vitamin C helps the body absorb iron, and it helps burns and wounds heal. Like vitamin E, vitamin C is an antioxidant: It protects cells against damage by free radicals, which are reactive by-products of normal cell activity.

Vitamin C Deficiency

Vitamin C deficiency causes scurvy. In adults, the deficiency usually results from a diet low in vitamin C. For example, vitamin C deficiency may develop in people who eat only such foods as dried meat, tea, toast, and canned vegetables. Pregnancy, breastfeeding, surgery, and burns can significantly increase the body's requirements for vitamin C and the risk of vitamin C deficiency. Smoking increases the vitamin C requirement by 30 to 50%.

Scurvy in infants is rare because breast milk usually supplies enough vitamin C and infant formulas are fortified with the vitamin.

In adults, a few months of a diet low in vitamin C can cause bleeding under the skin (particularly around hair follicles or as bruises), around the gums, and into the joints. Symptoms may include irritability, depression, weight loss, fatigue, and general weakness. The gums become swollen, purple, and spongy. The teeth eventually loosen. Infections may develop, and wounds do not heal.

In infants, symptoms include irritability, pain during movement, and loss of appetite. Infants do not gain weight as they normally do. Bone growth is impaired, and bleeding and anemia may occur.

The diagnosis of scurvy is based on symptoms. Blood tests detect a very low level of vitamin C. Scurvy is treated with daily vitamin C supplements. Such treatment plus iron supplements can cure the anemia.

Vitamin C Excess

Some people take high doses of vitamin C because it is an antioxidant, which protects cells against damage by free radicals. Free radicals, which are reactive by-products of normal cell activity, are thought to contribute to many disorders, such as atherosclerosis, cancer, lung disorders, the common cold, eye cataracts, and memory loss. Whether taking high doses of vitamin C protects against these disorders is unclear. Evidence of a protective effect against cataracts is strongest. In any case, high doses (up to the safe upper limit) of vitamin C are usually not toxic, although they occasionally cause nausea or diarrhea and interfere with the interpretation of some blood test results.