Vitamin "C"

Description

What is vitamin C?

Because of its widespread use as a dietary supplement, vitamin C may be more familiar to the general public than any other nutrient. Studies indicate that more than 40% of older individuals in the U.S. take vitamin C supplements; and in some regions of the country, almost 25% of all adults, regardless of age, take vitamin C. Outside of a multivitamin, vitamin C is also the most popular supplement among some groups of registered dietitians, and 80% of the dietitians who take vitamin C take more than 250 milligrams. Why is this nutrient so popular?

Vitamin C, also called ascorbic acid, is a water-soluble nutrient that is easily excreted from the body when not needed. It's so critical to living creatures that almost all mammals can use their own cells to make it. Humans, gorillas, chimps, bats, guinea pigs and birds are some of the few animals that cannot make vitamin C inside of their own bodies.

Humans vary greatly in their vitamin C requirement. It's natural for one person to need 10 times as much vitamin C as another person; and a person's age and health status can dramatically change his or her need for vitamin C. The amount of vitamin C found in food varies as dramatically as our human requirement. In general, an unripe food is much lower in vitamin C than a ripe one, but provided that the food is ripe, the vitamin C content is higher when the food is younger at the time of harvest.

How it Functions

What is the function of vitamin C?

Vitamin C serves a predominantly protective role in the body. As early as the 1700's, vitamin C was referred to as the "antiscorbutic factor," since it helped prevent the disease called scurvy. This disease was first discovered in British sailors, whose sea voyages left them far away from natural surroundings for long periods of time. Their body stores of vitamin C fell below 300 milligrams, and their gums and skin lost the protective effects of vitamin C. Recognizing limes as a good shipboard source of vitamin C, the British sailors became known as "limeys" for carrying large stores of limes aboard ship.

The protective role of vitamin C goes far beyond our skin and gums. Cardiovascular diseases, cancers, joint diseases and cataracts are all associated with vitamin C deficiency and can be partly prevented by optimal intake of vitamin C. Vitamin C achieves much of its protective effect by functioning as an antioxidant and preventing oxygen-based damage to our cells. Structures that contain fat (like the lipoprotein molecules that carry fat around our body) are particularly dependent on vitamin C for protection.

Deficiency Symptoms

What are deficiency symptoms for vitamin C?

Full-blown symptoms of the vitamin C deficiency disease called scurvy - including bleeding gums and skin discoloration due to ruptured blood vessels - are rare in the U.S. Poor wound healing, however, is not rare, and can be a symptom of vitamin C deficiency. Weak immune function, including susceptibility to colds and other infections, can also be a telltale sign of vitamin C deficiency. Since the lining of our respiratory tract also depend heavily on vitamin C for protection, respiratory infection and other lung-related conditions can also be symptomatic of vitamin C deficiency.

Toxicity Symptoms

What are toxicity symptoms for vitamin C?

There are very few research studies that document vitamin C toxicity at any level of supplementation, and there are no documented toxicity effects whatsoever for vitamin C in relation to food and diet. At high supplemental doses involving 5 or more grams of vitamin C, diarrhea can result from the fluid in the intestine becoming too concentrated ("osmotic diarrhea").

Large supplemental doses of vitamin C can also increase levels of uric acid in the urine, because vitamin C can be broken down into uric acid. However, it is not clear that increased uric acid in the urine can increase a person's risk of forming uric acid kidney stones.

Finally, vitamin C can increase a person's absorption of iron from plant foods; and persons who have health problems related to excess free iron in their cells may want to consider avoiding high supplemental doses of vitamin C. It is important to remember that all of the above toxicity-related issues involve vitamin C in supplemental form, not as it naturally occurs in food.