Vitamin C ( ascorbic acid ) helps tissue and bone grow and repair themselves. While vitamin C supplements are extremely popular, research has yet to establish solid health benefits.

Why do people take vitamin C?

Studies have shown that vitamin C may reduce the odds of getting a cold, but only in specific groups in extreme circumstances, such as soldiers in subarctic environments, skiers, and marathon runners. Studies have not found solid evidence that vitamin C helps prevent or treat colds in average situations.

Vitamin C's antioxidant benefits are also unclear. While some studies of vitamin C supplements have been promising, they have not found solid evidence that vitamin C supplements help with cancer, stroke, asthma, and many other diseases. Some evidence suggests that vitamin C may be helpful in people who have high cholesterol and in preventing cataracts, but more studies are needed to prove these effects.

Data on vitamin C and heart disease are mixed. Some studies show an association between low levels of vitamin C and heart disease risk, yet many studies have linked the use of vitamin C supplements with an increased risk of heart disease.

Data on taking vitamin C for hypertension are also mixed. Taking vitamin C with antihypertensive medications may slightly decrease systolic blood pressure, but not diastolic pressure. Supplemental vitamin C -- 500 mg per day taken without antihypertensives -- doesn't seem to reduce systolic or diastolic blood pressure. Type 2 diabetics who supplemented with vitamin C and remained on their antihypertensive medications seemed to have a reduction in blood pressure and arterial stiffness. Lower levels of vitamin C in the blood are associated with increased diastolic and systolic blood pressure.

Studies have shown that dietary rather than supplemental sources of vitamin C are more effective in keeping blood pressure in check.

A substantial number of Americans may have low intake levels of vitamin C due to the inadequate intake of fruits and vegetables. The proven and effective use of vitamin C is for treating vitamin C deficiency and conditions that result from it, like scurvy.

Vitamin C also seems to help the body absorb the mineral iron.