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 people.
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. Evidence does suggest that they do not help with cataracts or high cholesterol.
Data on vitamin C and heart disease are mixed. Some studies show that vitamin C can decrease the risk of peripheral arterial disease in women but not in men. Some research suggests that lower doses of vitamin C, in combination with vitamin E and given as slow-release formulations, might slow the progression of atherosclerosis. This combination appears to benefit both smoking and nonsmoking men but is only minimally effective in women who are postmenopausal. Studies show that patients with peripheral arterial disease seem to have lower levels of vitamin C and higher levels of C-reactive protein, which is a marker of inflammation. So it seems that taking vitamin C decreases the risk of atherosclerosis and peripheral arterial disease. It is too soon to make firm claims about preventing heart disease with vitamin C, because the data are still inconclusive. Vitamin C supplementation should not be the main focus of any patient’s treatment for 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 is associated with increased diastolic and systolic blood pressure.
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.