Vitamin C (ascorbic acid) is a water-soluble vitamin, which is necessary in the body to form collagen in bones, cartilage, muscle, and blood vessels and aids in the absorption of iron. Dietary sources of vitamin C include fruits and vegetables, particularly citrus fruits such as oranges.
Severe deficiency of vitamin C causes scurvy. Although rare, scurvy includes potentially severe consequences, and can cause sudden death. Patients with scurvy are treated with vitamin C and should be under medical supervision.
Many uses for vitamin C have been proposed, but few have been found to be beneficial in scientific studies. In particular, research in asthma, cancer, and diabetes remains inconclusive, and no benefits have been found in the prevention of cataracts or heart disease.
The use of vitamin C in the prevention/treatment of the common cold and respiratory infections remains controversial, with ongoing research. For cold prevention, more than 30 clinical trials including over 10,000 participants have examined the effects of taking daily vitamin C. Overall, no significant reduction in the risk of developing colds has been observed. In people who developed colds while taking vitamin C, no difference in severity of symptoms has been seen overall, although a very small significant reduction in the duration of colds has been reported (approximately 10% in adults and 15% in children). Notably, a subset of studies in people living in extreme circumstances, including soldiers in sub-arctic exercises, skiers, and marathon runners, have found a significant reduction in the risk of developing a cold by approximately 50%. This area merits additional study and may be of particular interest to elite athletes or military personnel.
For cold treatment, numerous studies have examined the effects of starting vitamin C after the onset of cold symptoms. So far, no significant benefits have been observed.
Antiscorbutic vitamin, ascorbate, ascorbic acid (AA), ascorbyl palmitate, calcium ascorbate, cevitamic acid, iso-ascorbic acid, l-ascorbic acid, sodium ascorbate.
These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.
Vitamin C deficiency (scurvy)
Scurvy is caused by a dietary deficiency of vitamin C. Although scurvy is uncommon, it may occur in malnourished individuals, those with increased vitamin C requirements (such as pregnant or breastfeeding women), or in infants whose only source of nourishment is breast milk. Vitamin C administered by mouth or injection is effective for curing scurvy. If vitamin C is not available, orange juice can be used for infantile scurvy. Symptoms should begin to improve within 24-48 hours, with resolution within seven days. Treatment should be under strict medical supervision.
Common cold prevention (extreme environments)
Scientific studies generally suggest that vitamin C does not prevent the onset of cold symptoms. However, in a subset of studies in people living in extreme climates or under extraordinary conditions, including soldiers in sub-arctic exercises, skiers, and marathon runners, vitamin C significantly reduced the risk of developing colds by approximately 50%. This area merits more study and may be of particular interest to elite athletes or military personnel.
Iron absorption enhancement
Based on scientific research, vitamin C appears to improve oral absorption of iron. Concurrent vitamin C may aid in the absorption of iron dietary supplements.
Urinary tract infection (during pregnancy)
Vitamin C may decrease the risk of developing urinary tract infections during pregnancy. Further research is needed to confirm these findings.
It has been suggested that low levels of vitamin C (or other antioxidants) may increase the risk of developing asthma. The use of vitamin C for the treatment of asthma has been studied since the 1980s (particularly exercise-induced asthma), although the evidence in this area remains inconclusive. More research is needed before a clear conclusion can be drawn.
Bleeding stomach ulcers caused by aspirin
Early evidence suggests that vitamin C may help aspirin-induced gastric damage. More research is needed before a clear conclusion can be drawn.
Dietary intake of fruits and vegetables high in vitamin C has been associated with a reduced risk of various types of cancer in population studies (particularly cancers of the mouth, esophagus, stomach, colon, or lung). However, it is not clear that a benefit comes specifically from the vitamin C in these foods, and vitamin C supplements have not been found to be associated with this protective effect. Experts have recommended increasing dietary consumption of fruits and vegetables high in vitamin C, such as asparagus, berries, broccoli, cabbage, melon (cantaloupe, honeydew, watermelon), cauliflower, citrus fruits (lemons, oranges), fortified breads/grains/cereal, kale, kiwi, potatoes, spinach, and tomatoes.
Vitamin C has a long history of adjunctive use in cancer therapy, and although there has not been any definite evidence of a benefit from injected (or oral) vitamin C, there is evidence that it has benefit in some cases. More well-designed studies are needed before a firm recommendation can be made.
Complex regional pain syndrome
Clinical study suggests that vitamin C may prevent complex regional pain syndrome among elderly female patients with wrist fracture. This area merits additional study.
Helicobacter pylori infection
Adding vitamin C to triple therapy with omeprazole, amoxicillin, and clarithromycin for
Ischemic heart disease
Due to its antioxidant properties, vitamin C has been used in patients with ischemic heart disease. Early data suggest that vitamin C may have a benefit on blood flow in the heart but more research is needed to confirm these findings.
Metabolic abnormalities (alkaptonuria)
Alkaptonuria is a disorder characterized by the absence of the enzyme homogentisic acid oxidase, which causes homogentisic acid to collect in the blood and urine. Limited research reports that daily high-dose vitamin C may provide relief of symptoms and slow progression of complications of this disorder. More study is merited in this area.
Plaque/ calculus on teeth
In early studies, reduced amounts of calculus, visible plaque, and bleeding gum sites were observed after the use of vitamin C chewing gum. Further research is needed to confirm these results
Vitamin C may play a role in the prevention of pneumonia. However, further research is needed to confirm these results.
There is not enough evidence to conclude if vitamin C supplementation alone or combined with other supplements is beneficial during pregnancy. Preterm birth may increase with vitamin C supplementation. Some study results show that daily supplementation can effectively lessen the incidence of premature rupture of chorioamniotic membranes (PROM). A gynecologist and pharmacist should be consulted before taking any herbs or supplements during pregnancy.
Vitamin C has been used in prostate cancer but there is currently a lack of evidence to determine its effect in this disease.
Skin damage caused by the sun (UVA-induced)
Vitamin C and vitamin E applied to the skin may not prevent UVA-induced skin damage (suntan). Further research is needed to confirm these findings.
Skin pigmentation disorders (perifollicular pigmentation)
Limited evidence suggests a role for vitamin C in perifollicular pigmentation, which comprises increased color pigment near the hair follicle.
There are variable results of studies that have measured the association of vitamin C intake and risk of stroke. Some studies have reported no benefits, while others report that daily low-dose vitamin C may reduce the risk of death from stroke. More research is merited in this area. Individuals at risk of having a stroke should speak with their healthcare provider about the role of vitamin C supplements in stroke prevention.
Preliminary human study shows that vitamin C vaginal tablets given once a day may help patients suffering from non-specific vaginitis. Further research is needed to confirm these findings.
Although early population research suggested a reduction in cataract formation among individuals taking vitamin C for at least 10 years, subsequent research found no reduction in the seven-year risk of age-related cataract formation or progression with the use of daily vitamin C.
Common cold prevention (general)
More than 30 clinical trials including more than 10,000 participants have examined the effects of taking daily vitamin C on cold prevention. Overall, no significant reduction in the risk of developing colds has been observed. In people who developed colds while taking vitamin C, no difference in severity of symptoms has been seen overall, although a very small significant reduction in the duration of colds has been reported (approximately 10% in adults and 15% in children). Laboratory experiments in which volunteers were infected with respiratory viruses while taking vitamin C have yielded conflicting results, but overall they reported small or no significant differences in symptom severity following infection.
Common cold treatment
Numerous studies have examined the effects of starting vitamin C after the onset of cold symptoms. Overall, no significant benefits have been observed. Initial evidence from one study reports possible benefits with high doses of vitamin C taken at the onset of symptoms, but without additional evidence this remains indeterminate. At this time, the scientific evidence does not support this use of vitamin C.
Heart disease prevention
Vitamin C does not appear to lower cholesterol levels or reduce the risk of heart attacks. Effects on cholesterol plaques in heart arteries (atherosclerosis) remain unclear, and some studies suggest possible beneficial vasodilation (artery opening) properties. Based on the current scientific evidence, vitamin C is generally not recommended for this use. People at risk of heart attacks should speak with their healthcare provider to consider preventive measures such as aspirin.
In a randomized controlled trial, no significant benefits or harmful effects were associated with ascorbic acid supplementation throughout the first 28 days of life.