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Alternate Title

Synonyms

Antiscorbutic vitamin, ascorbate, ascorbic acid (AA), ascorbyl palmitate, calcium ascorbate, cevitamic acid, iso-ascorbic acid, l-ascorbic acid, sodium ascorbate.

Background

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. Scurvy is treated with vitamin C, and should be under medical supervision.

Many uses for vitamin C have been proposed, but few have been conclusively demonstrated as being beneficial in scientific studies. In particular, research in asthma, cancer, and diabetes remain inconclusive, while no benefits have been found in the prevention of cataracts or heart disease.

The use of vitamin C in 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 reported a significant reduction in the risk of developing a cold of 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. Overall, no significant benefits have been observed.

Evidence

Vitamin C deficiency, scurvy: Causes: 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 receiving unsupplemented milk diets. There are rare reports of scurvy due to tolerance or resistance following long-term high-dose use, including infants born to mothers taking vitamin C throughout their pregnancy. Symptoms: Initial symptoms of scurvy in adults may include loss of appetite, diarrhea, shortness of breath, weakness, and fever, followed by irritability, depression, leg pain, pseudoparalysis, swelling over long bones of the body, anemia, paleness, poor wound healing, corkscrew hair, dry eyes, skin thickening (hyperkeratosis), and bleeding (particularly gum bleeding, bleeding behind the eyes causing prominence [proptosis], bleeding at the joints of the ribs and sternum causing discoloration under the skin of the chest [costochondral beading, scorbutic rosary], skin bruising, or blood in the urine or stool). In infants, symptoms may include irritability, thigh tenderness, pseudoparalysis, bleeding around the lower ends of the leg bones (femur and tibia) causing pain, and assumption of a frog-leg posture. If left untreated, scurvy can proceed to seizures, shock or sudden death. History: Scurvy has been described since ancient Egypt, and epidemics were witnessed during the 16th-18th Centuries, in particular among sailors. In the mid-1700s, the British naval surgeon James Lind discovered that oranges and lemons, both sources of vitamin C, are effective in preventing/curing scurvy. Diagnosis: The diagnosis of scurvy is usually clinical, particularly in infants, based on symptoms, a history of vitamin C deficiency and low blood levels of ascorbic acid. Treatment: 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.
Grade: A

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 circumstances, including soldiers in sub-arctic exercises, skiers, and marathon runners, significant reductions in the risk of developing colds by approximately 50% have been reported. This area merits additional study, and may be of particular interest to elite athletes or military personnel.
Grade: B

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.
Grade: B

Alkaptonuria: Alkaptonuria is a disorder characterized by the absence of the enzyme homogentisic acid oxidase, with a resulting accumulation of homogentisic acid in the blood and urine. Limited research reports that daily high-dose vitamin C may provide symptomatic relief and slow progression of complications of this disorder. Additional evidence is merited in this area.
Grade: C

Asthma: 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 asthma has been studied since the 1980s (particularly exercise-induced asthma), although the evidence in this area remains inconclusive. Additional research is necessary before a clear conclusion can be drawn.
Grade: C

Cancer prevention: 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 it is specifically the vitamin C in these foods that is beneficial, 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 apples, asparagus, berries, broccoli, cabbage, melon (cantaloupe, honeydew, watermelon), cauliflower, citrus fruits (lemons, oranges), fortified breads/grains/cereal, kale, kiwi, potatoes, spinach, and tomatoes.
Grade: C

Cancer treatment: Vitamin C has a long history of adjunctive use in cancer therapy, and although there have not been any definitive studies using intravenous (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.
Grade: C

Plaque/ calculus on teeth: In preliminary study, a reduced amount of calculus, visible plaque and bleeding gum sites was observed after use of vitamin C chewing gum. Further research is needed to confirm these results
Grade: C

Pregnancy: The data are too few to say if vitamin C supplementation alone or combined with other supplements is beneficial during pregnancy. Preterm birth may increase with vitamin C supplementation. Although 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.
Grade: C

Stroke prevention: 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 other research reports that daily low-dose vitamin C may reduce the risk of death from stroke. Additional 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.
Grade: C

Vaginitis: 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.
Grade: C

Cataracts (prevention/progression): Although population research initially suggested a reduction in cataract formation among individuals taking vitamin C for at least 10 years, subsequent prospective research found no reduction in the seven-year risk of age-related cataract formation or progression with the use of daily vitamin C.
Grade: D

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 are infected with respiratory viruses while taking vitamin C have yielded differing results, but overall report small or no significant differences in symptom severity following infection. Notably, a subset of studies in people living in extreme circumstances, including soldiers in sub-arctic exercises, skiers, and marathon runners, have reported a significant reduction in the risk of developing a cold of approximately 50%. This area merits additional study, and may be of particular interest to elite athletes or military personnel.
Grade: D

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.
Grade: D

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.
Grade: D

Premature infants: In a randomized controlled trial, no significant benefits or harmful effects were associated with ascorbic acid supplementation throughout the first 28 days of life.
Grade: D