INDEX

Vitamin C (ascorbic acid)

Background

  • Vitamin C (ascorbic acid) is a water-soluble vitamin, which is needed by the body to form collagen in bones, cartilage, muscle, and blood vessels. 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 results in severe symptoms and can cause death. People with scurvy are treated with vitamin C and should be under medical supervision.

  • Many uses for vitamin C have been proposed, but evidence of benefit in scientific studies is lacking. In particular, research on asthma, cancer, and diabetes remains inconclusive, and a lack of benefit has been found for the prevention of cataracts or heart disease.

  • The use of vitamin C in the prevention or treatment of colds remains controversial. Extensive research has been conducted. Overall, vitamin C lacked an effect on the development of colds and on cold symptoms. However, the duration of the cold shortened slightly. Notably, people living in extreme circumstances, including soldiers in the subarctic, skiers, and marathon runners, had a 50% decrease in the risk of developing a cold. This area merits additional research and may be of particular interest to athletes or people in the military.

Scientific Evidence

Uses

Grade*

Vitamin C deficiency (scurvy)

Scurvy is caused by a lack of vitamin C in the diet. Although scurvy is uncommon, it may occur in malnourished individuals, those that need more vitamin C (such as pregnant or breastfeeding women), or infants. If vitamin C is unavailable, orange juice can be used for scurvy in infants. Symptoms should begin to improve in 1-2 days, and end completely within seven days. Treatment should be under strict medical supervision.

A

Common cold prevention (extreme environments)

Vitamin C reduced the risk of developing colds, by roughly 50% in people under physical stress or in extreme conditions, such as soldiers in the subarctic, skiers, and marathon runners. This area merits more research and may be of particular interest to elite athletes or military personnel.

B

Iron absorption enhancement

Based on scientific research, vitamin C appears to improve absorption of iron or iron supplements taken by mouth. Further research is needed to reach a firm conclusion.

B

Urinary tract infection

Vitamin C may decrease the risk of developing urinary tract infections during pregnancy and in the elderly. Further research is needed to confirm this finding.

B

Age-related macular degeneration (AMD)

There is a lack of evidence showing beneficial effects of vitamin C alone in the treatment of AMD, an eye disorder which causes loss of vision. Further research is needed in this area.

C

Alzheimer’s disease

There is limited research on the effects of vitamin C alone on the progression of Alzheimer’s disease. Further research is needed before a conclusion can be made.

C

Anemia

Research has shown that vitamin C may improve the absorption of dietary iron. Limited research has shown that vitamin C may improve outcomes of anemia, a disorder where there is a short supply red blood cells. Additional research is needed before a conclusion can be made.

C

Antioxidant

Limited research showed that vitamin C lacked a clear anti-oxidant effect. Further information is required to form conclusions.

C

Arthritis (osteoarthritis, rheumatoid arthritis)

Vitamin C may slow disease progression in individuals with osteoarthritis. However, high-quality research is needed to conclude if vitamin C is beneficial for both osteoarthritis and rheumatoid arthritis.

C

Asthma

It has been suggested that low levels of vitamin C may increase the risk of developing asthma. Research on the use of vitamin C in asthma remains inconclusive. More research is needed before a clear conclusion can be drawn.

C

Autism

Ascorbic acid may decrease the severity of symptoms in children with autism, a mental disorder. More trials are needed before a conclusion can be made.

C

Bleeding stomach ulcers caused by aspirin

Early evidence suggests that vitamin C may help with stomach damage caused by aspirin. More research is needed before a clear conclusion can be drawn.

C

Breast cancer prevention

Limited research examined the role of vitamin C in breast cancer. There was a lack of conclusive results. Additional studies are needed.

C

Burns

Early research suggested that vitamin C may have positive effects in people with severe burns. Additional studies are needed before a conclusion can be made.

C

Cancer prevention

Dietary intake of fruits and vegetables high in vitamin C has been associated with a reduced risk of cancer. The role of vitamin C is unclear. Limited research showed that vitamin C supplements lacked a protective effect on certain cancers. Further research is needed to draw conclusions.

C

Cancer treatment

Vitamin C has a long history of being used as a part of cancer therapy. Clear evidence of benefit of using vitamin C is lacking. More well-designed studies are needed before a firm conclusion can be made.

C

Chemotherapy adjunct

Early research showed that vitamin C lacked additional benefit for people with cancer when together with chemotherapy, or drug-therapy for cancer. Additional studies are needed in this area.

C

Chronic venous insufficiency

Due to limitations in research, the role of vitamin C alone is unclear in chronic venous insufficiency, a disease that occurs when insufficient blood is pumped back to the heart. Additional studies are needed.

C

Colon cancer

In limited research, vitamin C lacked an effect on colon cancer occurrence or death from cancer. Additional studies are needed before a conclusion can be made.

C

Common cold treatment

The use of vitamin C for cold symptom treatment has showed mixed results in human research. Further research is needed in this area.

C

Complex regional pain syndrome

Clinical research suggests that vitamin C may be beneficial for complex regional pain syndrome, which involves long-term pain usually in an arm or leg. Further research is needed to draw conclusions.

C

Cystic fibrosis

The role of vitamin C is unclear in people with cystic fibrosis, a disease with mucus build-up in the body. Additional research is needed in this area.

C

Dementia

The role of vitamin C alone in dementia is unclear due to the limited research that is available. Further research is needed.

C

Diabetic eye disease

In limited research, the role of vitamin C for diabetic eye disease and diabetic nerve pain was unclear. Well-designed trials are needed.

C

Endometrial cancer prevention

In human research, the effects of vitamin C supplementation are mixed regarding the prevention of endometrial cancer, a cancer of the uterus lining. Further research is needed before a conclusion can be made.

C

Erythropoietic protoporphyria (EPP)

Erythropoietic protoporphyria (EPP) is a rare inherited blood disorder characterized by extreme skin-sensitivity to sunlight. More research is needed to determine if vitamin C is beneficial for this condition.

C

Exercise recovery

Vitamin C may help prevent damage to fat and muscle caused by exercise and may improve physical ability. More research is needed before a conclusion can be made.

C

Fertility

Limited research showed that vitamin C improved pregnancy rate in women with cysts on their ovaries. Further research is needed to determine the effects of vitamin C supplementation on fertility.

C

Gallbladder disease

Vitamin C supplementation may decrease the risk of gallbladder disease in women. Well-designed trials are needed to draw conclusions.

C

Heart conditions

Early evidence suggests that vitamin C supplementation may reduce the risk of abnormal heart rhythms after surgery. Additional studies are needed.

C

H. pylori infection

Adding vitamin C to standard therapy (omeprazole, amoxicillin, and clarithromycin) for stomach ulcers due to H. pylori may allow the dose of clarithromycin to be lower. Other research showed that vitamin C lacked an effect on H. pylori infection. Further research is needed to confirm this result.

C

High blood pressure

In human research, vitamin C supplementation has been shown to decrease blood pressure. Further research is needed in this area.

C

High cholesterol

According to studies in humans, vitamin C supplementation may be beneficial in people with high cholesterol. More research is needed in this area.

C

HIV (transmission)

Supplementation of mothers with HIV disease with vitamin B, vitamin C, and vitamin E may reduce child mortality and HIV transmission through breast milk. Well-designed studies are needed.

C

Ischemic heart disease

Due to its antioxidant properties, vitamin C has been used in people with ischemic heart disease, a condition where there is insufficient blood supply to the heart. Early data suggests that vitamin C may have a benefit on blood flow in the heart. Further research is needed to confirm this finding.

C

Kidney disease

Limited research suggests that vitamin C may reduce the risk of kidney disease from the dye used in coronary angiography, a procedure to examine blood vessels. Additional trials are needed before a conclusion can be made.

C

Lead toxicity

Consuming vitamin C from dietary sources may lower blood concentrations of lead. Additional studies are needed.

C

Life extension

Research has shown that vitamin C lacked effects on extending life, or preventing mortality. Further research is needed.

C

Liver disease

Administration of vitamin C in individuals with cirrhosis may have some benefit. However, in people with chronic hepatitis C, vitamin C lacked effectiveness. Additional studies are needed before a conclusion can be made.

C

Lung disease

An oxidant-antioxidant balance may play a role in maintaining proper lung function. Limited studies have examined the role of vitamin C alone for lung diseases. Additional research is needed before a conclusion can be made.

C

Metabolic abnormalities

Limited research suggests that daily high-dose vitamin C may aid with alkaptonuria, a metabolic disorder where the urine turns black upon touching air. Also, vitamin C may improve tyrosinemia in infants, a genetic disorder of tyrosine metabolism that results in problem with the liver, kidney, and brain. Well-designed trials are needed in this area before a conclusion can be made.

C

Nitrate tolerance

Vitamin C may prevent nitrate tolerance in people using nitroglycerin under the tongue. Well-designed research is needed in this area before a conclusion can be made.

C

Nutritional support (infants)

Limited research showed a lack of benefits and harmful effects of vitamin C given for the first 28 days of life in premature infants. Additional studies are needed before a conclusion can be made.

C

Parkinson’s disease

Research showed that intake of vitamin E, vitamin C, and carotenoids may lack benefit for Parkinson’s disease. The effects of vitamin C alone are unclear. More studies are needed.

C

Physical work capacity

Limited research suggests that higher intake of vitamin C may be related to improved physical performance and muscle strength in the elderly. Well-designed trials are needed before a conclusion can be made.

C

Plaque (on teeth)

In early research, less plaque on the teeth and less bleeding of the gums were observed after the use of vitamin C chewing gum. Further research is needed to confirm these results.

C

Pneumonia (prevention)

The role of vitamin C is unclear in the prevention of pneumonia. Further research is needed to draw conclusions.

C

Pregnancy

It is unclear if vitamin C is beneficial when taken during pregnancy. It has been suggested that preterm birth may increase with vitamin C supplementation. However, early research also shows that vitamin C may lessen the chance of early water breaking. Further research is needed. A healthcare practitioner should be consulted before taking any herbs or supplements during pregnancy.

C

Pressure ulcers

Early research shows conflicting results when taking vitamin C for pressure ulcers. Further research is needed.

C

Prostate cancer

Vitamin C has been used in prostate cancer treatment. Early evidence shows that vitamin C lacks an effect on decreasing prostate cancer risk. Further research is needed for conclusions to be drawn.

C

Proteinuria (albuminuria)

Vitamin C with vitamin E may reduce albumin in the urine in people with type 2 diabetes. Further research is needed in this area.

C

Skin aging (wrinkles)

Creams with 3-10% vitamin C may improve the appearance of wrinkled skin. Further research is needed before a conclusion can be made.

C

Skin conditions

A water-based formulation of vitamin C used on the skin may decrease skin irritation after laser treatments for scar and wrinkle removal. Well-designed studies are needed for a conclusion to be drawn.

C

Skin damage caused by the sun

Limited research showed that vitamin C applied to the skin may decrease damage caused by the sun. Further research is needed to confirm this finding.

C

Skin pigmentation disorders

Limited evidence suggests that vitamin C may play a role in perifollicular pigmentation, or increased color near the hair follicle. Additional studies are needed before a conclusion can be made.

C

Stroke prevention

Evidence is mixed for the use of vitamin C for decreasing the risk of stroke. More research is needed in this area.

C

Tetanus

Tetanus is a severe infection that may be prevented by vaccination. Vitamin C may prevent death from tetanus infection. However, more high-quality studies are needed.

C

Type 2 diabetes

The effects of vitamin C in people with diabetes are mixed. Additional studies are needed.

C

Vaginitis (inflammation of the vagina)

Early research shows that vitamin C used in the vagina may help with vaginitis, or infection and inflammation of the vagina. Further research is needed to confirm this finding.

C

Cataracts (eye disease)

Research for using vitamin C for cataracts, a disease where the vision becomes cloudy, produced mixed results. Further research is needed to draw conclusions.

D

Common cold prevention (general)

Extensive research has shown that vitamin C taken by mouth lacked an effect on cold prevention.

D

Heart disease prevention

Foods containing vitamin C have been linked to a lower risk of heart disease. However, research has shown that taking vitamin C supplements lacks an effect on heart disease prevention. Further research is needed.

D

*Key to grades:

A: Strong scientific evidence for this use;

B: Good scientific evidence for this use;

C: Unclear scientific evidence for this use;

D: Fair scientific evidence against this use (it may not work);

F: Strong scientific evidence against this use (it likely does not work).

Tradition

  • ADHD, allergic rhinitis, anti-inflammatory, back pain, bedsores, bladder inflammation, blood clots, blood disorders, blood vessel disorders, bloody urine, boils, bone loss, bronchitis, bursitis (joint inflammation), cervical dysplasia (abnormal pap smear), chronic fatigue syndrome (extreme tiredness that continues), clogged arteries, connective tissue disorders, constipation, dental conditions, depression, detoxification (removing toxins), drug withdrawal, endurance, excessive menstrual bleeding, fatigue, flu, fractures, glaucoma (increased eye pressure), gout, gum disease, idiopathic thrombocytopenic purpura (blood clotting disorder), immune disorders, infectious diarrhea, inflammatory skin conditions, jellyfish stings, Lyme disease, melasma (dark skin patches), mental performance, muscle soreness, prostate inflammation, sickle cell disease (abnormal blood cells), stomach ulcer, stress, toxicity, tuberculosis, urine acidification, viral infections, wound healing.

Dosing

Adults (over 18 years old)

  • The recommended daily intake by the U.S. Food and Nutrition Board of the Institute of Medicine for men more than 18 years old is 90 milligrams of vitamin C daily; for women more than 18 years old, it is 75 milligrams daily; for pregnant women more than 18 years old, it is 85 milligrams daily; and for breastfeeding women more than 18 years old, it is 120 milligrams daily. Recently, some experts have questioned whether the recommended daily intake should be raised. Others have recommended an additional 35 milligrams daily intake in some individuals, such as smokers.

  • The upper limit of intake (UL) should avoid exceeding 2,000 milligrams daily in men or women more than 18 years old (including pregnant or breastfeeding women).

  • Vitamin C administered by mouth or injection is effective for curing scurvy. 100-250 milligrams of vitamin C was given by mouth four times daily for one week. Some experts have recommended 1-2 grams daily for two days, followed by 500 milligrams daily for one week. Symptoms should begin to improve within 24-48 hours, and be completely cured within seven days. Treatment should be under strict medical supervision. For asymptomatic vitamin C deficiency, lower daily doses may be used.

  • For antioxidant effects, 200-1,000 milligrams of vitamin C has been given daily for four weeks to a year; 300-3,000 milligrams of vitamin C has been injected into the vein, from a single dose to a duration of eight weeks.

  • For breast cancer prevention, 500 milligrams of vitamin C has been taken by mouth daily.

  • For cancer prevention, 120-2,000 milligrams of vitamin C has been taken by mouth daily for six to eight years.

  • For preventing the common cold in people in extreme environments, 200 milligrams or more of vitamin C has been taken by mouth daily for up to 14 days.

  • For preventing the common cold in general, 30-3,000 milligrams of vitamin C has been taken by mouth daily for two weeks to eight winters.

  • For treating the common cold, 200 milligrams to 3 grams have been taken by mouth daily for three to five days or longer.

  • For preventing complex regional pain syndrome in people with wrist fractures, 500 milligrams of vitamin C has been taken by mouth daily for 50 days.

  • For fertility, 750 milligrams of vitamin C has been taken by mouth daily for six months.

  • For heart conditions, 2 grams of vitamin C has been given by mouth before surgery, followed by 1 gram daily for five days.

  • For H. pylori infection, 400-1,000 milligrams of vitamin C has been given by mouth daily for up to seven weeks.

  • For high blood pressure, 60-4,000 milligrams of vitamin C has been given by mouth daily for 6-16 weeks.

  • For kidney disease, 3 grams of vitamin C was given by mouth before the kidney-toxic procedure, then 2 grams after the procedure in the evening and again the following morning; 100-200 milligrams of vitamin C has been taken by mouth daily.

  • For liver disease, 120-3,000 of milligrams vitamin C has been taken by mouth daily for one day to six months; effectiveness on liver disease was lacking.

  • For life extension, 60-2,000 milligrams of vitamin C has been taken by mouth daily for one month to 9.5 years.

  • For preventing nitrate tolerance, 3-6 grams of vitamin C has been taken by mouth daily.

  • For pregnancy, 100-1,000 milligrams of vitamin C has been taken by mouth up to four times daily during pregnancy until delivery.

  • For prostate cancer, 500 milligrams of vitamin C has been taken by mouth daily for an average of eight years.

  • For anemia, 200-300 milligrams of vitamin C has been injected into the vein three times weekly, for 3-6 months.

  • For preventing gout, 500-1,500 milligrams of vitamin C from food and/or supplements has been taken daily.

  • For skin aging, preparations containing 5-10% vitamin C were applied on the skin daily.

Children (under 18 years old)

  • The recommended daily intake by the U.S. Food and Nutrition Board of the Institute of Medicine for infants 0-12 months old is the amount of vitamin C in human milk; for children 1-3 years old, it is 15 milligrams; for children 4-8 years old, it is 25 milligrams; for children 9-13 years old, it is 45 milligrams; and for adolescents 14-18 years old, it is 75 milligrams for boys and 65 milligrams for girls. The tolerable upper intake levels (UL) for vitamin C are 400 milligrams daily for children 1-3 years old; 650 milligrams daily for children 4-8 years old; 1,200 milligrams daily for children 9-13 years old; and 1,800 milligrams daily for adolescents and pregnant and lactating females 14-18 years old.

  • For metabolic abnormalities, 100 milligrams of vitamin C has been taken by mouth.

  • For scurvy or vitamin C deficiency in children, 100-300 milligrams of vitamin C has been taken by mouth daily in divided doses for two weeks. Older or larger children may require doses closer to adult recommendations. If vitamin C is unavailable, orange juice may be used. Symptoms should begin to improve within 24-48 hours, with resolution within seven days. Treatment should be under strict medical supervision.

References

  1. Bjelakovic G, Nikolova D, Gluud LL, et al. Antioxidant supplements for prevention of mortality in healthy participants and people with various diseases. Cochrane.Database.Syst.Rev. 2012;3:CD007176. View Abstract
  2. Coombes JS and Fassett RG. Antioxidant therapy in hemodialysis people: a systematic review. Kidney Int 2012;81(3):233-246. View Abstract
  3. Cortes-Jofre M, Rueda JR, Corsini-Munoz G, et al. Drugs for preventing lung cancer in healthy people. Cochrane.Database.Syst.Rev. 2012;10:CD002141. View Abstract
  4. Dror DK and Allen LH. Interventions with vitamins B6, B12 and C in pregnancy. Paediatr.Perinat.Epidemiol. 2012;26 Suppl 1:55-74. View Abstract
  5. Evans JR and Lawrenson JG. Antioxidant vitamin and mineral supplements for slowing the progression of age-related macular degeneration. Cochrane.Database.Syst.Rev. 2012;11:CD000254. View Abstract
  6. Harrison FE. A critical review of vitamin C for the prevention of age-related cognitive decline and Alzheimer’s disease. J Alzheimers.Dis. 2012;29(4):711-726. View Abstract
  7. Hemila H and Chalker E. Vitamin C for preventing and treating the common cold. Cochrane.Database.Syst.Rev. 2013;1:CD000980. View Abstract
  8. Hovdenak N and Haram K. Influence of mineral and vitamin supplements on pregnancy outcome. Eur.J Obstet.Gynecol.Reprod.Biol. 2012;164(2):127-132. View Abstract>
  9. Juraschek SP, Guallar E, Appel LJ, et al. Effects of vitamin C supplementation on blood pressure: a meta-analysis of randomized controlled trials. Am J Clin.Nutr 2012;95(5):1079-1088. View Abstract
  10. Konrad G and Katz A. Are medication restrictions before FOBT necessary?: practical advice based on a systematic review of the literature. Can.Fam.Physician 2012;58(9):939-948. View Abstract
  11. Levis S and Theodore G. Summary of AHRQ’s comparative effectiveness review of treatment to prevent fractures in men and women with low bone density or osteoporosis: update of the 2007 report. J Manag.Care Pharm 2012;18(4 Suppl B):S1-15. View Abstract
  12. Li H, Zou Y, and Ding G. Dietary factors associated with dental erosion: a meta-analysis. PLoS.One. 2012;7(8):e42626. View Abstract
  13. Morris MC, Beckett LA, Scherr PA, et al. Vitamin E and vitamin C supplement use and risk of incident Alzheimer disease. Alzheimer Dis.Assoc.Disord. 1998;12(3):121-126. View Abstract
  14. Perez L, Heim L, Sherzai A, et al. Nutrition and vascular dementia. J Nutr Health Aging 2012;16(4):319-324. View Abstract
  15. Vodopivec-Jamsek V, de Jongh T, Gurol-Urganci I, et al. Mobile phone messaging for preventive health care. Cochrane.Database.Syst.Rev. 2012;12:CD007457. View Abstract