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Vitamin C

Natural Standard Monograph, Copyright © 2009 (www.naturalstandard.com). Commercial distribution prohibited. This monograph is intended for informational purposes only, and should not be interpreted as specific medical advice. You should consult with a qualified health care professional before making decisions about therapies and/or health conditions.

Related Terms

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. 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.

Evidence

Uses based on scientific evidence 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 professional.	Grade*
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.	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 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.	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.	B
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.	B
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 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.	C
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.	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 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.	C
Cancer treatment 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.	C
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.	C
Helicobacter pylori infection Adding vitamin C to triple therapy with omeprazole, amoxicillin, and clarithromycin for Helicobacter pylori gastric ulcer treatment may allow the dose of clarithromycin to be lower. Further research is needed to confirm these results.	C
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.	C
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.	C
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	C
Pneumonia (prevention) Vitamin C may play a role in the prevention of pneumonia. However, further research is needed to confirm these results.	C
Pregnancy 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.	C
Prostate cancer Vitamin C has been used in prostate cancer but there is currently a lack of evidence to determine its effect in this disease.	C
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.	C
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.	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 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.	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.	C
Cataracts (prevention/progression) 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.	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 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.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.	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.	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.	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.	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).

For full grading rationale, click here.

Uses based on tradition or theory

The below uses are based on tradition or scientific theories. They often have not been thoroughly tested in humans, and safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified health care professional

Acne, Alzheimer's disease, anemia, anemia in hemodialysis patients, antiviral, antioxidant, atherosclerosis (hardening of the arteries), attention deficit hyperactivity disorder, autism, bronchitis, capillary fragility, cervical dysplasia, Chediak-Higaski syndrome, constipation, cystic fibrosis, delayed onset muscle soreness, dental cavities, dermatitis, diabetes, eye disorders, fluorosis (discoloration of tooth enamel), furunculosis (recurrent boils), gallbladder disease, gastric ulcer, hay fever, high blood pressure, high cholesterol, histamine detoxification, idiopathic thrombocytopenic purpura, immune stimulation, infertility, jellyfish stings, lead toxicity, male infertility, macular degeneration, melasma, menorrhagia, heavy metal/lead toxicity (mercury elimination), nitroglycerin activity prolongation (nitrate tolerance prevention), osteoporosis, pressure sores, reduction of levodopa side effects, reflex sympathetic dystrophy, skin conditions (wrinkles), stomach ulcers, tuberculosis, urinary acidification, wound healing.

Safety

The U.S. Food and Drug Administration does not strictly regulate herbs and supplements. There is no guarantee of strength, purity or safety of products, and effects may vary. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare professional before starting a new therapy. Consult a healthcare professional immediately if you experience side effects.

Allergies

Patients should avoid vitamin C products if they are sensitive or allergic to any of their ingredients.

Side Effects and Warnings

Vitamin C is generally regarded as safe in amounts obtained from foods. Vitamin C supplements are also generally regarded as safe in most individuals in recommended amounts, although there are rarely reported side effects including nausea, vomiting, heartburn, abdominal cramps, and headache. Dental erosion may occur from chronically chewing vitamin C tablets.
High doses of vitamin C have been associated with multiple adverse effects. These include kidney stones, severe diarrhea, nausea, and gastritis. Rarely, flushing, faintness, dizziness, and fatigue have been noted. Large doses may precipitate hemolysis (red blood cell destruction) in patients with glucose 6-phosphate dehydrogenase deficiency. High doses of vitamin C should be avoided in people with conditions aggravated by acid loading, such as cirrhosis, gout, renal tubular acidosis, or paroxysmal nocturnal hemoglobinuria. Parenteral (injected) vitamin C may cause dizziness, faintness, injection site discomfort, and in high doses may lead to renal insufficiency (kidney function problems). In cases of toxicity due to massive ingestions of vitamin C, forced fluids and diuresis may be beneficial.
Healthy adults who take chronic large doses of vitamin C may experience low blood levels of vitamin C when they stop taking the high doses and resume normal intake. To avoid this potential complication, people who are taking high doses who wish to reduce their intake should do so gradually rather than acutely. There are rare reports of scurvy due to tolerance or resistance following cessation after long-term high-dose use, such as in infants born to mothers taking extra vitamin C throughout their pregnancy.

Pregnancy and Breastfeeding

Vitamin C intake from food is generally considered safe during pregnancy. However, it is not clear if vitamin C supplementation in amounts exceeding Dietary Reference Intake recommendations is safe or beneficial. There are rare reports of scurvy due to tolerance/resistance in infants born to mothers taking extra vitamin C throughout their 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.
Vitamin C is present in breast milk. Vitamin C intake from food is generally considered safe in breastfeeding mothers. Limited research suggests that vitamin C in breast milk may reduce the risk of the development of childhood allergies. It is not clear if vitamin C supplementation in amounts exceeding Dietary Reference Intake recommendations is safe or beneficial.

Interactions

Most herbs and supplements have not been thoroughly tested for interactions with other herbs, supplements, drugs, or foods. The interactions listed below are based on reports in scientific publications, laboratory experiments, or traditional use. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare professional before starting a new therapy.

Interactions with Drugs

Vitamin C may increase adverse effects associated with acetaminophen or aluminum-containing antacids such as aluminum hydroxide (Maalox®, Gaviscon®).
Vitamin C may increase blood levels and adverse effects of aspirin, whereas aspirin may decrease blood levels of vitamin C.
The effects of vitamin C may be decreased by barbiturates including phenobarbital (Luminal®, Donnatal®), pentobarbital (Nembutal®), or secobarbital (Seconal®).
Vitamin C supplementation may decrease levels of the drug fluphenazine in the body.
Concomitant administration of high doses of vitamin C can reduce steady-state indinavir plasma concentrations.
There is limited case report evidence that high dose vitamin C may reduce side effects of levodopa therapy such as nausea or malcoordination.
Nicotine products such as cigarettes, cigars, chewing tobacco, or nicotine patches may decrease the effects of vitamin C.
Oral estrogens may decrease the effects of vitamin C in the body. When taken together, vitamin C may increase blood levels of ethinyl estradiol.
The effects of vitamin C may be decreased by tetracycline antibiotics such as doxycycline (Vibramycin®), minocycline (Minocin®), or tetracycline (Sumycin®).
Vitamin C in high doses appears to interfere with the blood thinning effects of warfarin by lowering prothrombin time (PT), as noted in case reports in the 1970s. Complications have not been reported (such as increased blood clots).
High doses of vitamin C are not recommended in patients with kidney failure. Caution is advised when taking vitamin C and drugs that may damage the kidneys due to an increased risk of kidney failure.

Interactions with Herbs and Dietary Supplements

When taken together, vitamin C may increase the absorption of iron in the gastrointestinal tract, although this effect appears to be variable and may not be clinically significant.
Vitamin C may increase absorption of lutein vitamin supplements.
Large doses of vitamin C may interfere with the absorption and metabolism of vitamin B12.
In theory, large doses of vitamin C may also interact with herbs and supplements with hormonal, antibacterial and blood thinning (anticoagulant) activity.
Caution is advised when taking vitamin C and agents that may damage the kidneys due to an increased risk of kidney failure.

Authors

This information is based on a professional level monograph edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (www.naturalstandard.com).

Selected References

Natural Standard developed the above evidence-based information based on a systematic review of the available scientific articles. For comprehensive information about alternative and complementary therapies on the professional level, go to www.naturalstandard.com. Selected references are listed below.

Casanueva E, Ripoll C, Tolentino M, et al. Vitamin C supplementation to prevent premature rupture of the chorioamniotic membranes: a randomized trial. Am J Clin Nutr 2005;81(4):859-863.
Chuang CH, Sheu BS, Kao AW, et al. Adjuvant effect of vitamin C on omeprazole-amoxicillin-clarithromycin triple therapy for Helicobacter pylori eradication. Hepatogastroenterology 2007 Jan-Feb;54(73):320-4.
Douglas RM, Hemilä H, Chalker E, et al. Vitamin C for preventing and treating the common cold. Cochrane Database Syst Rev 2007 Jul 18;(3):CD000980.
Duconge J, Miranda-Massari JR, et al. Vitamin C pharmacokinetics after continuous infusion in a patient with prostate cancer. Ann Pharmacother 2007 Jun;41(6):1082-3.
Ehrlich M, Rao J, Pabby A, et al. Improvement in the appearance of wrinkles with topical transforming growth factor beta(1) and l-ascorbic acid. Dermatol Surg 2006 May;32(5):618-25.
Hemilä H, Louhiala P. Vitamin C for preventing and treating pneumonia. Cochrane Database Syst Rev 2007 Jan 24;(1):CD005532.
Inui S, Itami S. Perifollicular pigmentation is the first target for topical vitamin C derivative ascorbyl 2-phosphate 6-palmitate (APPS): randomized, single-blinded,placebo-controlled study. J Dermatol 2007 Mar;34(3):221-3.
Konturek PC, Kania J, Hahn EG, et al. Ascorbic acid attenuates aspirin-induced gastric damage: role of inducible nitric oxide synthase. J Physiol Pharmacol 2006 Nov;57 Suppl 5:125-36.
McNulty PH, Robertson BJ, Tulli MA, et al. Effect of hyperoxia and vitamin C on coronary blood flow in patients with ischemic heart disease. J Appl Physiol 2007 May;102(5):2040-5.
Muran PJ. Mercury elimination with oral DMPS, DMSA, vitamin C, and glutathione: an observational clinical review. Altern Ther Health Med 2006 May-Jun;12(3):70-5.
Nankivell BJ, Murali KM. Images in clinical medicine. Renal failure from vitamin C after transplantation.N Engl J Med 2008 Jan 24;358(4):e4.
Ochoa-Brust GJ, Fernández AR, Villanueva-Ruiz GJ, et al. Daily intake of 100 mg ascorbic acid as urinary tract infection prophylactic agent during pregnancy. Acta Obstet Gynecol Scand 2007;86(7):783-7.
Petersen EE, Magnani P. Efficacy and safety of vitamin C vaginal tablets in the treatment of non-specific vaginitis. A randomised, double blind, placebo-controlled study. Eur J Obstet Gynecol Reprod Biol 2004;117(1):70-75.
Puvabanditsin P, Vongtongsri R. Efficacy of topical vitamin C derivative (VC-PMG) and topical vitamin E in prevention and treatment of UVA suntan skin. J Med Assoc Thai 2006 Sep;89 Suppl 3:S65-8.
Zollinger PE, Tuinebreijer WE, Breederveld RS, et al. Can vitamin C prevent complex regional pain syndrome in patients with wrist fractures? A randomized, controlled, multicenter dose-response study. J Bone Joint Surg Am 2007 Jul;89(7):1424-31.

Vitamin B12

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