Vitamin C (ascorbic acid)

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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 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 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 of people living in extreme climates or under extraordinary conditions, including soldiers in subarctic exercises, skiers, and marathon runners, vitamin C significantly reduced the risk of developing colds, by approximately 50%. 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 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 this finding. 		B
Age-related macular degeneration (AMD)
There is a lack of evidence showing the beneficial effects of vitamin C alone in the treatment of AMD. 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
Vitamin C may enhance the absorption of dietary iron, but additional research is needed before a conclusion can be made. 		C
Arthritis (osteoarthritis and rheumatoid arthritis)
Consumption of vitamin C may reduce the risk of cartilage loss and disease progression in individuals with osteoarthritis. However, more well-designed clinical trials are needed to determine if vitamin C is beneficial for osteoarthritis or rheumatoid arthritis. 		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 the treatment of asthma (particularly exercise-induced asthma) has been studied since the 1980s, although the evidence in this area 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. 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 aspirin-induced gastric damage. More research is needed before a clear conclusion can be drawn. 		C
Breast cancer (prevention)
Some studies have examined a link between the consumption of fruits and vegetables and the prevention of breast cancer. However, the exact role of vitamin C is unclear. Additional studies are needed. 		C
Burns
Ascorbic acid administration to patients with severe burns significantly reduced resuscitation fluid volume requirements, body weight gain, and wound edema. 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 various types of cancer in population studies (particularly cancers of the mouth, esophagus, stomach, colon, or lung). However, it is not clear that the benefit came 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, and cereal; kale; kiwi; potatoes; spinach; and tomatoes. 		C
Cancer treatment
Vitamin C has a long history of use as an adjunct 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 there is benefit in some cases. More well-designed studies are needed before a firm recommendation can be made. 		C
Chemotherapy (adjunct)
Vitamin C did not demonstrate a significant advantage over placebo as an adjunct to chemotherapy, as measured by an increase in survival or by tumor response. Additional studies are needed in this area. 		C
Chronic diseases (mortality prevention)
Vitamin C in high doses may have beneficial effects on acute inflammation and blood vessel functioning. However, the exact role of vitamin C in chronic diseases is unclear, and more high-quality human studies are needed. 		C
Chronic venous insufficiency
The role of vitamin C alone in chronic venous insufficiency cannot be determined with the available evidence. Additional studies are needed. 		C
Colorectal cancer
Vitamin C has not been shown to decrease total cancer incidence or cancer mortality. Additional studies are needed before a conclusion can be made. 		C
Complex regional pain syndrome
Clinical research suggests that vitamin C may prevent complex regional pain syndrome among elderly female patients with wrist fracture. Additional studies suggest that vitamin C may help to reduce pain associated with this syndrome. 		C
Cystic fibrosis
The role of vitamin C in patients with cystic fibrosis is currently unclear. Additional research is needed in this area. 		C
Diabetic retinopathy
A review included four studies of the relationship between vitamin C alone and diabetic neuropathy. However, there was a lack of studies that administered vitamin C to determine if it had any effects on symptoms associated with this condition. Well-designed trials are needed. 		C
Endometrial cancer (prevention)
Based on studies included in a review, the effects of vitamin C supplementation on the prevention of endometrial cancer are mixed. Further research is needed before a conclusion can be made. 		C
Erythropoietic protoporphyria (EPP)
Erythropoietic protoporphyria (EPP) is a rare inherited disease characterized by dermal photosensitivity due to the accumulation of photosensitizer protoporphyrin IX. More research is needed to determine if vitamin C is beneficial for this condition. 		C
Exercise recovery
Vitamin C may prevent endurance exercise-induced oxidative damage to fat and muscle tissue in healthy people. More research is needed before a conclusion can be made. 		C
Gallbladder disease
Vitamin C supplementation and increased vitamin C serum levels may decrease the risk of developing gallbladder disease in women. Well-designed trials are needed. 		C
Heart conditions (heart protection during chemotherapy)
There is currently a lack of studies that have examined the effects of vitamin C alone for heart-protective effects in patients receiving chemotherapy. Additional studies are needed. 		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 this result. 		C
High blood pressure
Dietary restriction of vitamin C may be associated with increases in both diastolic and systolic blood pressure. Vitamin C supplementation has been shown to decrease systolic and diastolic blood pressure. Further research is needed in this area. 		C
High cholesterol
According to studies in humans, vitamin C supplementation may have beneficial effects in patients with high cholesterol. More research is needed in this area. 		C
HIV (transmission)
According to secondary sources, 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 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 this finding. 		C
Kidney disease (contrast-induced nephropathy prevention)
Vitamin C before and after coronary angiography may reduce the risk of developing contrast-mediated kidney disease. According to a trial included in a systematic review, a significant reduction in contrast-mediated kidney disease was observed. 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
Liver disease
Administration of vitamin C in individuals with cirrhosis may have some benefit. However, in patients with chronic hepatitis C, vitamin C was not effective. 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 well-designed trials are needed before a conclusion can be made. 		C
Metabolic abnormalities
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 research is merited in this area. Oral or intramuscular vitamin C may improve tyrosinemia (genetic tyrosine metabolism disorder resulting in liver, kidney, and brain disorders) in premature infants on high-protein diets. Well-designed trials are needed in this area before a conclusion can be made. 		C
Nitrate tolerance
Oral vitamin C may prevent the development of nitrate tolerance in patients taking sublingual (under the tongue) nitroglycerin. Furthermore, short-term vitamin C may prevent attenuation of tolerance to the blood vessel widening effects of nitrate. Well-designed trials are needed in this area before a conclusion can be made. 		C
Nutritional support (premature infants)
Benefits or harmful effects of ascorbic acid supplementation throughout the first 28 days of life were not found in one study. Additional studies are needed before a conclusion can be made. 		C
Parkinson's disease
Intake of vitamin E, vitamin C, and carotenoids may not be beneficial for symptoms associated with Parkinson's disease. The effects of vitamin C alone cannot be determined from these studies. More studies are needed. 		C
Physical work capacity
Population-based research suggests that higher dietary intake of vitamin C may be associated with improved physical performance and muscle strength in the elderly. Well-designed trials are needed before a conclusion can be made. 		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 available study 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
Pressure ulcers
Vitamin C supplementation may be effective for reducing pressure sore areas. However, the results of the available studies in humans are conflicting. 		C
Prostate cancer
Vitamin C has been used in prostate cancer treatment. The current evidence is mixed, and it is unclear whether vitamin C is beneficial for individuals with prostate cancer. 		C
Proteinuria (albuminuria)
Vitamin C plus vitamin E may reduce the excretion of albumin in patients with type 2 diabetes. Further research is needed in this area. 		C
Skin aging (wrinkles)
Topical preparations containing 3-10% vitamin C may improve the appearance of wrinkled skin, as evidenced by improved fine and coarse wrinkling, yellowing and sallowness, roughness, and skin tone. Well-designed trials are needed in this area before a conclusion can be made. 		C
Skin conditions (erythema)
A water-based formulation of vitamin C used on the skin may decrease skin irritation following laser treatments for scar and wrinkle removal. Well-designed studies are needed. 		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 this finding. 		C
Skin pigmentation disorders (perifollicular pigmentation)
Limited evidence suggests a role for vitamin C in perifollicular pigmentation, which is increased color pigment near the hair follicle. Additional studies are needed before a conclusion can be made. 		C
Stroke prevention
There are variable results of studies that have measured the association of vitamin C intake and the 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 providers about the role of vitamin C supplements in stroke prevention. 		C
Tetanus
Tetanus is a severe infection that may be prevented by vaccination. In developing countries, vaccination coverage is not always high, and in developed countries, cases may still occur, particularly in elderly people, owing to their reduced immune system functioning. It has been estimated that there are about one million cases of tetanus per year globally. Vitamin C may prevent mortality from tetanus infection. However more high-quality human studies are needed. 		C
Type 2 diabetes
The effects of vitamin C in patients with diabetes are mixed. Additional studies are needed. 		C
Vaginitis
Preliminary human research shows that vitamin C vaginal tablets given once daily may help patients suffering from nonspecific vaginitis. Further research is needed to confirm this finding. 		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, a significant reduction in the risk of developing colds has not been observed. In people who developed colds while taking vitamin C, no difference in the severity of symptoms has been seen overall, although a 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, some studies in people living in extreme circumstances, including soldiers in subarctic exercises, skiers, and marathon runners, have reported a significant reduction in the risk of developing a cold, by approximately 50%. This area merits additional research 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 reported 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. Its effects on cholesterol plaques in heart arteries (atherosclerosis) remain unclear, and some studies have suggested 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 providers to consider preventive measures such as aspirin. 		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)

Grading rationale

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 healthcare provider.

Acne, aging, anti-inflammatory, atherosclerosis (hardening of the arteries), attention-deficit hyperactivity disorder, bedsores, blood disorders (idiopathic methemoglobinemia, hematuria), blood vessel disorders (capillary fragility), bronchitis, bursitis, cervical dysplasia, chronic fatigue syndrome (CFS), cognitive function, connective tissue disorders (collagen disorders), constipation, cystitis, dementia, dental conditions (discoloration of tooth enamel, dental cavities, pyorrhea), depression, dermatitis, detoxification (histamine), drug withdrawal, dysentery, endurance, eye disorders (glaucoma), fatigue, fractures, furunculosis (recurrent boils), gastric ulcer, gout, gum disease, hay fever, hemorrhage (retinal), idiopathic thrombocytopenic purpura, immune disorders (Chediak-Higashi syndrome, immune stimulation), infertility, influenza (swine), jellyfish stings, Lyme disease, melasma, menorrhagia (heavy menstrual bleeding), muscle soreness, pain (back pain, fractures), prostatitis, sickle cell disease, stomach ulcers, stress, thrombosis (vascular), toxicity (levodopa, interferon, aspirin, arsenic, mercury elimination), tuberculosis, urine acidification, viral infections, wound healing.

Dosing Related terms
NS_patient-vitaminc Portions of this document last updated: Sept. 1, 2012

THIS EVIDENCE-BASED MONOGRAPH WAS PREPARED BY
THE NATURAL STANDARD RESEARCH COLLABORATION
(www.naturalstandard.com)

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