Vitamin C is a vital nutrient for health. It helps form and maintain bones, skin, and blood vessels. It occurs naturally in some foods, especially, fruit and vegetables. Supplements are also available.
It is also known as L-ascorbic acid, ascorbic acid, or L-ascorbate.
Vitamins, including vitamin C, are organic compounds. An organic compound is one that exists in living things and contains the elements carbon and oxygen.
Vitamin C is water soluble, and the body does not store it. To maintain adequate levels of vitamin C, humans need a daily intake of food that contains it.
Vitamin C plays an important role in a number of bodily functions including the production of collagen, L-carnitine, and some neurotransmitters. It helps metabolize proteins and its antioxidant activity may reduce the risk of some cancers.
Collagen, which vitamin C helps produce, is the main component of connective tissue and the most abundant protein in mammals. Between 1 and 2% of muscle tissue is collagen. It is a vital component in fibrous tissues such as:
- the gut
- blood vessels
Rebound scurvy can happen if a person takes very high doses of vitamin C and then discontinues it quickly.
Wound healing, infections, and tuberculosis
In 1982, researchers concluded that wounds, cuts, and grazes may heal faster in people with a higher intake of vitamin C than is usually available from their food. This may be because vitamin C contributes to collagen production.
The role of vitamin C as an antioxidant also helps repair tissue and reduce damage from inflammation and oxidation.
People with adequate levels of vitamin C are thought to be better able to fight off infections compared to people with vitamin C deficiency.
Vitamin C may also help prevent acute respiratory infections, especially in people with malnutrition and those who are physically stressed.
Researchers have also found that vitamin C can kill drug-resistant tuberculosis (TB) bacteria in a laboratory culture. A study published in 2013 suggests that adding vitamin C to TB drugs could shorten therapy.
Vitamin C and cancer therapy
Vitamin C may help in treating cancer. As an antioxidant, it protects the body against oxidative stress and helps prevent the oxidation of other molecules. It appears to regenerate other antioxidants in the body, too.
Oxidation reactions produce free radicals. Free radicals can start chain reactions that damage cells.
High doses of vitamin C have been found to reduce the speed of growth of some types of cancerous tissue. Researchers have proposed using vitamin C in cancer patients whose treatment options are limited.
More studies are needed to understand which cancers could be affected by vitamin C and which other effective treatments can be used in conjunction with vitamin C, as well as the long-term effects of this approach.
Some scientists have disputed the use of vitamin C in cancer treatment.
The National Cancer Institute report several studies that used high dose vitamin C intravenously with few side effects.
A number of doctors support it and are already using it in treatment.
"Research currently underway has shown that high concentrations of vitamin C can stop the growth, or even kill a wide range of cancer cells. Only intravenous administration of vitamin C can deliver the high doses found to be effective against cancer."
Dr. Ronald Hoffman
The United States Food and Drug Administration (FDA) has not yet approved the use of intravenous vitamin C in treatment of cancer patients, including those undergoing chemotherapy and radiation therapy, and it is not recognized as a treatment.
Other benefits of Vitamin C may include the following:
- Cardiovascular health: Vitamin C may widen the blood vessels, and this could help protect against heart disease and hypertension, or high blood pressure.
- Cholesterol levels: These were found to be lower in individuals with adequate levels of vitamin C.
- Cataracts: Vitamin C may help lower the risk of cataracts as well as of age-related macular degeneration.
- Diabetes: Patients are less likely to experience deterioration of the kidneys, eyes, and nerves if they eat plenty of fruit and vegetables that are rich in vitamin C.
- Anemia: Vitamin C enhances the absorption of iron.
- Lead levels may be reduced if there is an adequate intake of vitamin C.
- Histamine: Histamine is a substance the immune system produces, resulting in inflammation and other problems. A 1992 study found lower blood levels of histamine in people who took 2 grams (g) of vitamin C per day.
- Seasickness: In a study of 70 people who took either 2 g of vitamin C or a placebo and then spent 20 minutes on a life raft in a wave pool, those who took the supplement had reduced levels of seasickness.
Can vitamin C treat the common cold?
Many people believe that vitamin C can cure a common cold, but research has not confirmed this. However, large doses of vitamin C may protect people who are exposed to severe physical activity and cold temperatures.
People with low vitamin C, because of smoking or older age, for example, may find supplements beneficial.
Adult males should consume 90 milligrams (mg) of vitamin C per day and females should consume 75 mg per day, according to the National Institutes of Health (NIH). During pregnancy, women should have 85 mg a day, and 120 mg while breastfeeding.
The FDA's recommended daily value (DV) for vitamin C is 90 mg.
The best sources of vitamin C are fresh fruit and vegetables. Heat and cooking in water can destroy some of the vitamin C content, so raw foods are best.
Foods containing vitamin C include:
- Half a cup of sweet, red pepper: 95 mg or around 106% of DV.
- One medium orange: 70 mg or around 78% percent of DV.
- Half a cup of fresh strawberries: 49 mg or around 54% of DV.
- Half a cup of spinach: 9 mg or 10% of DV.
Other good sources include citrus fruits, tomatoes, and potatoes.
In developed countries, most people get enough vitamin C, although some groups are more likely to lack this nutrient.
These groups include:
- smokers and passive smokers
- people with limited food variety
- infants who consume evaporated or boiled milk
- people with malabsorption and some chronic diseases
Smokers have lower levels of vitamin C than nonsmokers, partly because they have higher levels of oxidative stress. Smoking also causes inflammation and damage to the mucous membranes of the mouth, throat, and lungs.
Too much vitamin C is unlikely to cause a problem. However, a high intake of over 1,000 mg a day may mean that not all the vitamin C is absorbed in the intestine. This can lead to diarrhea and gastrointestinal discomfort.
People with hereditary hemochromatosis, an iron absorption disorder, should talk to their doctor before taking vitamin C supplements, as high vitamin C levels could lead to tissue damage.
The maximum recommended daily intake of vitamin C for adult males and females is 2,000 mg.