Vitamin C is a vitamin. Some animals can make their own vitamin C, but people must get this vitamin from food and other sources. Good sources of vitamin C are fresh fruits and vegetables, especially citrus fruits. Vitamin C can also be made in a laboratory.
Most experts recommend getting vitamin C from a diet high in fruits and vegetables rather than taking supplements. Fresh-squeezed orange juice or fresh-frozen concentrate is a better pick than ready-to-drink orange juice. The fresh juice contains more active vitamin C. Drink fresh-frozen orange juice within one week after reconstituting it for the most benefit. It you prefer ready-to-drink orange juice, buy it 3 to 4 weeks before the expiration date, and drink it within one week of opening.
Historically, vitamin C was used for preventing and treating scurvy. Scurvy is now relatively rare, but it was once common among sailors, pirates, and others who spent long periods of time onboard ships. When the voyages lasted longer than the supply of fruits and vegetables, the sailors began to suffer from vitamin C deficiency, which led to scurvy.
These days, vitamin C is used most often for preventing and treating the common cold. Some people use it for other infections including gum disease, acne and other skin infections, bronchitis, human immunodeficiency virus (HIV) disease, stomach ulcers caused by bacteria called Helicobacter pylori, tuberculosis, dysentery (an infection of the lower intestine), and skin infections that produce boils (furunculosis). It is also used for infections of the bladder and prostate.
Some people use vitamin C for depression, thinking problems, dementia, Alzheimer's disease, physical and mental stress, fatigue, and attention deficit-hyperactivity disorder (ADHD).
Other uses include increasing the absorption of iron from foods and correcting a protein imbalance in certain newborns (tyrosinemia).
There is some thought that vitamin C might help the heart and blood vessels. It is used for hardening of the arteries, preventing clots in veins and arteries, heart attack, stroke, high blood pressure, and high cholesterol.
Vitamin C is also used for glaucoma, preventing cataracts, preventing gallbladder disease, dental cavities (caries), constipation, Lyme disease, boosting the immune system, heat stroke, hay fever, asthma, bronchitis, cystic fibrosis, infertility, diabetes, chronic fatigue syndrome (CFS), autism, collagen disorders, arthritis and bursitis, back pain and disc swelling, cancer, and osteoporosis.
Additional uses include improving physical endurance and slowing aging, as well as counteracting the side effects of cortisone and related drugs, and aiding drug withdrawal in addiction.
Sometimes, people put vitamin C on their skin to protect it against the sun, pollutants, and other environmental hazards. Vitamin C is also applied to the skin to help with damage from radiation therapy.
Natural Medicines rates effectiveness based on scientific evidence according to the following scale: Effective, Likely Effective, Possibly Effective, Possibly Ineffective, Likely Ineffective, Ineffective, and Insufficient Evidence to Rate.
The Effectiveness ratings for Vitamin C are as follows:
Likely Effective for...
Possibly Effective for...
Possibly Ineffective for...
Insufficient Evidence to Rate Effectiveness for...
More evidence is needed to rate vitamin C for these uses.
Vitamin C is LIKELY SAFE for most people when taken by mouth in recommended doses, when applied to the skin, when injected into the muscle, and when injected intravenously (by IV) and appropriately. In some people, vitamin C might cause nausea, vomiting, heartburn, stomach cramps, headache, and other side effects. The chance of getting these side effects increases the more vitamin C you take. Amounts higher than 2000 mg daily are POSSIBLY UNSAFE and may cause a lot of side effects, including kidney stones and severe diarrhea. In people who have had a kidney stone, amounts greater than 1000 mg daily greatly increase the risk of kidney stone recurrence.
Pregnancy and breast-feeding: Vitamin C is LIKELY SAFE for pregnant or breast-feeding women when taken by mouth in amounts no greater than 2000 mg daily for women over 19 years-old, and 1800 mg daily for women 14 to 18 years-old, or when given intravenously (by IV) or intramuscularly and appropriately. Taking too much vitamin C during pregnancy can cause problems for the newborn baby. Vitamin C is POSSIBLY UNSAFE when taken by mouth in excessive amounts.
Infants and children: Vitamin C is LIKELY SAFE when taken by mouth appropriately. Vitamin C is POSSIBLY UNSAFE when taken by mouth in amounts higher than 400 mg daily for children 1 to 3 years, 650 mg daily for children 4 to 8 years, 1200 mg daily for children 9 to 13 years, and 1800 mg daily for adolescents 14 to 18 years.
Angioplasty, a heart procedure: Avoid taking supplements containing vitamin C or other antioxidant vitamins (beta-carotene, vitamin E) immediately before and following angioplasty without the supervision of a health care professional. These vitamins seem to interfere with proper healing.
Cancer: Cancerous cells collect high concentrations of vitamin C. Until more is known, only use high doses of vitamin C under the direction of your oncologist.
Diabetes: Vitamin C might raise blood sugar. In older women with diabetes, vitamin C in amounts greater than 300 mg per day increases the risk of death from heart disease. Do not take vitamin C in doses greater than those found in basic multivitamins.
Blood-iron disorders, including conditions called “thalassemia” and “hemochromatosis”: Vitamin C can increase iron absorption, which might make these conditions worse. Avoid large amounts of vitamin C.
Kidney stones, or a history of kidney stones: Large amounts of vitamin C can increase the chance of getting kidney stones. Do not take vitamin C in amounts greater than those found in basic multivitamins.
Heart attack: Vitamin C levels are reduced during a heart attack. However, low vitamin C has not been linked to an increased risk for heart attack.
A metabolic deficiency called “glucose-6-phosphate dehydrogenase” (G6PD) deficiency: Large amounts of vitamin C can cause red blood cells to break in people with this condition. Avoid excessive amounts of vitamin C.
Smoking and chewing tobacco: Smoking and chewing tobacco lowers vitamin C levels. Vitamin C intake in the diet should be increased in people who smoke or chew tobacco.
Interaction Rating = Minor Be watchful with this combination.
Talk with your health provider.
The body breaks down acetaminophen (Tylenol, others) to get rid of it. Large amounts of vitamin C can decrease how quickly the body breaks down acetaminophen. It is not clear exactly when or if this interaction is a big concern.
Interaction Rating = Moderate Be cautious with this combination.
Talk with your health provider.
Aluminum is found in most antacids. Vitamin C can increase how much aluminum the body absorbs. However, it is not clear if this interaction is a big concern. Take vitamin C two hours before or four hours after antacids.
Aspirin is removed by the body through the kidneys and in the urine. Some scientists have raised concern that vitamin C might decrease how the body removes aspirin and could potentially increase the amount of aspirin in the body. There is concern that this could increase the chance of aspirin-related side effects. However, some research suggests that this is not an important concern and that vitamin C does not interact in a meaningful way with aspirin. Some research actually suggests that taking vitamin C with buffered aspirin might decrease the stomach irritation caused by aspirin. More evidence is needed about this possible benefit.
Vitamin C might decrease how quickly the body gets rid of choline magnesium trisalicylate (Trilisate). It is not clear if this interaction is a big concern.
The body breaks down estrogens to get rid of them. Vitamin C might decrease how quickly the body gets rid of estrogens. Taking vitamin C along with estrogens might increase the effects and side effects of estrogens.
Large amounts of vitamin C might decrease how much fluphenazine (Prolixin) is in the body. Taking vitamin C along with fluphenazine (Prolixin) might decrease the effectiveness of fluphenazine (Prolixin).
Vitamin C is an antioxidant. There is some concern that antioxidants might decrease the effectiveness of some medications used for cancers. But it is too soon to know if this interaction occurs.
Taking large doses of vitamin C might reduce how much of some medications used for HIV/AIDS stays in the body. This could decrease the effectiveness of some medications used for HIV/AIDS.
Some of these medications used for HIV/AIDS include amprenavir (Agenerase), nelfinavir (Viracept), ritonavir (Norvir), and saquinavir (Fortovase, Invirase).
Taking vitamin C, beta-carotene, selenium, and vitamin E together might decrease the effectiveness of some medications used for lowering cholesterol. It is not known if vitamin C alone decreases the effectiveness of some medications used for lowering cholesterol.
Some medications used for lowering cholesterol include atorvastatin (Lipitor), fluvastatin (Lescol), lovastatin (Mevacor), and pravastatin (Pravachol).
Taking vitamin C along with vitamin E, beta-carotene, and selenium might decrease some of the helpful effects of niacin. Niacin can increase the good cholesterol. Taking vitamin C along with these other vitamins might decrease the effectiveness of niacin for increasing good cholesterol.
Vitamin C is taken up by cells. Taking nicardipine (Cardene) along with vitamin C might decrease how much vitamin C is taken in by cells. The significance of this interaction is not clear.
Vitamin C is taken up by cells. Taking nifedipine (Adalat, Procardia) along with vitamin C might decrease how much vitamin C is taken in by cells. The significance of this interaction is not clear.
Taking vitamin C with pentobarbital might increase the sedative effects of pentobarbital.
Vitamin C might decrease how quickly the body gets rid of salsalate (Disalcid). Taking vitamin C along with salsalate (Disalcid) might cause too much salsalate (Disalcid) in the body, and increase the effects and side effects of salsalate.
Warfarin (Coumadin) is used to slow blood clotting. Large amounts of vitamin C might decrease the effectiveness of warfarin (Coumadin). Decreasing the effectiveness of warfarin (Coumadin) might increase the risk of clotting. Be sure to have your blood checked regularly. The dose of your warfarin (Coumadin) might need to be changed.
Acerola contains high levels of vitamin C. Don't take large amounts of acerola along with vitamin C. This might give you too much vitamin C. Adults should not take more than 2000 mg vitamin C per day.
Cherokee rosehip contains high levels of vitamin C. Don't take large amounts of Cherokee rosehip along with vitamin C. This might give you too much vitamin C. Adults should not take more than 2000 mg vitamin C per day.
There is some information that suggests that vitamin C increases chromium absorption. Don't take large doses of chromium and vitamin C together. It isn't known whether separating the doses by several hours avoids this interaction.
High doses of vitamin C (1500 mg daily) can decrease copper levels in the blood in young men. Researchers aren't sure why this happens, but it may be that the acid in vitamin C converts copper to a form that doesn't pass easily from food in the intestine to the bloodstream. Or it may be that vitamin C somehow causes the body to use up copper in the blood. This interaction probably isn't important except in people whose dietary levels of copper is low.
These is early evidence that people with high blood pressure who take both vitamin C 500 mg/day plus grape seed polyphenols 1000 mg/day have significantly increased blood pressure. Researchers aren't sure why this happens.
Vitamin C increases the absorption of iron when taken at the same time. Taking a vitamin C supplement to improve absorption of iron from the diet or from supplements probably isn't necessary for most people, especially if their diet contains plenty of vitamin C.
Niacin can increase good cholesterol levels. Taking vitamin C along with selenium, beta-carotene, and vitamin E might decrease the effects of niacin on good cholesterol levels. It is not known if vitamin C alone decreases the effects of niacin on good cholesterol levels.
Rosehip contains high levels of vitamin C. Don't take large amounts of rosehip along with vitamin C. This might give you too much vitamin C. Adults should not take more than 2000 mg vitamin C per day.
Early research suggests that vitamin C supplements can destroy vitamin B12 that comes from the diet. However, other ingredients in food, such as iron and nitrates, might counteract this effect. Researchers aren't sure how important this interaction is, but it can likely be avoided if vitamin C supplements are taken at least 2 hours after meals.
The following doses have been studied in scientific research:
The daily recommended dietary allowances (RDAs) are: Infants 0 to 12 months, human milk content (older recommendations specified 30-35 mg); Children 1 to 3 years, 15 mg; Children 4 to 8 years, 25 mg; Children 9 to 13 years, 45 mg; Adolescents 14 to 18 years, 75 mg for boys and 65 mg for girls; Adults age 19 and greater, 90 mg for men and 75 mg for women; Pregnancy and Lactation: age 18 or younger, 115 mg; ages 19 to 50 years 120 mg. People who use tobacco should take an additional 35 mg per day.
Do not take more than the following amounts of vitamin C: 400 mg per day for children ages 1 to 3 years, 650 mg per day for children 4 to 8 years, 1200 mg per day for children 9 to 13 years, and 1800 mg per day for adolescents and pregnant and breast-feeding women 14 to 18 years, and 2000 mg per day for adults and pregnant and lactating women.
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