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Vitamin C (Ascorbic acid)


What is it?

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.

How effective is it?

Natural Medicines Comprehensive Database 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 (ASCORBIC ACID) are as follows:

Effective for...

  • Treatment and prevention of vitamin C deficiency, including a condition called “scurvy.”

Likely effective for...

  • Improving the way the body absorbs iron.
  • Treating a disease called tyrosinemia in newborns when given as an injection.

Possibly effective for...

  • Wrinkled skin. Skin creams containing vitamin C or vitamin C in combination with acetyl tyrosine, zinc sulfate, sodium hyaluronate, and bioflavonoids (Cellex-C High Potency Serum) seem to improve wrinkles in facial skin aged by sun exposure.
  • Reducing the risk of certain cancers of the mouth and breast. This only works when fresh fruits and vegetables high in vitamin C are eaten, not with vitamin C supplements.
  • Treating the common cold. There is a lot of controversy about the effectiveness of vitamin C for treating the common cold. However, the majority of evidence shows that taking high doses of vitamin C might shorten the course of the cold by 1 to 1.5 days in some patients. But it is not effective for preventing the common cold.
  • Lowering high blood pressure. Taking vitamin C along with conventional high blood pressure medications appears to decrease systolic blood pressure (the top number in a blood pressure reading) by a small amount, but does not seem to decrease diastolic pressure (the bottom number). Taking vitamin C supplements alone, though, doesn’t seem to affect blood pressure.
  • Preventing sunburn. Taking vitamin C along with vitamin E seems to prevent sunburn. But taking vitamin C alone doesn’t prevent sunburn.
  • Reducing the risk of gallbladder disease. There is some evidence that taking vitamin C might help to prevent gallbladder disease in women. But vitamin C doesn’t seem to have this effect in men.
  • Slowing the worsening of osteoarthritis. Obtaining vitamin C from dietary sources seems to prevent cartilage loss and worsening of symptoms in people with osteoarthritis.
  • Treating an eye disease called AMD (age-related macular degeneration) when used with other medicines. Taking vitamin C in combination with zinc, vitamin E, and beta-carotene daily seems to help prevent vision loss or slow worsening of AMD in patients with advanced AMD. There isn't enough evidence to know if this combination helps people with less advanced macular disease or prevents AMD. Using vitamin C with other antioxidants, but without zinc, doesn't seem to have any effect on AMD.
  • Decreasing protein in the urine of people with type 2 diabetes (albuminuria). This might help to lower the risk of developing serious kidney disease.
  • Redness (erythema) after cosmetic skin procedures. There is some evidence that a particular vitamin C skin cream can decrease the amount of redness and the time it lasts following laser resurfacing for scar and wrinkle removal.
  • Decreasing lung infections caused by heavy exercise. Using vitamin C in amounts of 600 mg to 1 gram per day before heavy physical exercise, such as a marathon, might prevent upper respiratory infections that sometimes follow heavy exercise.
  • Treating ulcers in the stomach caused by bacteria called H. pylori. Taking vitamin C seems to decrease some of the side effects caused by treatment. After H. pylori bacteria are killed, vitamin C appears to decrease the occurrence of precancerous changes in stomach tissue.
  • Helping medicines used for chest pain, such as nitroglycerin, to work longer.
  • Reducing the risk in women of a circulatory system disorder called peripheral arterial disease.
  • Preventing “hardening of the arteries” (atherosclerosis).
  • Preventing kidney problems related to contrast media used during a diagnostic test called angiography.
  • Reducing human immunodeficiency virus (HIV) transmission by mothers to their newborns when taken with vitamins B and E.
  • Reducing complications after a broken wrist called complex regional pain syndrome, or reflex sympathetic dystrophy.
  • Reducing lead in the blood by eating foods high in vitamin C.
  • Reducing complications of a high-risk pregnancy (pre-eclampsia).
  • Improving physical performance and strength in the elderly.

Possibly ineffective for...

  • Preventing the common cold.
  • Reducing the risk of stroke.
  • Reducing the risk for Alzheimer's disease and other brain diseases that may cause intellectual loss.
  • Preventing eye disease associated with a medicine called interferon.
  • Treating bronchitis.
  • Reducing skin problems in people being treated for cancer with radiation.
  • Preventing pancreatic cancer.
  • Preventing prostate cancer.
  • Preventing type 2 diabetes.

Insufficient evidence to rate effectiveness for...

  • Hay fever (Allergic rhinitis). There is conflicting evidence about the effects of vitamin C on symptoms of hay fever. Taking vitamin C doesn’t seem to prevent hay fever.
  • Cataracts. There is conflicting information about the use of vitamin C to prevent cataracts. Vitamin C plus vitamin E and beta-carotene doesn't seem to have any significant effect on age-related loss of vision due to cataracts in well-nourished people who take the supplement long-term (for an average of 6.3 years). On the other hand, other research suggests that taking multivitamins that contain vitamin C for 10 years seems to prevent cataracts. Use of supplements for shorter periods doesn't appear to work.
  • Bladder cancer. Taking vitamin C does not seem to affect survival.
  • Lowering cholesterol. Taking vitamin C daily doesn’t seem to lower cholesterol in people whose cholesterol is not too high to start with. The effect of vitamin C on cholesterol levels in patients with high cholesterol is not known.
  • Cancer (Esophageal cancer, and colorectal cancer). Taking vitamin C in combination with beta-carotene plus vitamin E doesn't seem to prevent these types of cancer.
  • Stomach cancer. Not all research agrees on whether or not taking vitamin C supplements or getting extra vitamin C in the diet can prevent stomach cancer. Taking vitamin C supplements in combination with beta-carotene or beta-carotene plus vitamin E does not seem to reduce the risk of stomach cancer. But some evidence suggests that taking vitamin C alone might keep precancerous sores in the stomach from progressing to cancer in people at high risk for stomach cancer.
  • Mental stress. Limited evidence suggests that vitamin C might reduce blood pressure and symptoms during times of mental distress.
  • Ovarian cancer. Dietary vitamin C does not seem to affect the risk of getting ovarian cancer.
  • Kidney disease.
  • Liver disease.
  • Cystic fibrosis.
  • Infertility.
  • Diabetes.
  • Heart disease.
  • Attention deficit-hyperactivity disorder (ADHD).
  • Lyme disease.
  • Chronic fatigue syndrome (CFS).
  • Treating and preventing sun-damaged skin when vitamin C is put on the skin.
  • Wounds.
  • Pressure sores.
  • Tuberculosis.
  • Dental cavities.
  • Constipation.
  • Acne.
  • Other conditions.
More evidence is needed to rate vitamin C for these uses.

How does it work?

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Vitamin C is required for the proper development and function of many parts of the body. It also plays an important role in maintaining proper immune function.

Are there safety concerns?

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Vitamin C is LIKELY SAFE for most people when taken by mouth in recommended doses or when applied to the skin. 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 per day 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 per day greatly increase the risk of kidney stone recurrence.

Special precautions & warnings:

Pregnancy and breast-feeding: Vitamin C is LIKELY SAFE for pregnant or breast-feeding women when taken in the recommended amount of 120 mg per day. Taking too much vitamin C during pregnancy can cause problems for the newborn baby.

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.

A metabolic deficiency called “glucose-6-phosphate dehydrogenase deficiency” (G6PDD): Large amounts of vitamin C can cause red blood cells to break in people with this condition. Avoid excessive amounts of vitamin C.

Sickle cell disease: Vitamin C might make this condition worse. Avoid using large amounts of vitamin C.

Are there interactions with medications?

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Moderate

Be cautious with this combination.

Aluminum
Aluminum is found in most antacids. Vitamin C can increase how much aluminum the body absorbs. But it isn't clear if this interaction is a big concern. Take vitamin C two hours before or four hours after antacids.

Estrogens
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.

Fluphenazine (Prolixin)
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).

Medications for cancer (Chemotherapy)
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.

Medications used for HIV/AIDS (Protease Inhibitors)
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).

Medications used for lowering cholesterol (Statins)
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).

Niacin
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.

Warfarin (Coumadin)
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.

Minor

Be watchful with this combination.

Acetaminophen (Tylenol, others)
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.

Aspirin
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.

Choline Magnesium Trisalicylate (Trilisate)
Vitamin C might decrease how quickly the body gets rid of choline magnesium trisalicylate (Trilisate). But it is not clear if this interaction is a big concern.

Nicardipine (Cardene)
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.

Nifedipine
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.

Salsalate (Disalcid)
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.

Are there interactions with herbs and supplements?

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Acerola
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
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.

Chromium
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.

Copper
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.

Grape
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.

Iron
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.

Rosehip
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.

Vitamin B12
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.

Are there interactions with foods?

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There are no known interactions with foods.

What dose is used?

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The following doses have been studied in scientific research:

BY MOUTH:
  • For scurvy: 100-250 mg once or twice daily for several days.
  • For treating the common cold: 1-3 grams daily.
  • For preventing kidney damage related to contrast media used during diagnostic tests: vitamin C 3 grams is given before coronary angiography and then 2 grams is given after the procedure in the evening and again the following morning.
  • For slowing progression of hardening of the arteries: slow-release vitamin C 250 mg in combination with 91 mg (136 IU) of vitamin E twice daily for up to 6 years.
  • For tyrosinemia in premature infants on high protein diets: 100 mg of vitamin C.
  • For reducing protein in the urine of patients with type 2 diabetes: vitamin C 1250 mg with vitamin E 680 IU daily for 4 weeks.
  • For preventing complex regional pain syndrome in patients with wrist fractures, vitamin C 500 mg daily for 50 days.
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.

APPLIED TO THE SKIN:
  • Most topical preparations used for aged or wrinkled skin are applied daily. Studies have used creams containing 5% to 10% vitamin C. In one study a specific vitamin C formulation (Cellex-C High Potency Serum) used 3 drops applied daily to areas of facial skin. Don’t apply vitamin C preparations to the eye or eyelids. Also avoid contact with hair or clothes. It can cause discoloration.

Other names

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Acide Ascorbique, Acide Cévitamique, Acide Iso-Ascorbique, Acide L-Ascorbique, Acido Ascorbico, Antiscorbutic Vitamin, Ascorbate, Ascorbate de Calcium, Ascorbate de Sodium, Ascorbic acid, Ascorbyl Palmitate, Calcium Ascorbate, Cevitamic Acid, Iso-Ascorbic Acid, L-Ascorbic Acid, Magnesium Ascorbate, Palmitate d'Ascorbyl, Selenium Ascorbate, Sodium Ascorbate, Vitamina C, Vitamine Antiscorbutique, Vitamine C.

Methodology

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To learn more about how this article was written, please see the Natural Medicines Comprehensive Database methodology.methodology (http://www.nlm.nih.gov/medlineplus/druginfo/natural/methodology.html).

References

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To see all references for the Vitamin C (Ascorbic acid) page, please go to http://www.nlm.nih.gov/medlineplus/druginfo/natural/1001.html.

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