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. 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 conditions, 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 or inflammation of the bladder and prostate, nerve pain, pregnancy-related complications.
Some people use vitamin C for depression, thinking problems, dementia, Alzheimer's disease, physical and mental stress, fatigue including chronic fatigue syndrome (CFS), autism, attention deficit-hyperactivity disorder (ADHD), schizophrenia, Lou Gehrig's disease, and Parkinson's disease. It is also used to treat or prevent toxicity caused by certain drugs or metals and to treat peptic ulcers, swine flu, sudden hearing loss, gout, and tetanus.
Other uses include increasing the absorption of iron from foods. Vitamin C is also used in combination with a drug called deferoxamine to increase removal of iron from the blood. Some people use iron to correct a protein imbalance in certain newborns (tyrosinemia). It is also used to prevent the transfer of HIV from mothers to babies during breastfeeding. Vitamin C is also used to help reduce the side effects of bowel preparation.
There is some thought that vitamin C might help the heart and blood vessels. It is used for heart disease, hardening of the arteries, preventing clots in veins and arteries, heart attack, stroke, high blood pressure, high cholesterol, irregular heartbeat after surgery, nitrite tolerance, or inadequate blood flow that causes blood to pool in the legs. It is also thought that vitamin C may increase the healing of burns, ulcers, fractures, and other wounds. Vitamin C is also used to prevent long-term pain after surgery or injury.
Vitamin C is also used for glaucoma, preventing cataracts, preventing gallbladder disease, dental cavities and plaque, constipation, Lyme disease, age-related vision loss, boosting the immune system, heat stroke, hay fever and other allergy-related conditions, asthma and exercise-induced asthma, bronchitis, cystic fibrosis, sickle cell disease, infertility, diabetes, collagen disorders, arthritis and other types of joint inflammation, back pain and disc swelling, cancer, and osteoporosis and other bone conditions.
Additional uses include improving physical endurance and slowing aging, as well as counteracting the side effects of cortisone and related drugs, aiding drug withdrawal in addiction, and reducing side effects of radiation therapy.
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.
Vitamin C is inhaled through the nose to treat hayfever.
How it works
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.
EffectiveVitamin C deficiency
Taking vitamin C by mouth or injecting as a shot prevents and treats vitamin C deficiency, including scurvy. Also, taking vitamin C can reverse problems associated with scurvy.
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 isLIKELY SAFEforpregnantor 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 isPOSSIBLY UNSAFEwhen 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.
Alcoholism: Alcohol intake can cause the body to excrete vitamin C in the urine. People who regularly use alcohol, especially those who have other illnesses, often have vitamin C deficiency. These people might need to be treated for a longer time than normal to restore vitamin C levels to normal.
Alzheimer's disease: Taking vitamin C along with vitamin E and alpha-lipoic acid might worsen mental function in people with Alzheimer's disease.
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.
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.
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.
Kidney transplant rejection: Long-term use of vitamin C in high doses before a kidney transplant may increase the risk of transplant rejection or delay how long it takes until the transplanted kidney works.
Schizophrenia: Taking vitamin C along with vitamin E might worsen psychosis in some people with schizophrenia when taken with antipsychotic drugs.
Sickle cell disease: Vitamin C might make this condition worse. Avoid using large 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.
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.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).Indinavir (Crixivan)
Indinavir (Crixivan) is a medication used for HIV/AIDS. Taking large amounts of vitamin C along with indinavir (Crixivan) might decrease how much of indinavir (Crixivan) stays in the body. It's not clear if this interaction is a big concern.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.Niacin
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.Pentobarbital
Taking vitamin C with pentobarbital might increase the sedative effects of pentobarbital.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.
MinorAcetaminophen (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). It is not clear if this interaction is a big concern.Nicardipine (Cardene)
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).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.