Vitamin C

Other name(s):

antiscorbutic agent, ascorbic acid, calcium ascorbate, dehydroascorbic acid, sodium ascorbate

General description

Vitamin C is a water-soluble vitamin. That means it can dissolve in water. It’s found in many fruits and vegetables and is a popular supplement. Many people feel that large doses benefit the body. Vitamin C is important in the health of the connective tissues of the body. Some studies show that vitamin C may help reduce the symptoms and length of the common cold.

Vitamin C plays many roles in the chemistry of the human body. It’s needed to make collagen. This is a critical part of the body's connective tissue. It also helps increase the absorption of iron from the intestines. This is needed to make hemoglobin, the oxygen-carrying pigment inside of red blood cells.

Vitamin C is needed for many chemical reactions. The body uses vitamin C to make other important substances. These include:

• Carnitine

• Tyrosine

• Steroids made in the adrenal gland

• Neurotransmitters

Vitamin C is also a strong antioxidant. Antioxidants are thought to play a role in slowing the aging process. It may also reduce damage to the lining of blood vessels, and reduce the risk of some types of cancer. Mounting evidence shows that vitamin C has a role in all of these processes.

Medically valid uses

Before the discovery of vitamin C, scurvy affected people who had little access to fresh fruits and vegetables. Scurvy was common among sailors who were away at sea for months at a time. When it was found that eating limes could prevent scurvy, British sailors were nicknamed "Limeys." Later, vitamin C was discovered. It was used to prevent and treat scurvy.

Research suggests that taking vitamin C regularly may help lessen the symptoms of the common cold. It may also reduce how long the cold lasts. But vitamin C likely doesn’t prevent colds. Taking vitamin C only after the start of cold symptoms doesn't appear to help.

Unproven claims

Please note that this section reports on claims that have not yet been proven through studies.

Vitamin C is said to help prevent or cure gum disease (periodontitis). At this time, the evidence varies on if vitamin C helps prevent cancer.

Most studies don't show enough evidence that vitamin C supplements protect against heart and blood vessel disease.

Vitamin C may protect the body against some of the effects of pollution. It may also prevent blood clots and reduce bruising.

Recommended amounts

Vitamin C is measured in milligrams (mg). RDA is the Recommended Daily Allowance. ULs is Tolerable Upper Intake Level. Tablets and chewable tablets are the most common forms. It’s also available in:

• Time-release capsules

• Gummies

• Powder

• Lozenges

• Liquid

• Injections

People who smoke may need an extra 35 mg of vitamin C per day.

Vitamin C taken by mouth or injection is effective for curing scurvy. In adults, the treatment is 300 to 1,000 mg daily for one month. Symptoms should start to improve within 24 to 48 hours. You should be fully better within 7 days. Lower doses may be enough for vitamin C deficiency with no symptoms.

Vitamin C is sensitive to light and oxygen. Store supplements in light-resistant and air-tight containers. Store them at room temperature or in the refrigerator. But don't freeze them. Don’t store them in metal containers.

Many fruits and vegetables supply vitamin C. The following table shows a sample of sources.

Vitamin C easily changes or breaks down with handling, storing, or cooking. Fresh produce has the highest levels of vitamin C. If vegetables are wilted, the vitamin C levels will be largely reduced. Fresh potatoes have a high vitamin C content. But winter storage reduces the level to only 20% of the original content. Boiling reduces it even more.

High temperatures break down vitamin C more quickly in the presence of oxygen or light. Cooking fruits and vegetables destroys much of the vitamin C. Eat raw or lightly cooked fruits and vegetables to get the highest amount of vitamin C.

You may need vitamin C supplements if any of the below apply to you:

• You have a diet low in fresh fruits and vegetables

• You drink moderate to heavy amounts of alcohol

• Smoke or are exposed to secondhand smoke

• You use illegal drugs

• You work outdoors or do exercise outside in very cold weather

• You have a lot of emotional or physical stress

• Prolonged illness

• You had major surgery

• You have a hyperactive thyroid gland

• You don’t have enough stomach acid

• You have had part or all of the stomach removed (gastrectomy)

Women who are pregnant or breastfeeding may need to take supplements. Talk to your healthcare provider first.

Vitamin C deficiency can lead to scurvy. Scurvy causes increased bleeding of the gums, skin, muscles, and internal organs.

Other symptoms of vitamin C deficiency include:

• Slow healing of wounds

• Rough, cracked skin

• Changes in the bones

• Joint pain and fluid in the joints

• Enlargement of the hair follicles, with a buildup of skin at the base of the hair

• Anemia

• Fatigue

Side effects, toxicity, and interactions

There are no side effects linked with reasonable doses of vitamin C. Excess vitamin C comes out in the urine. Side effects from too much vitamin C may include:

• Stomach pain or cramping

• Nausea or vomiting

• Diarrhea

• Urinating more than normal

• Blood in your urine

If you’re prone to kidney stones, high doses of vitamin C may worsen kidney stones.

Some forms of vitamin C contain sulfites or tartrazine. Make sure your supplement doesn’t have these if you’re allergic to them.

Medicine interactions

If you take any of the following medicines, talk to your healthcare provider before taking vitamin C supplements:

• Acetaminophen or antacids that have aluminum. This includes aluminum hydroxide. Vitamin C may increase the side effects of these medicines.

• Aspirin. Vitamin C may cause aspirin to build up in your body, and aspirin may decrease the levels of vitamin C in your body.

• Barbiturates. These include phenobarbital, pentobarbital, and secobarbital. Vitamin C may keep these medicines from working as well as they should.

• Fluphenazine. Vitamin C may reduce the amount of this medicine in your body.

• Indinavir. Vitamin C may reduce the amount of this medicine in your body.

• Nicotine products, such as cigarettes. These may decrease the effects of vitamin C.

• Oral estrogens. These may decrease the effects of vitamin C in your body. Vitamin C may increase the levels of ethinyl estradiol in your body.

• Tetracycline antibiotics. These include doxycycline, minocycline, and tetracycline. They may keep vitamin C from working as well as it should in your body.

• Warfarin. Vitamin C may interfere with the blood-thinning effects of this medicine.

There is limited evidence that high-dose vitamin C may reduce side effects of levodopa. These include nausea or trouble with coordination.

High doses of vitamin C aren’t advised for people with kidney failure. Talk to your healthcare provider before taking vitamin C if you take medicines that may cause kidney problems.

Herbs and dietary supplements interactions

Vitamin C may increase the absorption of iron in your gastrointestinal tract. It may also increase the absorption of lutein vitamin supplements.

Large doses of vitamin C may interfere with the absorption and metabolism of vitamin B-12.

Large doses of vitamin C may interact with herbs and supplements that have hormonal, antibacterial, and blood-thinning (anticoagulant) activity.