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vitamin C
   
What Is It?
Health Benefits
Forms
Recommended Intake
If You Get Too Little
If You Get Too Much
General Dosage Information
Guidelines for Use
General Interaction
Cautions
Evidence Based Rating Scale
References


What Is It?

In the eighteenth century, seasoned sailors found that by sucking on limes they could avoid scurvy, a debilitating disease that often developed during long voyages when fresh fruits and vegetables were scarce. When the lemon's key nutrient was formally identified in 1928, it was named ascorbic acid for its anti-scurvy, or antiscorbutic, action. Today ascorbic acid is widely known as vitamin C.

Health Benefits

The health benefits of vitamin C are abundant and varied, but it's probably best known as a cell protector, immunity booster, and powerful antioxidant. The body's ligaments, tendons, and collagen (a protein found in connective tissues) rely on the presence of vitamin C to stay strong and healthy. Like all antioxidants, vitamin C counters the effects of cell-damaging molecules called free radicals. As an added benefit, it even helps the body recycle other antioxidants. For certain conditions, vitamin C is best taken with other antioxidants, such as vitamin E, flavonoids, and carotenoids.

Specifically, vitamin C may help to:

Lessen the severity and duration of colds and flu. Taking vitamin C at the first sign of a cold or the flu may keep the illness from fully developing, and you'll probably recover faster. (1) In a 1995 review of studies investigating the effect of vitamin C on colds, researchers concluded that doses of 1,000 to 6,000 mg a day at the onset of symptoms reduced a cold's duration by 21%, and shortened its duration by one day on average. Taking vitamin C doesn't prevent colds, however. (2)

 

Speed wound healing and minimize the effects of bruising. Vitamin C helps the body to repair and maintain itself by reinforcing cell walls and helping to strengthen tiny blood vessels called capillaries. It further accelerates healing by inhibiting inflammation.

 

Keep gums strong and healthy. When taken daily, vitamin C protects gum tissue against cell damage and speeds healing in this delicate area. It's often taken with flavonoids for this purpose. Brushing the gums with vitamin C powder can also minimize inflammation and bleeding. (3)

 

Increase resistance to heart disease (and angina) by improving cholesterol levels. Several studies have linked the presence of low levels of vitamin C to a greater risk of angina and heart attacks in people with existing heart disease. (4-8) Research also indicates that, when taken with vitamin E, vitamin C helps protect LDL ("bad") cholesterol from oxidation, thus preventing plaque buildup in coronary arteries. (9) Vitamin C may also boost blood levels of HDL ("good") cholesterol; studies are ongoing to provide definitive evidence of this action.

 

Prevent certain cancers. As a powerful antioxidant, vitamin C may help to fight cancer by protecting healthy cells from free-radical damage and inhibiting the proliferation of cancerous cells. (10, 11) Specifically, recent studies have shown that the vitamin may help stave off cancers of the stomach and esophagus by blocking the conversion of nitrates and nitrites into cancer-causing compounds. (12, 13) Debate over the value of vitamin C for cancer treatment and prevention is fierce, however, with some studies finding no benefit—or even drawbacks—from vitamin C supplementation, while others report prolonged survival in cancer patients, especially when it's taken along with vitamin E.

 

Protect against cataracts. Vitamin C may keep the lens of the eye from being damaged by cigarette smoke and ultraviolet (UV) light, both types of exposure linked to cataract formation. One study showed that women who took vitamin C supplements for 10 years or more had a 77% lower risk of "lens opacities," the beginning stage of cataracts, than women who didn't use supplements. (14)

 

Relieve allergies, eczema, sinusitis, and asthma. Vitamin C is a natural antihistamine capable of blocking the effect of inflammatory substances some people produce in response to allergens such as pollen and pet dander. (15, 16) Allergies are often an underlying cause of sinusitis and may also trigger the intensely itchy rashes associated with eczema. Vitamin C is frequently recommended with other antioxidants such as flavonoids for sinusitis. Numerous studies have shown that vitamin C helps prevent or improve asthmatic symptoms as well; asthma sufferers are often deficient in this and other vitamins. Vitamin C has also been shown to help exercise-induced asthma attacks, in some cases thwarting an attack if taken in an adequate dose right before a workout. (17) Adults with exercise-induced asthma may want to experiment with doses from 500 mg to 5000 mg.

 

Prevent migraines. Taken along with pantothenic acid, vitamin C boosts the production of hormones that help the body deal with the adverse effects of stress-induced migraines.

 

Improve memory. As an antioxidant, vitamin C plays a key role in maintaining healthy nerve cells, and is often taken in combination with vitamin E, mixed carotenoids, ginkgo biloba, and coenzyme Q10 to help prevent memory loss. Several observational studies and one clinical controlled study have found that vitamin C may be beneficial in preventing the development of Alzheimer dementia. (18)

 

Fight chronic fatigue syndrome. Vitamin C taken with mixed carotenoids helps strengthen a weakened immune system, believed by many to be a factor in this disabling disorder. (19)

 

Control gallstone formation. Sometimes gallstones develop when bile contains high concentrations of cholesterol. Vitamin C may help to lower the risk of this occurring by reducing bile cholesterol levels. (20)

 

Combat the effects of aging and extend life. Used in combination with other antioxidants, such as vitamin E and flavonoids, vitamin C may combat the deteriorative effects of aging (such as wrinkles) caused by free-radical damage. (21) It may also help you live longer. In one study, men who took more than 300 mg of vitamin C a day (from food and supplements) lived longer than men who consumed less than 50 mg a day.

Note: Vitamin C's immune-boosting and antioxidant properties make it useful for many other disorders. For information on these additional ailments, see our Dosage Recommendations Chart for Vitamin C.

Forms

  • tablet
  • powder
  • liquid
  • capsule

Recommended Intake

The RDA for vitamin C for nonsmoking men and women is 60 mg a day (for smokers it's 100 mg). Recently experts have strongly suggested increasing the RDA to between 100 and 200 mg a day for all adults, and many recommend getting much more of this vitamin to maximize its health benefits.

If You Get Too Little

The chances of getting scurvy today are all but nonexistent, because just 10 mg of vitamin C a day prevents this disease. Less than 50 mg a day, however, can result in an increased risk of heart attack, cataracts, and a reduced life span.

If You Get Too Much

Because vitamin C is water-soluble—what the body cannot use, it eliminates in the urine and feces in about 12 hours—it's hard to get too much. But while many people are able to tolerate high doses of vitamin C (as much as 6,000 mg a day) with no ill effects, others may suffer from mouth ulcers, diarrhea, gas, and bloating at doses above 2,000 mg; these problems subside when the dose is reduced.

General Dosage Information

Special tip: Consider taking vitamin C as part of an antioxidant formula. It works best in concert with other antioxidants, especially vitamin E and flavonoids. The flavonoids, sometimes labeled as bioflavonoids, also enhance the effectiveness of vitamin C.

For general health: Make sure you get 500 mg a day through foods and supplements.

 

For the treatment of various diseases: Depending on the ailment, 1,000 to 6,000 mg may be appropriate.

 

Be sure to check out our Dosage Recommendations Chart for Vitamin C, which lists therapeutic dosages for specific ailments at a glance.

Guidelines for Use

  • Your body can't use more than 1,000 mg of vitamin C in any given dose. If you need to take a larger amount, split it into two or three doses spread throughout the day.
  • Vitamin C can be taken with or without food, as you prefer.
  • When shopping for vitamin C, don't waste money on specialized products—esterified C, time-released C, vitamin C with rose hips. There's no evidence that these are more efficiently absorbed than simple ascorbic acid.

General Interaction

  • Large doses of vitamin C may interfere with the body's absorption of copper and selenium; be sure to get enough of these minerals (copper, about 3 mg; selenium, about 100 mcg) through food or supplements.

Cautions

  • Large doses of vitamin C may cause a false positive result for glucose in the urine.
  • If you have hemochromatosis, a genetic tendency to store excess iron (vitamin C enhances iron absorption), don't take more than 500 mg of vitamin C a day.
  • Vitamin C can distort the accuracy of medical tests for colon cancer and hemoglobin levels. Let your doctor know if you're taking vitamin C supplements.

Evidence Based Rating Scale

The Evidence Based Rating Scale is a tool that helps consumers translate the findings of medical research studies with what our clinical advisors have found to be efficacious in their personal practice. This tool is meant to simplify which supplements and therapies demonstrate promise in the treatment of certain conditions. This scale does not take into account any possible interactions with any medication/ condition/ or therapy you may be currently undertaking. It is therefore advisable to ask your doctor before starting any new treatment regimen.

 

Condition

Rating

Explanation

Allergies

 

 

Numerous studies have shown efficacy.

 

 

 

 

Anti-aging

 

 

 

 

 

Date Published: 04/19/2005
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