Supplement Guide: Vitamin C
Are you getting enough C? Here's what you need to know
Where it comes from: Vitamin C—or ascorbic acid—is an essential nutrient. It protects the body against oxidative stress (thanks to antioxidant properties) and aids in tissue repair and helps bones grow and repair themselves. Dietary sources include fruits and vegetables, particularly citrus fruits such as oranges. It’s also popular in supplement form.
What it’ll do for you: Vitamin C helps produce collagen, a connective tissue that holds muscles, bones and other tissues together. It protects you from bruising by keeping capillary walls and blood vessels firm. It helps your body absorb iron and folate from plant food sources. It keeps your gums healthy, helps heal cuts and wounds and works as an antioxidant to inhibit damage to body cells. But the most touted benefit of vitamin C is that it protects you from infection by stimulating the formation of antibodies and so, boosting immunity.
“Vitamin C has developed celebrity status with claims that it can prevent or cure the common cold,” says Sari Greaves, RD spokesperson for the American Dietetic Association & Nutrition Director at Step Ahead Weight Loss Center in Bedminster, NJ. “Although those claims have been overblown, an adequate intake of vitamin C does play an important role in fighting infection.”
In 2004, a group of Australian researchers examined 29 prior studies involving 11,077 study participants. They found a consistent benefit in adults: a reduction in cold duration of eight percent. However for the most part, vitamin C supplements failed to reduce the incidence of colds. (Worth noting: Extreme athletes exercising in extreme cold have been proven to benefit from the cold-protecting properties of vitamin C.) So orange juice may not actually be the magic cure for your sniffles.
“For colds, extra vitamin C may have a mild antihistamine effect, perhaps shortening the duration of a cold and making the symptoms more mild,” says Greaves. “However, scientific evidence does not justify taking large doses of vitamin C regularly to boost immunity. So stick to the recommended dosage and replenish daily—since vitamin C is not stored in your body, make sure to habitually consume vitamin C-rich food or beverages.”
Suggested intake: The Recommended Dietary Allowance (RDA) for males is 90 mg of vitamin C daily. “If you smoke, you need 35 mg more of vitamin C daily to counteract the oxidative damage from nicotine,” Greaves adds.
How should you reach that dosage? Eat your fruits and vegetables! “Vitamin C mainly comes from plant sources,” says Greaves. All citrus fruits, including grapefruits, oranges and tangerines are good sources. Berries, melons, peppers, many dark green, leafy vegetables, potatoes and tomatoes also supply significant amounts. Greaves continues: “It’s more beneficial to get vitamin C from whole foods, which offer a goldmine of nutrients, versus taking a supplement, which just gives you an isolated dose. To help you navigate your supermarket’s produce section, Greaves recommends this helpful chart:
- 1/2 cup red bell pepper = 140 mg
- 1 medium guava = 125 mg
- 1/2 cup orange juice, from frozen concentrate = 75 mg
- 1 medium orange = 70 mg
- 1/2 cup green bell pepper = 60 mg
- 1/2 cup boiled broccoli = 50 mg
- 1/2 cup strawberries = 50 mg
- 1/2 white grapefruit = 50 mg
- 3/4 cup tomato juice = 35 mg
- 1/2 cup cantaloupe = 30 mg
- Medium baked potato, with skin = 20 mg
- 1 medium tomato = 15 mg
If you don’t get enough vitamin C, a severe deficiency can eventually lead to scurvy, a disease (popularized by pirates!) that causes loose teeth, excessive bleeding and swollen gums. Scurvy is rare in the United States because vitamin C-rich foods are widely available. Also, if you’re suffering from a lack of vitamin C, it’s possible that wounds may not heal properly.
Associated risks/scrutiny: Because vitamin C is water-soluble, your body excretes the excess in urine. But Greaves warns: Very large doses may cause kidney stones or diarrhea, and for those with iron overload (hemachromatosis), excessive vitamin C can make the problem worse. High amounts of Vitamin C can also mask the results of tests for diabetes. A tolerable upper intake level for vitamin C has been set at 2,000 mg daily for adults.