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Your Vitamin C Megadose Is Basically Useless

NUTRITION

Schools are back in session, which means the common cold is not too far behind.

VIT-C

To avoid a cold or cut one short, you may be tempted to stock up on supplemental drink mix-ins like Emergen-C and Airborne for supposed cold-fighting ingredients like vitamin C or zinc. But do these unregulated powders and tablets actually work?

Unless you’re a marathon runner, skier or soldier in extremely cold temperatures, extra vitamin C probably isn’t going to keep you from getting sick. And children are most likely to benefit from zinc, but their parents? Not so much.

The basics
Vitamin C, or ascorbic acid, is an essential nutrient that helps the body’s immune system, improves the body’s absorption of iron, helps metabolize protein and regenerates antioxidants in the body. Too little of it will lead to scurvy, historically considered a sailor’s disease because of the lack of access to fresh fruits and vegetables on long voyages. Too much of it can result in diarrhea, nausea, kidney stones and excess iron absorption.

Like most vitamins, the best way to consume this nutrient is via food: citrus, tomatoes, strawberries and spinach are just a few of the foods that are rich in vitamin C. Adult men should get at least 90 milligrams per day of vitamin C, while adult women should have at least 75 milligrams per day, according to the Institute of Medicine. The IOM also suggests an upper limit of 2,000 milligrams per day, lest people face the consequences listed above.

The IOM recommends that men and women get 11 milligrams and 8 milligrams, respectively, of zinc. It can be found in foods like oysters, red meat, poultry, beans, nuts and whole grains. Like vitamin C, consuming too much zinc exacts a toll on health; some nasal gels and sprays that contained zinc in caused anosmia (the inability to smell scents), and people who used too much denture cream containing zinc experienced copper deficiency and neurologic disease, notes the National Institutes for Health.

Most of us are not marathoners

Trials involving marathon runners, skiers and soldiers in sub-arctic environments found that these people were able to reduce their incidence of colds by 50 percent by taking anywhere from 250 milligrams to 1,000 milligrams per day of vitamin C, according to a 2007 Cochrane review of 30 placebo trials involving more than 11,000 total participants.

For everyone else, the results were a lot more modest. The review found that taking vitamin C preventively managed to reduce the length of a cold — but not prevent it — by eight percent for adults and 13.6 percent for children. That’s statistically significant, but probably doesn’t matter too much when a person is already in the throes of a cold. What’s more, if participants started taking vitamin C after the cold had already started, the nutrient didn’t have any effect on the symptoms or the length of the illness, concluded the National Institute of Health.

Research by the NIH also suggests that while levels of vitamin C rise in the body’s tissues after a person takes doses of 250 to 500 milligrams, any amount above that causes the body’s vitamin C levels to rise much more slowly — at least in healthy young men.

As with vitamin C, studies on zinc’s ability to curtail colds or lessen their severity is mixed. A 2011 review of 15 trials involving zinc found that if otherwise healthy people took zinc supplements within 24 hours of the onset of cold symptoms, they were able to cut the cold short and mitigate symptoms. It also found that taking zinc supplements preventively reduces the number of colds, level of school absenteeism and use of antibiotics in children. However, the review couldn’t recommend a dosage, formulation or even a duration that zinc supplements should be used.

Where the supplements stand

Like all dietary supplements, Emergen-C and Airborne did not have to pass safety and efficacy research before hitting the market. That’s not exactly heartening when you consider the tepid results of their active ingredients when it comes to cold prevention.

But the companies do seem to keep in mind the IOM’s recommended upper limits for vitamin C. Emergen-C, which has 1,000 milligrams of vitamin C per serving, changed their recommended servings to align with medical opinion.

“The directions on our packages have been changed from two to four packets per day to one to two packets per day as we are simply being more conservative with our recommendations,” a representative of Alacer Corp., Emergen-C’s parent company, told HuffPost.

Airborne, an effervescent tablet meant to be dissolved in water, also has 1,000 milligrams of vitamin C per serving.

But unless researchers can conduct experiments specifically testing Emergen-C or Airborne’s effectiveness, there’s no way to tell for sure if they work, or why, according to Howard Sesso, an epidemiologist and associate professor of medicine at Brigham and Women’s Hospital in Boston.

“It would be very difficult to know, even if it did work, is it because of Vitamin C, or is it because of Zinc?” said Sesso. “Is it because of something completely unrelated, or something that we don’t yet know about?”

Here’s what you should do instead

Sesso, a middle-aged man who eats well and exercises regularly, takes just one multivitamin a day. He says this option is probably appropriate for most people, as opposed to focusing on just one or two specific vitamins to avoid disease. While there certainly are special populations for which specific supplements are crucial — say, folic acid for pregnant women, to avoid birth defects — getting all your vitamins and minerals from a variety of healthy foods is the best way to approach nutritional health.

“Natural, food-based approach… is always more preferable,” said Sesso.

Sesso also noted that there are certainly more effective ways to avoid illness during cold season. Some tactics include washing your hands frequently, staying away from sick people and keeping surfaces in your home clean.

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