No evidence that Ester-C vitamin C protects against colds.

It’s winter, the season of colds and flu. So time for dietary supplement companies to promote their products as immunity-protectors. Even though there’s little evidence that they are.

Did you see the big display of Ester-C brand of vitamin C at Costco claiming the supplement provides 24-hour immune suppport? Ester-C is a fancy brand of vitamin C from manufacturer NBTY of Ronkonkoma, New York, that sells for about four times as much as plain vitamin C.

Let’s cut to the chase: NBTY has no evidence that people who take Ester-C are any less likely to get sick than people who don’t take Ester-C.

The company claims that the main benefit of Ester-C is its quick absorption and 24-hour retention in the immune system, which it calls “24-hour immune protection.”  It also touts Ester-C as the “better” vitamin C because “it’s gentle on the stomach.”

Ester-C vitamin C

All these claims stretch the truth.

Quick absorption.

In the company’s own study—a one-day experiment in 15 young men—regular vitamin C was absorbed just as fast into the bloodstream and remained there at the same level for just as long as Ester-C. The men took 1,000 mg of regular vitamin C or 1,000 mg of Ester-C or a placebo on separate mornings.

“24-hour immune protection”

By “immune support,” NBTY means merely the presence of vitamin C in white blood cells, not whether Ester-C actually prevents anyone from getting sick. In the company study, both regular vitamin C and Ester-C remained in the volunteers’ white blood cells for at least 24 hours.

But, starting at hour four, there was about 30 percent more vitamin C in the white blood cells of Ester-C takers than there was in the white blood cells of regular- C takers. And Ester-C levels remained higher for the rest of the 24 hours.

So, does 30 percent more Ester-C in white blood cells boost your immunity to disease? The researchers and the company can’t say. In fact, no one really knows.

Gentle on the stomach?

In the company’s study, people who took 1,000 mg a day of Ester-C for three days complained of heartburn or diarrhea just about as often as people who took the same amount of regular vitamin C. The researchers conceded that most people wouldn’t suffer any distress from either kind of vitamin C.

Do large amounts of any extra vitamin C help prevent illness? It may make a difference in people undergoing great physical exertion. In six studies of 642 marathon runners, skiers, and soldiers on subarctic exercises, those who took about 1,000 mg a day of vitamin C to prevent colds got sick only half as often as those who didn’t take C.

But what about most of us who are not under great physical stress? In 29 studies of more than 11,000 people, those who took about 1,000 mg a day of vitamin C had no fewer colds than those who didn’t take extra C. But if they were taking that much of the vitamin before getting sick and continued while they were sick, their seven-day colds were shorter by about half a day and milder than those who took a placebo.

Sources: Adv. Ther. 25: 995, 2008; Cochrane Database Syst. Rev. (3): cD000980, 2007; Adv. Ther. 23: 171, 2006.

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