一天一片维生素可能弊大于利

医镜 · 发表于 2007-1-24 14:05:42

A vitamin a day may do more harm than good

ConsumerLab.com report finds unexpected nutrient levels, contamination

By Jacqueline Stenson
Contributing editor
MSNBC
Updated: 11:26 a.m. ET Jan. 19, 2007

If you're banking on a daily vitamin to make up for any deficiencies in your diet, you may be getting a whole lot more — or less — than you bargained for.

Of 21 brands of multivitamins on the market in the United States and Canada selected by ConsumerLab.com and tested by independent laboratories, just 10 met the stated claims on their labels or satisfied other quality standards.

Most worrisome, according to ConsumerLab.com president Dr. Tod Cooperman, is that one product, The Vitamin Shoppe Multivitamins Especially for Women, was contaminated with lead.

"I was definitely shocked by the amount of lead in [this] woman's product," he said. "We've never seen that much lead in a multivitamin before."

Other products contained more or less of a particular vitamin than listed on the label. And some did not dissolve in the correct amount of time, meaning they could potentially pass through the body without being fully absorbed.

"Half the products were fine, half were not," said Cooperman.

ConsumerLab.com is a Westchester, N.Y.-based company that independently evaluates hundreds of health and nutrition products and periodically publishes reviews. In the new report, released to MSNBC.com, the company purchased a selection of the popular multivitamins on the market as well as some smaller brands and sent them, without labels, to two independent laboratories to be tested.

On a positive note, several of the most popular multivitamins on the market did pass muster, said David Schardt, a senior nutritionist at the Center for Science in the Public Interest, a nonprofit consumer advocacy group in Washington, D.C.

These included Centrum Silver, Member's Mark Complete Multi (distributed by Sam's Club), One A Day Women's and Flintstones Complete.

"I think this confirms the advice often given: You're safer choosing a well-known brand sold by some company or store that you have confidence in," Schardt said. "There are no guarantees but that's your best bet."

Random vitamin testing isn't foolproof. For instance, because ConsumerLab.com tested several bottles from a particular lot number of each vitamin, it's not a given that products produced at a different time would have the exact same contents. But detectable problems are a red flag that there could be problems with a company's production process.

In the report, tests showed that The Vitamin Shoppe women's product contained 15.3 micrograms of lead per daily serving of two tablets.

This amount of lead is more than 10 times the amount permitted without a warning in California, the only state that regulates lead in supplements, Cooperman said. On average, most American adults are exposed to about 3 micrograms of lead through food, wine and other sources, he said, and while 15.3 micrograms of lead per day may not be immediately toxic, the mineral is stored in the body and could build up to dangerous levels with time.

"I would be concerned about a woman taking a multivitamin that contains 15.3 micrograms of lead per daily serving," said Judy Simon, a dietitian at the University of Washington Medical Center in Seattle. Among other effects, she said, lead can contribute to high blood pressure.

The same product also contained just 54 percent of the 200 milligrams of calcium stated on the label.

The analysis also showed that Hero Nutritionals Yummi Bears, a multivitamin for children, had 216 percent of the labeled amount of vitamin A in the retinol form, delivering 5,400 International Units (IU) in a daily serving. That's substantially more than the upper tolerable level set by the Institute of Medicine of 2,000 IU for kids ages 1 to 3 and 3,000 IU for those 4 to 8.

Because too much vitamin A can cause bone weakening and liver abnormalities, the Yummi Bears "could be potentially doing more harm than good," Cooperman said. "Vitamin A is one of those vitamins where you really don't want to get too much."

Schardt said the lead and vitamin A findings are worrisome because vitamins are generally taken every day, potentially building up to toxic levels and leading to problems down the line. In particular, he noted, women with high levels of lead in their bodies who become pregnant could pass on problems to a fetus.

David Morrison, vice president of scientific and regulatory affairs at The Vitamin Shoppe, said his company's products are all tested more than once, including screening for lead, and he questioned the new results. "It would be very surprising to me if this were actually true," he said.

Hero Nutritionals did not respond to calls seeking comment.

Steve Mister, president and CEO of the Council for Responsible Nutrition, a trade group in Washington, D.C., that represents supplement manufacturers, said that if the findings on lead and vitamin A are, in fact, accurate, "that is not acceptable for the industry."

But he also said that top manufacturers consistently produce quality products and that with 150 million Americans taking vitamins or other dietary supplements annually, few problems surface.

"If we had a serious issue of safety, we'd be hearing concerns from consumers in large numbers and we're not," he said.

The ConsumerLab.com report also found that some vitamins didn't break apart within the 30-minute standard set by the United States Pharmacopeia. Nature's Plus Especially Yours for women required more than an hour to disintegrate, while AARP Maturity Formula took 50 minutes.

These products "could potentially go through your body without releasing all the nutrients," Cooperman said.

Mark Kitchens, an AARP spokesperson, said the Maturity Formula undergoes routine testing, and that during testing in November "among the attributes tested was dissolution and it met FDA requirements." Still, "as precautionary measures to protect our members" AARP is pulling the product from the market and offering refunds to anyone who has purchased it, he said.

In other findings, Eniva VIBE, a multivitamin liquid sold in packets, had only 54 percent of the claimed vitamin A.

ConsumerLab.com also tested a vitamin marketed for dogs called Pet-Tabs Complete Daily Vitamin-Mineral Supplement for Dogs and found the product was contaminated with 1.4 micrograms of lead per tablet.

Whether most people — or dogs, for that matter — really need to take a multivitamin is a subject of debate.

Experts agree that prenatal vitamins are important for women who are pregnant or may become pregnant, and that people with very poor diets can benefit from nutrients in a pill.

Schardt says multivitamins offer everyone "an inexpensive insurance policy." But Cooperman and many dietitians note that it's better to get your nutrition from a well-balanced diet.

"In many cases, you don't need a multivitamin," Cooperman said.

© 2007 MSNBC Interactive

http://www.msnbc.msn.com/id/16655168/

账号		自动登录	找回密码
密码			注册