America’s favorite dietary supplements, multivitamins, modestly lowered the risk for cancer in healthy male doctors who took them for more than a decade, the first large study to test these pills has found.
The result is a surprise because many studies of individual vitamins have found they don’t help prevent chronic diseases and some have even caused problems.
In the new study, multivitamins cut the chance of developing cancer by 8%. That is less effective than a good diet, exercise and not smoking, each of which can lower cancer risk by 20% to 30%, cancer experts say.
Multivitamins also may have different results in women, younger men or people less healthy than those in this study.
“It’s a very mild effect and personally I’m not sure it’s significant enough to recommend to anyone” although it is promising, said Dr. Ernest Hawk, vice president of cancer prevention at the University of Texas MD Anderson Cancer Center and formerly of the National Cancer Institute.
“At least this doesn’t suggest a harm” as some previous studies on single vitamins have, he said.
Hawk reviewed the study for the American Association for Cancer Research, which is meeting in Anaheim, Calif., where the study was to be presented on Wednesday. It also was published online in the Journal of the American Medical Association.
About one-third of U.S. adults and as many as half of those over 50 take them. They are marketed as a kind of insurance policy against bad eating. Yet no government agency recommends their routine use “regardless of the quality of a person’s diet,” says a fact sheet from the federal Office of Dietary Supplements.
Some fads, such as the antioxidant craze over vitamins A and E and beta-carotene, backfired when studies found more health risk with those supplements, not less. Many of those were single vitamins in larger doses than the “100% of daily value” amounts that multivitamins typically contain.
Science on vitamins has been skimpy. Most studies have been observational — they look at groups of people who do and do not use vitamins, a method that can’t give firm conclusions.
Dr. J. Michael Gaziano, of Brigham and Women’s Hospital and VA Boston, led a stronger test. Nearly 15,000 male doctors who were 50 or older and free of cancer when the study started were given monthly packets of Centrum Silver or fake multivitamins without knowing which type they received.
After about 11 years, there were 2,669 new cancers, and some people had cancer more than once. For every 1,000 men per year in the study, there were 17 cancers among multivitamin users and more than 18 among those taking the placebo pills. That worked out to an 8% lower risk of developing cancer in the vitamin group.
Multivitamins made no difference in the risk of developing prostate cancer, which accounted for half of all cases. They lowered the risk of other cancers collectively by about 12%. There also was a trend toward fewer cancer deaths among multivitamin users, but the difference was so small it could have occurred by chance alone.
Side effects were fairly similar except for more rashes among vitamin users. The National Institutes of Health paid for most of the study. Pfizer Inc. supplied the pills and other companies supplied the packaging.
The main reason to take a multivitamin is to correct or prevent a deficiency, “but there may be a modest benefit in reducing the risk of cancer in older men,” Gaziano said.
Cancer experts said the results need to be confirmed by another study before recommending multivitamins to the public. These participants were healthier — only 4% smoked, for example.
For people who do want to take multivitamins, doctors suggest:
— Be aware that they are dietary supplements, which do not get the strict testing required of prescription medicines.
— Ask your doctor before taking any. Vitamin K can interfere with common heart medicines and blood thinners, and vitamins C and E can lower the effectiveness of some types of chemotherapy. For people having surgery, some vitamins affect bleeding and response to anesthesia.
— Current and former smokers should avoid multivitamins with lots of beta-carotene or vitamin A; two studies have tied them to increased risk of lung cancer.
Copyright 2012 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.
In lots of little ways, this AP piece exemplifies the difference between very good and outstanding health reporting. Compared with the solid effort from Reuters, the AP’s take was just a little more thorough in its evaluation of the evidence and its implications for readers. Some examples:
The AP did require about 100 more words to deliver these details, and we realize that space is always a concern. Sometimes it does take a little more space to thoroughly address all of our criteria.
Current evidence is unclear as to whether vitamin supplements help prevent chronic diseases, and they’ve been shown to cause harm in some cases. That’s why, with the exception of people suffering from a vitamin deficiency, most of us are advised to get our vitamins from food instead of supplements. The current consensus, however, is based on studies that typically used high doses of a single vitamin. The low-dose multivitamin used here doesn’t seem to cause the same problems seen in other research, and may even offer a benefit for men similar to those in this study. That’s good news, of course, but it’s hard to get too excited considering the very small size of the reduction, which is barely outside of the range that would be considered statistical noise. It’s the kind of finding that could easily be reversed when the next study comes around–and readers should be warned accordingly.
Not applicable. Most people know that multivitamins are inexpensive.
The story was very cautious in its framing of the results, quoting a researcher who called the effect “very mild” and who said he wasn’t sure it’s significant enough to recommend to anyone. The story also took the time to explain exactly what the benefit looked like in absolute terms: “After about 11 years, there were 2,669 new cancers, and some people had cancer more than once. For every 1,000 men per year in the study, there were 17 cancers among multivitamin users and more than 18 among those taking the placebo pills. That worked out to an 8% lower risk of developing cancer in the vitamin group.” The competing Reuters coverage didn’t provide these details.
The story states that side effects were similar between vitamin and placebo group participants, with the exception of their being more rashes among vitamin users. The story also touches on potential harms from dietary supplements in general (e.g. they are minimally regulated and not subject to strict testing for purity) and for specific groups (e.g. people on blood thinners or with cancer, whose vitamin use might interfere with their treatment).
The story provides a solid explanation of where this study fits in the hierarchy of vitamin research. It explains how the study differs from previous trials that looked at the effects of individual vitamins in higher doses. It also differentiates the new research from previous observational studies of vitamin users, which “can’t give firm conclusions.”
No disease-mongering. The story is clear that the results apply to older, relatively healthy men who don’t smoke.
We hear from an expert who wan’t involved with the study, and we receive a complete description of the study’s funding sources. The story notes that while NIH paid for most of the study, Pfizer supplied the pills. That’s a detail we didn’t hear about in the competing Reuters piece.
The story says that multivitamins are “less effective than a good diet, exercise and not smoking, each of which can lower cancer risk by 20% to 30%, cancer experts say.” We’ll call this good enough for a satisfactory, but we do quibble with the story’s broad assertions regarding the effectiveness of these lifestyle recommendations. With the exception of smoking cessation, which is certainly effective for preventing cancer, it’s never been conclusively proven that dietary changes or exercise can reduce cancer risk. In fact, recent research suggests that fruits and vegetables — long thought to be strong cancer fighters — actually have little or no effect on cancer risk. Obesity is emerging as the main diet-related culprit when it comes to cancer, something the story could have been more precise about.
The availability of multivitamins is not in question.
The story is clear about where this study stands in context with previous research.
It’s clear that this story wasn’t based on a press release.