Science can drive you to despair. Just when you’ve become comfortable on the vitamin supplement bandwagon, convinced that a one-a-day multi is the way to go, you hit a bump on the road. A pretty large one! The bump in this case comes in the form of a headline, as featured on the cover of The Lancet, one of the prime medical research journals in the world: “The prospect that vitamin pills may not only do no good but also kill their consumers is a scary speculation given the vast quantities that are used in certain communities.” Scary, indeed. What’s going on?
The study that prompted the editorial comment on the cover page and stunned the scientific community appeared in the October 2, 2004, issue of The Lancet. Researchers led by Goran Bjelakovic of the University of Nis (Serbia and Montenegro) were interested in determining whether antioxidant supplements reduced the risk of gastrointestinal cancers and mortality. Both the lay press and the scientific publications have been singing the praises of antioxidants for years. Free radicals, those rogue species that roam through our body, damaging essential molecules like DNA, can be swallowed up by antioxidants, they claimed. At least that’s what happened in the test tube. Furthermore, eating fruits and vegetables, which are loaded with the likes of beta-carotene, vitamin C, vitamin E, polyphenols, and selenium—all recognized antioxidants—is clearly associated with a reduced risk of cancer. So it certainly seemed reasonable to assume that supplemental antioxidants should be beneficial in preventing cancer, especially of the digestive tract, given that this is the first part of the body they encounter. Numerous researchers had explored this possibility, mounting studies that compared outcomes between people taking vitamin supplements and those taking placebos. Now Bjelakovic and colleagues decided to pool these studies in a “meta-analysis,” a “study of studies.” This is recognized to be an effective way to draw conclusions from trials that, by themselves, provide ambivalent results.
They started by scouring the medical literature and various databases for any study that had investigated the link between gastrointestinal cancers and antioxidant supplements. There were loads of these, but only fourteen trials fulfilled the scientific rigor the researchers were after. In all, over 170,000 people were involved in these trials, all of which were appropriately randomized and included placebo controls. Oral antioxidants were used in all cases, although dosages varied, as did combinations. Beta-carotene ranged from 15 to 50 milligrams, vitamin A from 1.5 to 15 milligrams, vitamin C from 120 to 2,000 milligrams, vitamin E from 30 to 600 milligrams every day, or on alternate days for one to twelve years. Selenium supplements (50 to 228 micrograms) were taken every day for two to four years. These doses are not inordinately large, and are in the range of what most people who take dietary supplements consume.
To everyone’s surprise, the supplements offered no protection against esophageal, gastric, colorectal, pancreatic, or liver cancer. The sole positive finding was that, in four of the trials, selenium supplementation showed a significant beneficial effect. But surprise changed to shock when, in seven high-quality trials involving over 130,000 subjects, an increase in mortality was seen among supplement takers! Based on the data they had unearthed, the researchers calculated that for every million people taking combinations of antioxidants, about 9,000 premature deaths were to be expected. Given that millions of North Americans take such supplements, it is little wonder that the Lancet paper received a great deal of publicity, even prompting such sensational headlines as “Vitamins Only Take You Closer to Death.”
That may be overkill. Although there is no question that the Lancet study was well done and has statistical weight, it does leave unanswered questions. For example, what percentage of the subjects had some preexisting condition for which they were taking the supplements? Is it possible that protection against cancer requires that antioxidants be taken for periods longer than twelve years? Maybe these supplements don’t protect against cancer, but what about heart disease or other conditions?
So, what do we do with this study? First of all, we do not shoot the messenger. Supplement promoters have already started to accuse The Lancet of catering to the pharmaceutical industry by publishing a paper that undermines “natural health products.” The argument is that, if people stay healthy by taking vitamins, they will have less use for prescription drugs, so it is therefore in the interest of big pharma to support studies that show supplements to be useless or even dangerous. Bunk. Many pharmaceutical companies make a nice profit from manufacturing supplements.
Unfortunately, there is a growing body of evidence that these supplements are not the saviors they were portrayed to be. A recent meta-analysis of vitamin E studies in the Journal of General Internal Medicine concluded that the vitamin is not useful in the prevention or treatment of heart disease. (For more on vitamin E, see “Vitamin E Doesn’t Deliver Either,” below.) Folic acid and other B vitamins lower blood levels of homocysteine, which has been implicated in heart disease. But a recent double-blind trial showed that patients whose arteries had been opened up by placement of a coronary stent actually did worse if they were given folic acid supplements. And in formula-fed children, vitamin supplementation in the first three months of life was found to be associated with an increased risk of subsequent food allergies.
What are we to make of all this? Jumping to the conclusion that vitamin supplements are dangerous is not justified. Many people in North America have diets that do not provide the recommended daily intake of vitamins, and for them, a onea-day multivitamin is a good idea. But accumulating evidence suggests that it is better to get our nutrients from food than from supplements. There seems to be an almost magical blend of antioxidants, minerals, and as-yet-unrecognized beneficial compounds in fruits, vegetables, and whole grains, a blend that is not replicated in supplements. Maybe we would be better off by taking the money spent on supplements and putting it toward fresh produce. At least until the next study comes out “proving” that some dietary supplement is the only antidote to death. Like I said at the beginning, science can drive you to despair. But then again, there’s this study about how vitamin B6 can increase serotonin levels in the brain and calm you down. . . .