Excessive Vitamin Supplements Can Cause Cancer, Study Shows

My dad, who was a clinical nutritionist, had a mantra that ruled his life. And to the best of his ability, he made sure it ruled his kids’, too:

You get out of life what you put into it.

It ruled his work as a researcher, as well. He was known to grumble about short-term controlled experiments that claimed that a particular substance or chemical if consumed, would cause cancer.

“Anything taken in excess can cause problems,” he told me once. At the time, he was referring to clinical studies that suggested cyclamates, an artificial sweetener, would cause cancer. It was yanked from sugar-free foods in the United States as a result of a 2study that reported that mice fed cyclamates in very large amounts contracted cancer. It wasn't that he objected to the substance being regulated, but the way the research was done.

So I find myself wondering what my dad would think if he were here today and had read the new research on vitamins B6 and B12.

For years, getting enough B12 was considered a challenge for vegetarians and vegans, who often unknowingly were at risk for vitamin deficiencies. Invariably, my discussions with my dad about my own dietary preferences seemed to lead to this point: The very best sources of the elusive vitamin B12, my dad would insist, was red meat. The dedicated and well-educated vegetarian, he would gently nudge, could get enough B12 from vegetable, egg and milk sources, but it was difficult. "Fortunately," he would always remind me, "you need very, very little B12 in your diet." The average adult needs 2.4 mcg of vitamin B12 and between 1.3 and 1.7 mg. of Vitamin B6.

Today, however, accessing enough of those two vitamins clearly isn't such a problem. Thanks to modern food engineering, we have a panoply of vitamin and mineral supplements that can meet the needs of just about every dietary habit and health challenge. Ironically, it can also meet just about any medical premise that comes up -- Including the idea that taking more than the RDA (required daily amount) of Vitamin B6 and Vitamin B12 are actually not only OK, but good for the average person. That may be in part because until recently, hard-core quantitative data about the health risks of taking too much vitamins B6 and B12 has been hard to come buy.

But a new study published in September suggested that there is a backside to our new technological know-how: Toxic consumption. Vitamin and mineral supplements are some of the few "consumables" that the Food and Drug Administration doesn't regulate. It doesn't regulate availability and it doesn't set limits on dosages or a company's ability to state that a given amount will actually benefit the consumer. When it comes to some supplements, like your garden-variety fruit-flavored vitamin C, that's not generally a problem (unless, as the Mayo Clinic points out, you're into consuming mega doses of the vitamin, which can cause intestinal upset and other problems). There's been a load of research that (so far) has shown that the body discharges excessive amounts of vitamin C. It's been shown to help boost immunity, but excessive amounts aren't retained in the body. But that's not the case for B6 and B12, scientists tell us. According to research published jointly by investigators at the Ohio State University College of Medicine (Columbus, OH), Fred Hutchinson Cancer Research Center (Seattle, Wash.) and College of Public Health and College of Medicine, National Taiwan University, (Taipei, Taiwan), taking excessive amounts of these two vitamins raises the risk of lung cancer significantly in men. What is impressive about this particular research, and what makes its findings compelling is the way it was done. In 2000, researchers began following a broad cross-section of 77,000 individuals (ages 50-70) in the state of Washington to determine the effect of excessive intake of certain vitamins. Theodore M. Brasky and his team (Emily White and Chi-Ling Chen) already had reason to suspect that there was a possible link between intake and lung cancer from a previous small study. But they wanted a long-term, definitive view of just what kind of risk a high-intake of these two elusive nutrients really posed. What they have found so far, is that although women don't appear to be at increased risk for lung cancer when taking high amounts of either vitamin, men's chances of developing the disease more than doubles with very large dosages. And men who smoke face a 3 to 4-fold risk of cancer. The research is still ongoing, but one of the takeaways from these findings is the health implications of having no federal regulation. The 1994 Dietary Supplement Health and Education Act pretty much defers supplement regulation to the industry. The FDA has been known to put out warnings and restrict access when there's been a safety problem with a specific product, but it permits self-regulation. And as the researchers point out, the average consumer has access to dosages that are often dozens to thousands of times higher than the FDA's recommended limit for that vitamin or mineral. In other words, a company can promote 6 daily dosages of 1 mg of B12 by spray, or a fruit-flavored supplement that gives you more than 16,000 times the RDA of that vitamin based on its own research. As far as selling it to the consumer, the company only needs to back up its assertions with research that defends its claim. And this is where my dad's motto seems so worthwhile about getting exactly what you put into it. The researchers followed participants for more than a decade -- a significant investment when it comes to career and time -- building a case not from marketability but hard-core (and hard-to-come-by) results, the kind of thing that consumers often expect from the FDA's own assessments and regulation. What hasn't been discussed a great deal, either in the synopsis of Brasky and his team's findings or in the media's coverage of this, is that deficiencies of these two vitamins are also linked to health problems, and in some limited situations, cancer. Patients with Celiac disease are often deficient in these two vitamins and pose a higher risk for cancer from inability to absorb nutrients correctly. Vitamin deficiencies can be a real challenge for individuals who have health or diet concerns. So access to vitamin supplements doesn't just amount to an arbitrary decision of lifestyle. Still, this study proves better than most that both the manufacturing industry and the FDA have a role to play when it comes to ensuring that consumers get what they expect from supplements: better health. Flickr images: Neeta Lind; Colin Dunn