Wednesday, March 14, 2012

Vitamins: A Cautionary Tale

Do you take any vitamins or supplements?  I do, and given the statistics I list next, sounds like I’m not the only one.

According to survey data collected between 2003 and 2006 by the Centers for Disease Control and Prevention (CDC), about 53% of Americans take some sort of supplement.  This is percentage is up from 40% during their previous data collection between 1988 and 1994. 

The marked increase in the percentage of Americans taking supplements can be attributed to several recent supplement fads.  Over the last few years it has become very popular for medical professionals to recommend high doses of vitamin D and E.  Dr. Michael Holick of Boston University is one such advocate for high doses of vitamin D.  “There’s overwhelming evidence…that increasing your vitamin D intake can make substantial improvement in your overall health and welfare,” he explains, “and there is no downside to increasing your vitamin D intake.”  Not only does Dr. Holick argue that high levels of vitamin D will lessen one’s likelihood of developing osteoporosis (which is agreed upon in the scientific community), but he posits that vitamin D may decrease instances of cancer, heart attack, arthritis, Alzheimer’s, diabetes (both types), autism, and even the flu. 

Sounds like a pretty necessary vitamin based on Dr. Holick’s evidence, but it is endorsements like these that lead to the dramatic increase in vitamin intake noted by the CDC. 

Contrary to Dr. Holick’s opinion, there are those who doubt the “overwhelming evidence” of the importance of vitamin D.  Dr. JoAnn Manson, chief of preventive medicine at Harvard-affiliated Brigham and Women’s Hospital points out that nearly all of the studies involving vitamin D are “observational” studies.  Rather than the ideal “experimental” design involving randomized trail groups, “observational” studies simply find people with low and high levels of vitamin D and correlate those levels with the participants’ overall health.  The problem with these studies is that there are many other potential variables not accounted for.  For example, those with high levels of vitamin D could be healthier because they get in the sun and exercise more, and those with low levels of vitamin D could be unhealthy because of bad eating habits…not just because of vitamin D levels.  “We don’t yet have the large-scale, randomized clinical trials showing benefits in terms of prevention of cardiovascular disease, cancer, diabetes, hypertension, cognitive decline, depression, autoimmune disease,” Manson explains.  To further her claim, there are “observational” studies on vitamin D that suggest that large doses may not actually help you.

The Institute of Medicine’s Food and Nutrition Board, which makes official recommendations on dietary intake, says that advocates of high doses of vitamin D are overstating the effectiveness of the vitamin.  Dr. Manson, who is also one of the 14 panel members at the Institute of Medicine, explains their decision to only slightly increase the recommended daily dose of vitamin D compared to the huge increases some are advocating: “The evidence was inconsistent and inconclusive as to a benefit of vitamin D in preventing cancer, cardiovascular disease, diabetes, autoimmune disorders and many other health outcomes beyond bone health.” 

A similar story can be told for another recently popular vitamin: vitamin E.  Past studies have suggested that high doses of vitamin E could help prevent prostate cancer.  However, a new study testing this conclusion found that vitamin E may actually increase the risk of prostate cancer.  What’s more, this new study is the largest such study to test the relationship between vitamin E and prostate cancer using randomized clinical trials.

The fact is that we do not yet have definitive information on the benefits and risks of taking large doses of various vitamins.  In the upcoming years it will be important to keep up with new research on this subject, rather than prescribing to a fad.  It would also be a good idea to take a deeper look at your vitamin jars at home.  The multivitamins we take often have much higher percentages of various vitamins than the daily recommended dose, and if your multivitamin contains a high dose of vitamin E, men should consider changing multivitamins.

Often times we turn to supplements for a quick fix.  We hope that they will prevent disease, make us healthier, and maybe even make up for some of our less than healthy habits.  Unfortunately, we are still uncertain whether large doses of some vitamins will help us, hurt us, or make no difference at all.  Until we have more information, I would suggest slowly adopting healthier eating habits that will supply you with all of the nutrients you need. 

~ Jessica


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