Flawed studies lead to flawed opinions on the benefits of multivitamins

Unbalanced information for buyers of multivitamins.

It’s rare these days to pick up a paper without reading an alarming article about how what you’re eating, drinking, and breathing is harming your body. But what’s even more alarming, is that the studies these reports are based on are often critically flawed. Eggs, butter, and even milk have all been unfairly maligned by misinterpreted results and misled journalism, only to be redeemed years later.

Now, following the publication of a review by the United States Preventive Services Task Force (USPSTF), multivitamins have fallen into the line of fire. The USPSTF’s findings, that vitamin and mineral supplements have no preventative benefit for cardiovascular disease or cancer, have been widely taken up with the media and led to a slew of articles arguing against nutritional aids.

While doubtless worrying many — more than half of Americans take a multivitamin of some sort — these broad pronouncements are rarely what they seem, and indeed, that is the case here.

A track record for misleading advice

Until recently the USPSTF was a relatively low-profile organisation, only occasionally lifting its head above the ramparts. They first courted major controversy in 2009 by recommending that men 75 or older do not undergo Prostate Specific Antigen (PSA) tests to detect prostate cancer, later revising that recommendation to include men of all age groups. At the time, the USPSTF argued that the PSA test was relatively ineffective and possibly harmful. Were they right?

Perhaps not. Dr. Timothy E. Schultheiss, professor and director of radiation physics at City of Hope in Duarte, California, and author of a new study on prostate cancer prevalence in America, argues that under the USPSTF’s recommendations, prostate cancer rates have actually grown. Schultheiss’s research found a notable increase in higher-risk cases between 2011 and 2013, a trend that could produce an additional 1400 prostate cancer deaths annually.

The USPSTF has also been attacked for its stance on mammograms as a preventative measure for breast cancer. Their new guidelines, that women aged 50 to 74 have a mammogram every two years, and women aged 40 to 49 should make their own decision in consultation with doctors, have drawn widespread ire from various individuals and groups, including breast cancer survivor and U.S. Rep Debbie Wasserman Schultz.

The frustration with the USPSTF stems in part from its lack of transparency. In response to PSA recommendations, Drs. Deepak A. Kapoor, MD and Davod M. Albala, MD wrote in the Medical Society of the State of New York’s News of New York:

We cannot even ask how the USPSTF managed to be so wrong. The USPSTF is exempted from both the Federal Advisory Committee and Administrative Procedures Acts; consequently, it is not required to hold meetings in public; consider public comments; or disclose its methodology. There is no recourse for those harmed by its decisions and these powers are expanded under the Affordable Care Act. The decision on prostate cancer screening, which overrules experts in the field and cherry-picks data to arrive at a pre-determined outcome, illustrates how dangerous such unaccountable power can be.

Perhaps unsurprisingly, there are a number of equally worrying problems with the USPSTF’s pronouncement on multivitamins.

Is there methodology to the madness?

One of the major problems with the USPSTF’s review was their definition of multivitamins themselves. By including studies which involved only three nutrients in their analysis, the organisation belies the physiological complexity of cardiovascular disease and cancer. Both of these conditions are tremendously multifaceted in their causes, and involve irregularities in a wide range of bodily processes and functions. Indeed, the whole premise that multivitamin supplementation is founded on — that proper nutrition is rarely a case of magic-bullet cures — tells us that intake of only a few compounds will not produce the same robust health benefits as a more holistic regime.

Another issue is that the USPSTF’s analysis itself is inherently biased against establishing benefits for multivitamin supplementation. By design, their tests are meant to assess pharmacological drugs with explicit actions and areas of activity, not nutritional compounds formulated to support a whole range of bodily mechanisms. Equally, it is significantly harder to account for the already present, and significantly varying, intake of various nutrients in participant groups, an non-issue with synthetic drugs that could not be found naturally in individuals.

This flawed methodology also bled over into the USPSTF’s data selection. Of the 154 clinical trials in which the words “multivitamin” or “multivitamins” appear on PubMed alone, only two were considered appropriate for inclusion; their analysis of 16 nutrients encompassed the results of only 26 studies; and of all the studies analysed, only one included women. The USPSTF itself admitted they included “no data on a ‘true’ multivitamin in women”. Similarly, the USPSTF was quick to exclude a whole range of data it deemed statistically insignificant, particularly those that showed benefits for supplementation.

Critics have also pointed out the relatively short duration of the trials included in the review, with only two of moderate duration (11.2 and 7.5 years). Sadly, it was precisely these two studies which actually presented a reduction in cancer risk among men taking multivitamins. Both cancer and cardiovascular disease are conditions that take years to develop and eventually manifest, and are influenced by a lifetime of nutrition and lifestyle. Expecting short-term results from limited supplementation flies completely against nutritional science which recommends a comprehensive and continuous intake of essential compounds.
While the USPSTF seems to have set standards for its review that intentionally exclude evidence of the benefits of multivitamin supplementation, they were remarkably less rigorous about studies that supported its apparently foregone conclusion. The Selenium and Vitamin E Cancer Prevention Trial (SELECT) apparently proved that neither compound had protective impacts for prostate cancer, despite the fact that the specific vitamin E compound used, all-racemic alpha-tocopherol acetate, is widely considered one of the least effective formulations of this essential nutrient.

So should I take a multivitamin?

While these questionable studies are all too common, it’s important to remember that you should always consider the full facts, your own health, and do your own research. Everyone is different, with their own unique physiology, diet, and lifestyle, and wide-ranging pronouncements based on incomplete data should always be taken with a grain of salt.

Folic acid, only recently blamed in the media for potentially promoting colorectal tumours, is now once again being championed by a study from the Harvard School of Public health. While the participants, as a whole, did not seem to benefit from folic acid supplementation, those participants who had started with the lowest folic acid intake actually experienced a distinct reduced risk of tumour recurrence. The importance of this finding cannot be understated.

Multivitamin support may not be for everyone: if you have a wide and varying diet that includes plenty of fresh fruit and vegetables, you may be nutritionally complete; but if you are one of the many whose lifestyles could do with some balance, multivitamins offer a potent opportunity to top up on essentials.

Sadly, and ironically, it is generally the healthiest of us who take multivitamins, and scare-tactic news headlines, spurred on by flawed and misleading research, only serve to frighten away those who have the most to gain.