Two recently published studies that pointed to adverse results with the consumption of dietary supplements have raised questions and concern among industry leaders. While one study indicates an association between dietary supplement intake and increased mortality risk, the other suggests that supplementation with vitamin E significantly increased the risk of prostate cancer among healthy men. Many experts believe otherwise. Here are some insights that bring the shortcomings of these studies into the limelight.
Dietary Supplements and Mortality in Older Women
This study (printed in Archives of Internal Medicine) evaluated the usage of vitamin and mineral supplements among 38,772 women in the Iowa Women’s Health Study, with a mean age of 61.6 years. The participants self-reported their supplement use in 1986, 1997 and 2004. A total of 15,594 (40.2%) deaths were identified through the State Health Registry of Iowa and the National Death Index through December 31, 2008. Multivitamins, vitamin B6, folic acid, iron, magnesium, zinc and copper use were found to be associated with increased risk of total mortality when compared with corresponding non-use, but use of calcium was inversely related. The study concluded that several commonly used dietary supplements may be associated with increased mortality risk, the association being the strongest in iron.
Conversely, Huffington Post writer and practicing physician Mark Hyman, MD, founder of The UltraWellness Center, asserts that all doctors and scientists understand that this kind of study does not prove cause and effect. Upon carefully reading this study, he observed many flaws that question its validity. He observed that even though 13.5% of vitamin users and 7.2% of non-vitamin users took hormones, hormone replacement was not taken into consideration in the study. According to previous research, it was found that hormone therapy dramatically increases the risk of heart attack, stroke, breast cancer and death. He proposes that while the vitamins may have been protective, their benefits could have been overshadowed due to the harmful effects of hormones in the vitamin users.
Hyman also notes that the patient background was ignored and the reason why the patients initially started taking supplements was unknown. “People with certain health conditions who consumed supplements could potentially face increased chances of mortality due to their pre-existing conditions like cancer or a heart attack,” he says. He also believes that the study did not present a realistic comparison between vitamins and other medications. More than 100,000 people die annually even due to properly prescribed medications in hospitals; this fact was not addressed by the researchers and is a huge limitation of the study. Hyman also adds that there were no accounts of the quality or forms or dosages of the vitamins used and the intake of vitamins that have biologically inactive or potentially toxic forms of nutrients could limit their benefits.
According to the Alliance for Natural Health (ANH), the data were self-reported by the subjects only three times over a period of 19 years. They believe that the data are unreliable and do not constitute a valid scientific study. The associated risks were barely statistically significant and were not bolstered by a medical investigation or a biological plausibility study. No analysis was conducted based on which combinations of vitamins and minerals were actually consumed, and no causative analysis was done beyond grouping for “cancer,” “cardiovascular disease,” or “other.” ANH states that the interactions of potential compounding risk factors are always tremendously complex and were ignored in this study.
Adding to these concerns, Robert G. Smith, a research associate professor at the University of Pennsylvania, observed that the study did not take into account the effect of doctor’s recommendations of daily multivitamins for their sicker patients. More details about his views can be found in this month’s Vitamin Connection column on page 34.
Jack Challem, The Nutrition Reporter, highlights one positive finding, noting, “The study’s only really significant association was between iron supplements and a greater risk of death, which has been known for years.” He feels that older women (or men) have a greater likelihood of disease and death because of their age, and their consumption of multiple drugs can be a common cause of illness and death.
The Natural Products Association (NPA) advocates that consumers use dietary supplements as a part of a healthy lifestyle. Cara Welch, Ph.D., NPA’s vice president of scientific and regulatory affairs, says, “I’m always pleased to see analysis on the long-term effects of supplementation. This study, however, is quite limited in scope; the data is observational and self-reported, so contributing factors are not addressed.” Welch also notes that plenty of studies demonstrate the merits of dietary supplements and the general public should not be advised against taking supplements to address their mineral or vitamin deficiencies.
Vitamin E and the Risk of Prostate Cancer
An initial report on the Selenium and Vitamin E Cancer Prevention Trial (SELECT), published in the Journal of the American Medical Association, indicated no reduction in risk of prostate cancer with either selenium or vitamin E supplements. But, there was evidence of a statistically insignificant increase in prostate cancer risk with vitamin E. So, this new study aimed to determine the long-term effect of vitamin E and selenium on the risk of prostate cancer in relatively healthy men. The randomized trial recruited a total of 35,533 men (age 50 years or older for black men; 55 years or older for all others) from 427 study sites in the United States, Canada and Puerto Rico between August 22, 2001 and June 24, 2004.
The primary analysis consisted of 34,887 men who were randomly assigned to four treatment groups: selenium (8,752), vitamin E (8,737), both agents (8,702) and placebo (8,696). The final data were collected July 5, 2011. Since the primary report, the trial had 54,464 additional person-years of follow-up and 521 additional cases of prostate cancer. In the placebo group, 529 men developed prostate cancer, compared with 620 in the vitamin E group, 575 in the selenium group and 555 in the selenium plus vitamin E group. In comparison with placebo, the absolute increase in risk of prostate cancer per 1000 person-years was 1.6 for vitamin E, 0.8 for selenium and 0.4 for the combination. It was concluded that supplementation with vitamin E significantly increased the risk of prostate cancer among healthy men.
Challem states that the vitamin E used in the study was synthetic and very different from the natural form, which could potentially account for the finding. He also notes that the diagnoses of prostate cancer were made years after the men had stopped taking the supplement, which could mean that the cancer came from another cause or a combination of causes. “Cancers are typically so slow-growing that many of them were probably undetectable when the study began,” he concludes.
According to Eric Klein, M.D., the study’s lead author and chairman of the Glickman Urological and Kidney Institute, Cleveland Clinic, there is no biological explanation for why those who took vitamin E are at higher risk of developing prostate cancer and additional research is needed to better understand the current findings. Edward Messing, M.D., chairman of the Department of Urology, University of Rochester’s Medical Center, finds that despite the apparent increased risk of prostate cancer indicated in the study, the number of participants who actually developed the disease was still relatively small. J. Kellogg Parsons, M.D., a urologic oncologist at UC San Diego Moores Cancer Center and one of the SELECT study co-authors, affirms that there is no direct evidence that vitamin E causes prostate cancer and that the reason as to why patients who took 400 IUs of vitamin E in the SELECT study had a greater chance of being diagnosed with prostate cancer is yet to be determined.
Published in WholeFoods Magazine, December 2011