Multivitamins and Cancer Risk: Reading Between the Lines
October 21, 2012 by Robert Wascher
Filed under A Cancer Prevention Guide for the Human Race, Big Pharma, Cancer, Cancer Incidence, Cancer Prevention, Colorectal Cancer, Colorectal Cancer Risk, Drug Company Advertising, Minerals, Multivitamins, Nutrition, Prostate Cancer Risk, Risk of Death, Supplements, Vitamin D, Vitamins, Weekly Health Update, cancer risk, colon cancer, death, health, lifestyle, mortality, prostate cancer, rectal cancer, risk
A new study in the Journal of the American Medical Association claims that a daily multivitamin supplement reduces cancer risk….
MULTIVITAMINS AND CANCER RISK: READING BETWEEN THE LINES
As I discuss in my book, A Cancer Prevention Guide for the Human Race, recent high-level studies of common vitamins, including antioxidant vitamins, has dimmed the prior enthusiasm that these micronutrients can reduce the risk of cancer, or cardiovascular disease, in otherwise healthy individuals who eat a balanced diet. Moreover, recent prospective, randomized, placebo-controlled clinical studies have actually suggested that taking supplements of Vitamin E and Vitamin A (including beta-carotene) may actually be harmful to our health, while recent similar studies of Vitamin C supplements have shown neither apparent benefit nor harm.
Despite the almost uniformly discouraging recent research findings regarding most nutritional supplements and their alleged ability to decrease our risk of cancer and other serious illnesses, many people (as well as nutritional supplement manufacturers…) continue to hold out hope that popping a daily vitamin pill, or other nutritional supplement, will protect them from cancer and other dreaded diseases. (Meanwhile, most people still tend to ignore the evidence-based cancer prevention lifestyle and diet practices that I describe in A Cancer Prevention Guide for the Human Race, and which have been linked, by hundreds of reputable clinical research studies, with a 40 to 60 percent reduction in cancer risk.) So, it is not surprising to see the extensive and favorable media coverage that is being given to a newly published clinical study looking at the potential impact of daily multivitamin supplements and cancer risk, and which appears in the current issue of the Journal of the American Medical Association.
The Physicians’ Health Study II is a large, ongoing, prospective, randomized, placebo-controlled study of 14,641 male physicians in the United States. All of these men were at least 50 years of age when they entered into this public health study (the average age of all study participants when they entered into this study was 64 years of age). This study has observed health outcomes in this very large group of male physicians for an average of 11 years now, and the study’s authors have now reported on the impact of taking a daily commercial multivitamin supplement upon cancer risk and cancer-associated death rates.
To summarize the findings of this very large public health study, the male physicians in this study were secretly randomized to receive either Centrum Silver (a commercial multivitamin and mineral supplement) or a placebo (sugar) pill. At the time of their entry into this study, 1,312 of these male volunteers were noted to have a prior personal history of cancer. Following more than 11 years of observation, 2,669 of these physician volunteers were subsequently confirmed to have developed cancer, including 1,373 cases of prostate cancer and 210 cases of colorectal cancer. When compared with the men who were randomly (and secretly) assigned to the placebo group, the men who were assigned to the multivitamin supplement group experienced an observed, and modest (8 percent), but still significant, reduction in the risk of being diagnosed with cancer.
While this 8 percent reduction in overall cancer risk has been widely trumpeted by other media sites, it is important to note several significant caveats before you run out to the drugstore and buy a case of Centrum Silver. When one looks at the statistical analysis of the data that resulted in the claimed 8 percent reduction in cancer risk, one immediately notices that the so-called “confidence interval” for this claim extends to 0.998, which is right up against the limit of 1.0 that would render these findings statistically insignificant. Therefore, the single, sole positive finding in this study of a modest decrease in overall cancer incidence is, itself, at the very borderline of what most statisticians would consider to be a statistically significant finding.
In addition to the single modest (and only barely statistically significant) positive finding of this study, as I have noted above, there was no significant correlation between multivitamin use and the risk of developing prostate cancer, colorectal cancer, or, indeed, any other individual type of cancer. The absence of any identifiable decrease in the risk of any individual type of cancer in this study, likewise, further calls into question the validity of this study’s single, and statistically borderline, positive finding of an 8 percent reduction in overall cancer incidence among the group of men who were randomized to receive a daily multivitamin tablet. Moreover, this study also failed to reveal any detectable reduction in the cancer-associated death rate among the men who received a daily multivitamin tablet.
The rather breathlessly favorable media reaction to this study’s conclusions vividly illustrates how the superficial reporting of seemingly favorable clinical research findings can mislead the public into accepting overblown or invalid conclusions, such as those made by the authors of this particular research study. As I discuss in A Cancer Prevention Guide for the Human Race, most of the published research in the area of cancer prevention research is of relatively low quality in terms of the methods used to conduct such research. Moreover, as this particular prospective, randomized, placebo-controlled study shows, even clinical studies that actually utilize higher level methodologies still require both a careful and critical analysis of their findings and claims, and the conclusions of such studies should not be simply accepted at face value. While this multivitamin study makes the very simple and straightforward claim that taking a commercial multivitamin and mineral supplement “significantly” reduces the incidence of cancer (at least among middle-aged and elderly male physicians), even a cursory evaluation of this study’s data and conclusions confirms that there is likely to be little or no overall health benefit, in terms of cancer risk and cancer-related death reduction, associated with taking a daily multivitamin and mineral supplement in otherwise healthy and well-nourished adults. As the old saying goes, if something seems too good to true, it probably isn’t…..
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Disclaimer: As always, my advice to readers is to seek the advice of your physician before making any significant changes in medications, diet, or level of physical activity
Dr. Wascher is an oncologic surgeon, professor of surgery, cancer researcher, oncology consultant, and a widely published author
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