Update: Deadly Multivitamins - Supplement Hit Job #42
Last month, I wrote a post questioning the conclusions of a poorly designed National Cancer Institute study that suggested taking “excessive” multivitamins could increase your risk for prostate cancer.
More recently, the Life Extension Foundation (LEF) put together an even more damning and detailed critique of the study’s results that raises other excellent points worth considering:
1. Study participants may have been mis-classified.
As mentioned in my earlier post, the study used self-reported food frequency questionnaires (FFQs) to ask study participants about prior supplement usage. FFQs are subject to significant error, as participants may over- or under-report supplement use.
As LEF notes:
Questionnaire-based information collection is limited in accuracy to the memory recall of the study subjects. The majority of people cannot recall what they ate for breakfast one week ago, or which shirt they wore to work two weeks ago, or how many gallons of gas they purchased during their last trip to the gas station, never mind specific doses and frequency of use of a myriad of dietary supplements months or years ago.
But it gets better when we learn what the researchers actually did in this case:
In this government-funded study bashing multivitamins, the researchers had the audacity to place each subject who stated they did not know how much vitamin E they took into the 400 IU a day category. This means when the results where tabulated to see if multivitamin use was associated with prostate cancer risk, men who may or may not have taken any vitamin E were deemed to have taken 400 IU a day.
Men who reported taking even one multivitamin supplement a month were recorded as taking a multivitamin every single day. This meant that when the data was tabulated, those who may have taken as few as twelve multivitamin supplements a year where considered to have taken a multivitamin each day.
If one were designing a study to make it impossible to conclude anything meaningful from the results, this would be a good way to do it.
2. Several other rigorous studies with well-defined design criteria have shown different nutrients may help to prevent the development of prostate cancer.
LEF highlights the selenium study that I mentioned in my earlier post, as well as several other studies that note the potential protective effects of other antioxidants, including the gamma-tocopherol form of vitamin E.
The latter nutrient may be especially important. There are 8 naturally-occurring forms of vitamin E, including 4 tocopherols and 4 tocotrienols. LEF has long reported on the importance of not supplementing with just a single form of vitamin E (like the common alpha-tocopherol form), but instead using a broad-based form of vitamin E high in gamma-tocopherol, which is the form found in highest quantity in food.
LEF cites another recent National Cancer Institute study that noted the potential importance of this form of vitamin E:
For gamma-tocopherol, men in the highest fifth of the distribution had a powerful five-fold reduction in the risk of developing prostate cancer than men in the lowest fifth of the distribution. Statistically significant protective associations for high levels of selenium and alpha-tocopherol were observed only when gamma-tocopherol concentrations were high. The men participating in the study claiming that multivitamins increased aggressive prostate cancer risk were not obtaining any gamma tocopherol in supplement form.
3. Detection (diagnosis) bias may have been present.
In this study, a family history of prostate cancer was associated with supplement use, and prostate cancer PSA screening was most frequent among heavy users of multivitamins, consistent with other survey data showing that men who used supplements were more likely to have PSA examinations than nonusers. Therefore, there is increased prostate cancer detection among this subpopulation of men who are heavy supplement users and who are more likely to seek health care tests owing to a positive family history of prostate cancer. This is a form of detection or diagnosis bias.
In short, people with a family history of prostate cancer or who frequently screen for prostate cancer are more likely to identify prostate cancer. Those groups are also greater users of supplements, but that doesn’t mean the supplements caused the cancer.
In fact, when excluding men diagnosed with prostate cancer within the initial two years of the study period, the relative risk of advanced prostate cancer with heavy multivitamin use no longer existed.
The study authors actually mentioned this possibility of detection bias, but it wasn’t reported by the media.
Bottom Line
LEF notes that this study is yet another in a long list of flawed studies that depict nutritional supplementation as contributing to, rather than helping to prevent, disease.
The organization even suggests an active conspiracy between the government and the pharmaceutical industry to discredit nutritional supplements. There’s not explicit evidence of that, but the recent barrage of negative reports (and the paucity of media coverage of positive reports, such as the amazing vitamin D / cancer study results just released) certainly raises questions.
As does this:
Cancer industry profits require lots of cancer victims
The “cancer industry” is gigantic. Like any other business, profits are dependent on consistent and predictable volume. The American Cancer Society predicts that 1,444,920 people will be diagnosed with cancer in the United States in year 2007.
Those involved in the “cancer industry” have a huge financial stake in 1,444,920 Americans contracting cancer this year. A substantial body of research, however, indicates that these cancer rates could be sharply reduced.
For example, very strong evidence indicates that higher-potency vitamin D supplements could cut the rate in which people contract cancer by 50% or more. Yet the federal government makes it illegal for those who sell vitamin D supplements to make a cancer claim on the label of their product, thereby denying this knowledge to the majority of Americans.
If cancer incidences did decline by 50%, an enormous economic upheaval would occur throughout the “cancer industry”. There is thus a huge economic bias in keeping Americans in the dark about what they can do to reduce their risk of contracting cancer.
Something to think about …
Related Posts
Deadly Multivitamins - Supplement Hit Job #42
Killer Antioxidants - Supplement Hit Job #37
Questioning the Usefulness of Nutritional Supplementation
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