The loyal followers of my blog may recall that two weeks ago I discussed the subject of diet and cancer, citing the work of T. Colin Campbell, Ph.D. and his book The China Study. To summarize, Dr. Campbell argued, persuasively I thought, for a vegetarian diet, specifically avoiding animal protein Not mentioned in that discussion was the dismissive approach Dr. Campbell took to the use of extra vitamins to improve health. In the last month perhaps the final shoe has dropped on that discussion. In an important public health journal, The American Journal of Epidemiology, Dr. Park et al present their recent analysis of the Multicohort Ethnic Study, conducted between 1993 and 1996. With at least eleven years of follow up from the close of the study, they collected over 182,000 health records to analyze. They looked at vitamin use, assessed by questionnaire, and found no association between use of multivitamins and the subsequent development of cancer. The power of the study was in the number of enrollees and the complete absence of a difference in the frequency of cancer based on the number of vitamin pills ingested per week.
Previous studies had suggested a potential benefit. In the mid 1990’s there was a small landmark study published suggesting that the use of selenium (a trace metal) supplementation dramatically reduced the incidence of prostate cancer. A much large study recently completed debunked this observation. Two moderate sized studies suggested that folic acid might reduce the risk of colorectal cancer. However, the current study joins the results from two very large and well done trials, the Women’s Health Study and the NIH-AARP Diet and Health Study, which showed no protective effect of extra vitamins. The Cancer Prevention Study II and NIH-AARP actually suggested a slight increased risk of prostate cancer with vitamins.
In the 1980’s another landmark study, this time from China, suggested that smokers who took a vitamin pill daily had a lower risk of lung cancer. When that study was replicated in the United States and Scandinavia there was an unexpected increased incidence of lung cancer among people who took β-carotene (a form of Vitamin A) and Vitamin E. No explanation for this observation has ever come forth.
So, where does this leave us? Dr. Campbell suggests that the wisdom of fruits and vegetables is in their ratio of various vitamins which we cannot hope to duplicate with pills. So let’s go back to the recommendation of Michael Pollen: “Eat food. Not too much. Mostly plants.”