The initial observational studies had suggested that intake or blood levels of vitamins E and C were associated with reduced risk of certain cancers. Further, several possibly mechanisms were also put forth by which antioxidant micronutrients such as vitamin E and vitamin C may delay various steps in carcinogenesis (the process by which normal cells are transformed into cancer cells.)

However, there didn't exist a definitive proof that vitamins E and C can reduce the risk of overall or site-specific cancers. Consequently, the National Institutes of Health invested hundreds of millions of dollars in clinical trials involving more than 50,000 participants, to seek large-scale randomized trial evidence for the supplements' efficacy in preventing cancers.

The verdict of the trials is pretty much out and the conclusion reached is that vitamin C, vitamin E and selenium supplements don't reduce the risk of prostrate cancer and other cancers.

As a result, use of these supplements for the prevention of cancer in middle-aged and older men may not be effective. The results have been published in the December 9 edition of the Journal of the American Medical Association (JAMA)

The Contrapuntal

As soon as the results were made known, several experts from the medical industry called to question the weaknesses inherent in the studies that may somewhat undercut their conclusions attacking the vitamin supplement's effectiveness.

Drug trials and dietary supplement trials are different. Pharmaceutical drugs typically are artificial substances not naturally present in our bodies, whereas vitamins are naturally present in our bodies. So when subjects consume pharma drugs, it's known what quantity of a substance is present in their system, but it's a different case with vitamins. As a result, a baseline exposure that needs to be taken into account to measure an improvement may be missing from the vitamin studies.

Some experts also suggest that we may still not know whether the results would be different, if, for instance the dosages had been higher, or if the subjects were studied for another ten years or so, etc.

Also, that the observed differences between the new studies and previous supportive studies may be because the effects of nutrients in the human body are complex and are affected by many variables.

It seems that there's room for the claims of both the studies conducted and the skepticism surrounding the “sweeping” claims made by the study results.

Further, it's not just cancer they supposedly help alleviate, rather dietary supplements save billions in health care costs possibly helping with some of the top issues during the 2009 financial crisis.

On the whole it appears that there may be evidence against their efficacy against cancers, however, more work may still need to be carried out to reach a truly “definitive” conclusion.