Oct 6, 2004 – Vitamin Supplements May Not Help Prevent Gastrointestinal Cancer, Meta-Analysis1 of 14 clinical trials. Certain combinations of supplements could even increase the risk of premature death, as published The Lancet in a recent edition.
According to this meta-analysis from Denmark, people taking a combination of supplements with antioxidant properties such as beta-carotene, vitamin A, C, and E, were at greater risk of premature death than those given a placebo.
In addition, these supplements – taken alone or in combination – had no preventive effect against cancers of the stomach, esophagus, colon, liver and pancreas. On the other hand, selenium seemed to show some benefit, although the study authors judged the clinical trial methods for this supplement to be inadequate or of poor quality.
These results have revived the debate about vitamins as a preventive treatment against certain cancers. Several observational studies tend to show that a diet rich in antioxidants (spinach, carrots, blueberries, etc.) is associated with a decrease in the frequency of cancer. The Danish analysis looked at the consumption of antioxidants in tablets and concluded, like previous clinical studies, that their preventive benefits could not be proven.
The Briton David Forman, an expert in epidemiology, says that we should not conclude that these vitamins are dangerous for health. Although clinical trials included 170,525 cases, the assessment of the risk of premature death came mainly, he said, from cases where individuals already had several factors that placed them at high risk of developing cancer. Mr Forman said the results of the Danish study should be considered preliminary.
Antioxidants have grown in popularity since it was discovered that they may help prevent cardiovascular disease and some cancers. The Canadian Cancer Society prefers not to comment on this use of vitamins in order to reduce the risk of cancer. She prefers to reiterate her main recommendations: eat healthy, avoid smoking and keep in good physical shape.
Marie france Coutu – PasseportSanté.net
According to National Post and Lancet
1. Bjelakovic G, et al, Antioxidant supplements for prevention of gastrointestinal cancers: a systematic review and meta-analysis., Lancet, 2004, Vol. 364, 1219-28