A recently published Cochrane Review of a Danish meta-analysis has
prompted news headlines around the world in the direction of "Vitamins
may reduce lifespan" and "Certain vitamins could increase mortality".
But the meta-analysis is ill suited to draw broad conclusions about the
health effects of dietary vitamin and antioxidant supplements taken in
The meta-analysis has been criticised by medical experts for only
including a small percentage of available studies, and it has been
pointed out that a few studies upset the results of the entire report.
Specificly, two large, well known, high-dosage beta-carotene trials
involving smokers provided more than half the deaths in the analysis. An
reanalysis of the data, where all 25 trials on beta-carotene were
excluded, no longer showed any significantly increased mortality due to
either vitamin A or E.
Several of the studies are conducted with people who were chronically
ill and who were given extremely large doses of certain nutrients in
order to see if that would cure them. Such studies are not compatible
for comparison with studies carried out on healthy individuals who have
been taking vitamin and mineral supplements containing nutrient doses
comparable to those found in food supplements.
Also, several of the studies involve such large doses of vitamin E and
vitamin A that the levels would never be approved for dietary
supplements or high-strength vitamin- and mineral preparations. In fact,
some of the doses were potentially toxic, yet the media uncritically
link the results of the research to food supplements.