Posted by: [log in to unmask] (John Mercer)

Key et al., BMJ 313:775 (1996) found that the breast cancer mortality
ratio of vegetarians was significantly greater (1.65) than that for
health-conscious nonvegetarians. While this higher mortality might be
attributable to a higher proportion of vegetarian women that have never
had children, there certainly is no evidence that vegetarianism helped
at all.

The overall mortality ratio was slightly higher for vegetarians (1.07)
than for nonvegetarians in this group of uniformly health-conscious
people, but not significantly so. The mortality ratio for the group as a
whole was half that of the general population, showing the beneficial
effects of their lifestyle.

The only dietary practice found to result in a significant reduction in
mortality from specific diseases was eating fresh fruit daily.

In case you were going to invoke the genetic fallacy as a rebuttal, two
of the authors note that they are members of the Vegetarian Society UK.