Ruediger Hoeflechner humorous example is apropriate--a lot of popular books
and articles on diet are based on similarly silly logic and total lack of
any real research.  While popular publications shouldn't be expected to be
as rigorous and exquisitely detailed as peer-reviewed publications, the
majority of writers of such books lack even the most haphazard standards of
support or proof.

Witness the number of vegetarians who continue to insist that the
evolutionary record supports the notion that humans evolved to be
vegetarians because we have flat molars and no sharp fangs, or who state
that "almost no primate ever eats meat."  I have heard fully qualified
medical doctors make statements like these, and heard the same from a
number of degreed dieticians and others promoting popular books on human
diet.

The fact that D'Adamo's book has been a bestseller in the United States
(and is apparently now being translated and sold in different countries)
indicates that there is much popular interest in this subject.  But it also
demonstrates that almost no one out there telling the public what really is
known (and not known) in this area.
 -=-
   The greatest mistake you can make in life is to be continually fearing
   you will make one.
                                           ---Elbert Hubbard (1859-1915)