On Thu, 16 Jul 1998, Don Wiss wrote:

> I gather you are referring to this study:
>
> Franceschi S, et.al; "Intake of macronutrients and risk of breast cancer"
> Lancet 1996;347(9012):1351-6
>
> They found the risk of breast cancer decreased with increasing total fat
> intake whereas the risk increased with increasing intake of available
> carbohydrates.

No, I don't think so.  I can't find the reference now but it was
specifically about colon cancer.

> This study was done in the Italian population which having a low awareness
> of diet and cancer issues there is less scope for recall bias. The feeling
> is in countries like the US the participates give biased answers based on
> what they think the surveyors want to hear.

I don't think this is an adequate explanation of the correlation
found in the non-Italian studies.  For one thing, it presupposes
that the participants in the study knew what correlations were
being looked for, so that people who got colon cancer would
think, "Hmmm, I guess they're trying to find out how much red
meat I ate."  But that's not how the studies were done.  They
were asked to answer questions about many facets of their medical
history and about their diet.  Nobody knew in advance what
correlations would be found.

Willett, who conducted the most recent of the studies, notes that
he was surprised that the correlation was as strong as it is (I
read an interview with him recently).  Even low levels of red
meat consumption were correlated with substantial increases of
colon cancer risk.  He concedes that no one yet has any very good
explanation of the reason for the correlation.  Some favor the
hypothesis that it has to do with the fat content, but at least
some of the studies show a correlation even after fat intake is
corrected for.

Since Ray's comments about the Samburu were only about their
cardiovascular health, given their high beef intake, I don't know
what their colon cancer rates might be.  Assuming for the sake of
the argument that they are low, we again must wonder if the
difference between them and those studied by Willett and others
is caused by a difference in the meat itself or a difference in
the people.  It seems that we don't yet have nearly enough
information to answer that one.

Todd Moody
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