On Fri, 28 Nov 1997, Bill wrote:

> It is interesting that the mammalian body produces saturated fats when
> faced with a surplus of calories.  Saturated fats are the bodies first
> choice.  I believe that the body could have learned to make unsaturated
> fats if they were in fact better for our survival over the long term.
> Remember that mammals have to store fat for years and decades, while
> plants only need the fat for a season or so (for energy for the
> seedlings).
>
> The whole issue of whether saturated fats are bad for you is clouded by
> the fact that people do not normally eat purely saturated or unsaturated
> fat.  Beef fat for example is about half saturated fat, and half
> unsaturated fat.

If beef fat is about half polyunsaturated (and it is, of course)
then either the animal is making unsaturated fat itself, or
storing the unsaturated fat that it eats.  That is, if saturated
fats are the body's first choice, we have to ask why beef fat is
only about half saturated.

> So if a study shows that people who ate more beef had
> a higher incidence of heart disease, or colon cancer, was it the
> saturated fat, or was it the unsaturated fat that made the difference?

First of all, the studies do not show a strong correlation
between fat and colon cancer (although until recently the
correlation tended to be blamed on fat).  It is something other
than the fat in red meat that is associated with colon cancer.

Second, it is not impossible to use factor analysis to separate
the correlations, and in fact this has been done.  That saturated
fat consumption is a risk factor for heart disease is strongly
supported by such analysis.  But that only *begins* to tell the
story.  It is also true that consumption of dairy products is
strongly correlated with heart disease and the markers for it.

So I don't think that all this means that people should not eat
saturated fats.  I do think it means that we have to look
carefully at the sources of those fats and at the ratios of
saturated, unsaturated, and monounsaturated fats.  Nuts and seeds
are rich in unsaturated fats, but also typically contain
antioxidants, which are removed when these oils are processed.

Also, when we read that a 5% increase in saturated fat intake
raises the risk of a heart attack by 17%, we have to interpret
that datum carefully.  It doesn't follow that it increases
*anybody's* risk by 17%.  It could be that for a substantial
number of people it causes little or no increased risk, but for a
smaller number of people it causes a significant increased risk.

We are biologically unique individuals.  Our response to various
diets is still quite unpredictable, and there is no reason to
believe that any particular way of eating is "safe" or "best" for
everybody, and that includes NeanderThin as well as the McDougall
diet.  Statistical analysis, epidemiology, and paleoanthropology
*cannot* tell us what is going on in our own bodies.  They can at
most give us hypotheses to test.

Todd Moody
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