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diet, parasites and cancer

Mark Doherty mdoherty at pop.niaid.nih.gov
Mon May 12 10:39:44 EST 1997


In article <3374E066.B2 at iamerica.net>, cmonahan at iamerica.net (Cliff
Monahan) wrote:

> We are all in agreement that the herbalist hucksters have taken any
potential link to a 
> profitable extreme, but let's consider a moment that there may be some
link -- not 
> necessarily cause and effect -- between diet, parasites and cancer. Given
that 
> alterations in immune function can result in increased rates of infection
or a decline 
> in surveillance against tumors, the extreme being HIV infections leading
to all sorts of 
> sequelae, parasitic infections may be a signal that the immune response
has flagged for 
> some undetermined reason, and that tumor recognition may also be impaired.

For most of human history, parasitic infections have been the norm, not the
exception, so they certainly do not represent a failure of the immune
system.  Parasites have learned to live with our immune system - indeed,
many of them depend on our immune responses to complete their lifecycle. 
Interestingly, cancer rates are highest (or at least more commonly
diagnosed) in first world citizens, who tend to have low parasitism rates. 
In many parts of the theird world parasitism rates run close to 100%
without any noticeable increase in cancer rates.

> Diet may be a 
> factor, and, hypothetically, parasites may have evolved a mechanism
whereby they absorb 
> or metabolize a critical cofactor needed by the immune system for a
proper response and 
> expulsion of the parasite. If the parasites could alter the immune
response to 
> themselves, tumor surveillance may be affected as well.

This is an interesting idea, although I am unaware of any parasite that
actually does this.  However diet probably does play a role in cancer -
with various factors being related to different cancers.  For example, high
fibre diets appear to decrease your risk of lower bowel cancer, while
increasing your risk of stomach cancer.

>If this critical cofactor was a 
> dietary component, then supplementation beyond the metabolic capacity of
the parasite 
> burden may trigger an adequate response and expulsion of the parasites,
perhaps 
> resumption of tumor surveillance as well. Clearly, parasites are capable
of lots wierder 
> things in the host/parasite relationship, so let's not dismiss a
potential link through 
> a knee-jerk dislike of the herbalist fringe but consider it in a rational
and scientific 
> fashion.

Fair enough, but personally I'm not going to waste time, effort or money on
diet cures for a link to cancer for which no real evidence exists.  And
yes, I know some parasites *are* linked to some rare forms of cancer, but
as far as I know, I don't have those or any other parasites - nor does
anyone else of my acquaintance.  Finally, there are specific and very
effective cures for many parasitic infections.  If I *did* have one, that's
what I'd use - not some herbal potion of dubious relevance.

Cheers, Mark



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