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From: B. Harris)
Subject: Re: Carotenes Block Cancer Cell Division(Fwd]
Date: 16 Apr 1998 23:54:34 GMT

In <>
(Danny Cox) writes:

>---- Begin Forwarded Message
>  Frank Grazian, Alternative Health News Online
>ITHACA, N.Y. -- A common chemical derivative of vegetables has been used
>by Cornell University researchers studying leukemia to block the
>uncontrolled cell division that leads to cancer.
>The chemical is retinoic acid, a product of vitamin A, which the body
>manufactures from carotenes, the compounds found in a wide assortment of
>yellow-orange vegetables and fruits, from carrots and sweet potatoes to
>pumpkins and apricots.


    Good grief-- another article reported by the papers as hot news,
which is work of a type that has been done for decades, and on which
there must have been literally thousands of papers written by now.  It
has been known that retinoic acid causes cell differentiation since
1925, and cancer inhibition since probably before I was born.  The
research in question, of course, simply relates to mechanistic details
of HOW this happens.  It's not news that it happens.

    Retinoic acid, BTW, for those interested, is the form of vitamin A
which does most of the functions of the vitamin (with the exception of
the retinal/visual function and some reproductive functions).  It's a
very hormone-like molecule which binds to a cell nuclear receptor in
the manner of steroids, thyroid hormones, and 1,25 vitamin D.  It's
what supports growth and health and many membrane functions as well.
If nothing but retinoic acid is given to animals, they can't reproduce,
and they eventually go blind from loss of retinal cells, but otherwise
they're fine.  They don't get the dry eyes or corneal ulceration that
causes blindness in vitamin A deficient HUMAN populations-- it's a
different problem.  The anti-infective properties of vitamin A in
deficient populations are also no doubt related to its retinoic acid

   Retinoic acid can't be converted to other kinds of vitamin A (the
reverse is not true, however), and retinoic acid can't be stored.  It's
sort of the end product.  Whether or not you can get more of it in your
body by eating more beta carotene, or whether you'd want to, is a
little iffy.  Many scientists have long suspected that it's the major
anticancer metabolite in the vitamin A series, but there's massive
evidence on both sides, and I'm not going to go into it.  Retinoic acid
is also certainly the metabolite that causes all those symptoms of
vitamin A poisoning, many of which have to do with cells
differentiating and shutting down when they aren't supposed to.  If you
eat polar bear liver, the skin of your hands and other places comes off
in giant sheets...   That's too much retinoic acid.

   It's worth commenting that 13 cis retinoic (Accutane) acid and some
other vitamin A derivitives which have been used on leukemias and
epithelial cancers for some years, are basically more pharmaceutically
powerful forms of retinoic acid.  Their powerful teratogenic effects
are related to their ability to foul up natural hormonal functions of
retinoic acid in the embryo.  There are some times when you don't WANT
things to differentiate (yet).

                                        Steve Harris, M.D.

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