melatonin

[ttweed@wildrockies.org (Tony Tweedale)]

_Science News_'s cover story on 17 Oct. ('Does Light Have a Dark Side?') is
very interesting--the conncetion between light and cancer.  As little as
0.2 lux (darker than a moonless night) leaked in under a door at night
caused tumors begun by another carcinogen to grow twice as fast in lab
annimals.  Light supresses melatonin hormone, and other studies have shown
that 50 lux (~a dimly lit room) of green light and 2,500 lux of white light
at 2am shuts down melatonin production in people.

Melatonin controls estrogen production, so it was thought long-term
disturbance of melatonin production at night is a cause of common breast
and other estrogen recepter cancers.  (EMF, in additon to light, depresses
melatonin).  But 3 large epidemeological studies seem to show suprressing
melatonin increases other cancers too, bny comparing cancers in blind and
sighted people.  In one, lung, colon, rectal, prostate, stomach, skin and
lung cancer in men; and breast, ovarian and stomach cancers in women were
reduced (overall, blind people had 70% the cancer of sighted people; while
in the 1st study, the blind had 1/2 as many)..  owever the latest study
only found the difference in breast cancer.

Sure, the naysayers will say that all this shows that synthetic endocrine
disrupting chemicals are a false scare.  To me, the other side of the coin
shines brighter--i.e. it shows how powerful hormones are.  There are too
many related observed peturbations in normal hormone function, and too many
studies showing the mechanisms by which hormones affect various functions
(e.g. various cancer rates, sexual development).  It would be easy to say
that natural light, as well as natural phytoestrogens and macrodoses of BGH
are the culprits, rather than synthetic chemicals  The truth is much more
that all these hormones are acting together, in concert and in opposition,
to disturb homeostasis, with persitent synthetic ones having a strong edge
that overcomes their smaller concentration.

Tony Tweedale

Causality is a concept not subject to empirical demonstration. -David Hume
(1711-'76)

Temperate but endangered planet.  Enjoys weather, northern lights,
continetal drift.  Seeks caring relationship with intelligent lifeform.
      -Friends of the Earth