From: James Rogers (jamesr@best.com)
Date: Sun Nov 18 2001 - 11:11:19 MST
On 11/15/01 5:41 PM, "Colin Hales" <colin@versalog.com.au> wrote:
>
> In my childhood I read stories of the early settlers here (mid 1800s) who
> used to dab a bit of arsenic on their tongues to get themselves to be able
> to walk to the Ballarat goldfields from Melbourne(....75 miles) at a
> cracking pace.
Arsenic is a poorly understood element with respect to biology. It is
recognized as an essential micronutrient with many actions in the body, but
its general mechanisms are not known for the most part. Supplementation is
necessary in some locales and has been practiced for a very long time.
In some parts of the world, arsenic deficiency is a chronic problem due to
lack of local dietary sources and has traditionally been supplemented either
with arsenic rich food sources that have been imported or the mineral
itself, mostly to improve fertility and as a cure for wasting. Some
indications of arsenic deficiency are weakness, low weight, and infertility.
It is also thought to have beneficial activity in the cardiovascular system
and central nervous system, but these aren't well understood. Trace
quantities of arsenic have been added to animal feed for centuries to
improve animal health and weight.
The biggest source of arsenic in the human diet by far is meat, and seafood
in particular tends to contain large quantities of it. Ground water is the
number two contributor, but by itself does not contribute enough arsenic to
come close to meeting the proposed RDA for that mineral. Vegetable sources,
while frequently containing arsenic, often demonstrate poor bio-availability
for this mineral. Many plants have zero bio-availability, even though they
may contain enough arsenic to be extremely toxic (the arsenic is excreted in
the urine).
Which doesn't mean anyone should go around chowing down on arsenic, but the
toxicity of trace quantities has been highly overstated. Like chromium and
other micronutrients, an RDA has not been established yet. However, the
estimates for an arsenic RDA actually suggest a larger intake than for many
other minerals (e.g. several times larger than for chromium).
Cheers,
-James Rogers
jamesr@best.com
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