Re: Arsenic and cattle

On Wed, 15 Feb 2006 06:13:44 -0700, "N:dlzc D:aol T:com \(dlzc\)" <N:
dlzc1 D:cox T:net@xxxxxxxxxx> wrote:


I had made an unsupported statement about a year
and a half ago that cattle required a small amount
of arsenic in their diets to survive. I was asked for
any sort of literature support and found very little at
the time.

http://www.ead.anl.gov/pub/doc/arsenic.pdf
"Depending on the amount ingested, arsenic can
be beneficial (animal studies suggest that low
levels of arsenic in the diet are essential) or
adverse (high levels can be toxic)."

http://horse.purinamills.com/bulletins/poison/lamenessinducing.html

"The toxic effects of selenium in ruminants
varies, depending on the amount and rate of
its absorption, the individual animal's
susceptibility, the type of selenium present in
the plant, and the interaction of selenium with
other elements, such as sulfur, arsenic, or
copper, in the diet. These minerals, and
possibly others, competitively interfere with
selenium absorption by ruminants. If this
also occurs in horses, adequate amounts of
these minerals in their diet may help reduce
selenium poisoning for them, although
currently this hasn't been demonstrated."


I did a little more looking, and the situation does not become
clearer. The common statements are that As is not essential for
plants, seems to be essential for some animals, and it is not known
for sure with humans. There is nothing particularly wrong with this
ambiguity. Demonstrating that a micronutrient is truly essential, at
levels commonly encountered, is not easy -- especially for humans. The
possibility that it might act to counter something else is a possible
confounder, that can make something non-essential appear essential
under the tested conditions. It helps if a reason for essentiality is
found, and apparently that bar has not been reached for As. Someone
noted a relationship to methionine metabolism. Yes, but the
essentiality of that is not at all clear.


Here are a few more links, for those who want to look:


American Chemical Society:
http://pubs.acs.org/cen/80th/arsenic.html
The status of arsenic changed in 1987 when inorganic arsenic present
in drinking water was classified as carcinogenic. Arsenic is known to
be nonessential for plants but an essential trace element in several
animal species, while its presence in humans is an issue of debate.


EPA (US):
http://www.epa.gov/ttn/atw/hlthef/arsenic.html
Some studies have suggested that inorganic arsenic is an essential
dietary nutrient in goats, chicks, and rats. However, no comparable
data are available for humans. EPA has concluded that essentiality,
although not rigorously established, is plausible. (1,6)


Journal article on determining trace element needs. This one does
accept As as beneficial. Link here is to PubMed. I have included the
abstract below.
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=8811801&query_hl=10&itool=pubmed_docsum

J Nutr. 1996 Sep;126(9 Suppl):2377S-2385S. Related Articles, Links

How should dietary guidance be given for mineral elements with
beneficial actions or suspected of being essential?

Nielsen FH.

U.S. Department of Agriculture, Agricultural Research Service, Grand
Forks Human Nutrition Research Center, North Dakota 58202, USA.

The term ultratrace elements, often used to indicate elements with an
established, estimated or suspected requirement generally indicated by
microgram/, could be applied to at least 20 elements. The quality of
experimental evidence for nutritional essentiality varies widely for
the ultratrace elements. Thus, although differing dietary guidance is
appropriate for these elements, most need increased attention in
future editions of the Recommended Dietary Allowances (RDAs) for the
following reasons: (1) Increased interest in these elements by the
public has been stimulated by the mass media; thus, responsible
information about the usefulness of the ultratrace elements for health
and well being is needed. (2) Risk assessments and toxicological
standards are influenced by the RDAs. Authorative advice is required
to prevent standards that obstruct the achievement of beneficial
intakes of ultratrace elements. (3) An emerging new paradigm is that
the determination of nutritional requirements should include
consideration of the total health effects of nutrients, not just their
roles in preventing deficiency pathology; some of the ultratrace
elements have identified health benefits. Six ultratrace elements,
iodine, selenium, manganese, molybdenum, chromium and boron (and
cobalt as vitamin B12), merit specific RDAs. The term "estimated safe
and adequate daily dietary intakes (ESADDI)" should not be used for
any of the other ultratrace elements because of the misleading words
"adequate" and "safe". "Apparent beneficial intake (ABI)" seems more
appropriate for the elements with beneficial, if not essential,
actions that can be extrapolated from animals to humans; these
elements include arsenic, fluoride, lithium, nickel, silicon and
vanadium. The evidence is too limited or controversial for the
remaining ultratrace elements to even provide an ambiguous ABI. The
amount found in a healthful diet probably should be a value provided
for an appropriate intake for aluminum, bromide, cadmium, germanium,
lead, rubidium, and tin.



More recent journal article. Seems to make no mention of possible
benefit of As -- though that may have been outside their purview.

PubMed link:
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=12730460&query_hl=6&itool=pubmed_docsum

1: J Nutr. 2003 May;133(5 Suppl 1):1536S-8S. Related Articles, Links

Health effects and risk assessment of arsenic.

Abernathy CO, Thomas DJ, Calderon RL.


Fun. Maybe there will be an answer someday.

bob
.

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