fLUORINE,Arsenic, Cadmium, and Lead are essential micronutrients????
I suggest you refer to any good animal nutrition book (eg Macdonald
et al Animal Nutrition).
A micronutrient is a nutrient that is essential to the body, but it
is usually required in such minute quantities or are so widely
distributed in foods that deficiencies are occur rarely. Most of them
are very toxic if overconsumed. However, they are still essential. (A
silly analogy could be water essential too life, but too much could
cause death by drowning).
Flourine was added to the list of essential elements in 1972 when it
was shown that the growth rate of rats improved when small amounts
were added to a low flourine diet (This is a standard method for
testing since nutrition studies began in the early part of last
century). However it is a very toxic element as well.
Arsenic is widely distributed throughout the body especially in skin,
nail and hair. It has been shown to be essential for the rat, chick,
pig and goat. It is needed to form metabolites of methionine
including cystine (an amino acid in hair etc). Also extremely toxic.
The essentiality of Cadmium and lead are controversial, but it is
likely that the are essesntial in minute quantities. They are better
known however for their toxic qualities.
In summary the overall function of the microelements is that they are
responsible for enzymatic function as catalysts and co-enzymes. As
such they are essential. However, I must repeat that the likelihood
of defiencies is extremely low and ocurrences extremely rare
Hope this clears the mud
Dr MJ Linington
HEAD:Department Agricultural Sciences
Snail Mail: Dept. Agricultural Sciences
VUDEC, Vista University
P/Bag X641, Pretoria, 0001
Tel: 012 322 1303
Fax: 012 322 3243
cell:083 637 0182
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