vitamin requirements

New world requirements for vitamin A

NIJMEGEN, THE NETHERLANDS. Vitamin-A (retinol) is a fat-soluble
vitamin required to ensure proper function of the immune system and to
counteract the development of night blindness and weak eyesight; it
may also play an important role in cancer prevention. The current
Recommended Daily Allowance (RDA) in North America is 5000 IU or, more
correctly, 1000 RE equivalents for men and 4000 IU or 800 RE for
women. Children need between 400 and 700 RE daily depending on age.
Any intake above the daily requirement is stored in the liver. This
fact has led to cautions about taking too much vitamin A as it can be
toxic in large quantities. Vitamin A toxicity may occur in adults who
take more than 10,000 RE daily for several years. Pregnant women
should keep their daily intake below 1000 RE/day.
Vitamin A is obtained from the diet in two forms either as retinol
(from animal products) or in the form of carotenes (from fruits and
vegetables) which the body converts to retinol. In 1967 the World
Health Organization reported that it took six micrograms of
beta-carotene to produce one microgram (1 RE) of pure vitamin A. This
conversion factor has been used ever since to determine the average
daily vitamin A intake throughout the world. Using the WHO factor it
was estimated that the average daily vitamin A intake varied from
about 600 RE in South America and Asia to about 1000 RE in Europe and
North America. In other words, it's adequate in Europe and North
America, but deficient in Asia and South America.
Dutch and Indonesian researchers now report that the 1967 WHO
conversion factor is seriously wrong. Using up-to-date analysis
techniques and new information about bioavailability and bioconversion
of vitamin A and carotenes they conclude that it takes not six
micrograms of beta-carotene from fruits and vegetables to yield one
microgram of vitamin A, but rather 21 micrograms. This finding puts a
completely different complexion on things. Essentially, the entire
world is likely to be vitamin A deficient. The revised estimated daily
intake of vitamin A is now only 780 RE in Europe, 581 RE in North
America, 372 RE in South America, and a mere 258 RE in Asia where
blindness among children is becoming endemic.
The researchers urge further work to determine how to tackle this
massive problem. Editor's Note: This project obviously could take
years. In the meantime it would seem wise to supplement with cod or
halibut liver oil which are both excellent sources of vitamin-A and
vitamin-D.
West, Clive E. Meeting requirements for vitamin A. Nutrition Reviews,
Vol. 58, November 2000, pp. 341- 45

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Copyright 2001 by Hans R. Larsen
www.yourhealthbase.com
International Health News does not provide medical advice. Do not
attempt self- diagnosis or self-medication based on our reports.
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