MadSci Network: Biochemistry |
Hello Matthew,
It's true that phytates can reduce the absorption of minerals. Phytic
acid lies just underneath the grain's seed coat. There have been
documentated cases where diets low in minerals and high in fiber have
produced symptoms of disease, for example in Dublin, during W.W.II, and in
poor regions of Egypt and Iran.
It's important to note that it was a combination of both factors that
caused disease.
In reality, a high fiber diet's ability to bind minerals is minimal, especially if you're eating a diet rich in minerals. It turns out, foods naturally high in fiber are themselves rich in nutrients, including minerals, when compared to refined or processed foods. The body also adapts to higher phytic acid levels by slowing down the binding and excretion of minerals, according to a USDA study in 1987.
It's best to be safe and stick to the recommended 25 to 35 grams of fiber a day, from both soluble and insoluble sources.
Aside from Popeye, iron supplements are not necessary for adult men that
consume at least 2,000 calories a day. You'll get all the iron you need,
and since males don't normally bleed, iron tends to get stored up in the
body.
By age 50, the average American man has enough iron stored to live 4 years
without additional dietary iron, let alone supplements. Although iron
toxicity is rare, it can and has occurred.
About 5% of the European/Anglo Saxon population carries the gene for
hemochromatosis unknowingly. Symptoms often don't appear until the ages
of 40 to 60. Iron stores are built up to toxic levels that can cause
serious damage to organs, mostly the liver and pancreas. This occurs 5 to
10 times more frequently in males. Iron supplementation is obviously
contraindicated in this population.
Dr. Saul Hendler of the University of California in San Diego, who also
served as nutritional adiviser to the U.S. Olympic Committee, likewise
does not generally recommend iron supplements for men. Such
supplementation can mask anemias, deficiencies, or disease processes that
require medical attention.
However, for groups who need to supplement, Dr. Hendler suggests iron be
taken by itself, or with Vitamin C, between meals for maximum absorption,
except for a form known as carbonyl iron, which is to be taken with
meals. Amounts should range between 10 to 15 mg. a day, and not exceed
it, unless under doctor's orders. Ferrous sulfate is the most
bioavailable form.
Iron levels can easily be increased through diet by cooking in iron pots or skillets, eating foods rich in iron, and serving them along with Vitamin C containing foods.
Zinc has a better safety profile than iron does for men. However, it can interfere with copper absorption, even when supplementing with doses as low as 25 mg. a day, when taken over a long period of time. This can eventually cause anemia. Doses of 20 mg. or less are unlikely to present with problems. Zinc supplements are best taken with meals.
A few final suggestions - remember to eat fiber within the recommended
range, and don't take your supplements with tea or coffee, as both can
interfere with iron absorption.
Rather than take supplements in isolation, it is safer to take a well-
balanced vitamin/mineral formula containing all the nutrients.
This lowers the risks of megadose supplementation or adversely affecting
the proper balance between minerals and vitamins. Such formulations are
best taken with meals.
Hope that helps.
Peter Bosani.
Bibliography: The Doctors' Vitamin and Mineral Encyclopedia - S. Hendler
Publisher - Fireside 1991
The Wellness Encyclopedia of Food and Nutrition -
University of California at Berkeley - Publisher - Rebus - 1992
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