MadSci Network: Biochemistry
Query:

Re: Phytate Interference With Mineral Absorption

Date: Tue Mar 14 17:06:43 2006
Posted By: Peter Bosani, Independent
Area of science: Biochemistry
ID: 1142030528.Bc
Message:

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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