Zinc absorption from composite meals II. Influence of the main protein source

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Abstract
The absorption of zinc in man from composite meals of conventional foods with various main protein sources was measured with a radionuclide technique. The meals were extrinsically labeled with 65Zn and the absorption of zinc was determined from a measurement of the whole-body retention of the isotope about 2 weeks after ingestion of the labeled meal. The meals consisted of a meat patty made from either chicken, beef, or soybeans, and included potatoes, tomatoes, and white bread. For meals based on animal protein a positive correlation was found between zinc absorption and zinc content. When 25% of the animal protein in the chicken meal was replaced by defatted soy flour neither the zinc content nor zinc absorption were significantly influenced. The same substitution in a beef meal resulted in a decrease in zinc content and also a lower zinc absorption. The absorption from a soybean meal did not differ from an animal protein meal with the same zinc content. Lower zinc absorption was found when the calcium content of a soybean meal was increased by the addition of milk. For this study, the total zinc content of the meal was the most important factor influencing the amount of zinc absorbed.