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

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.