Bioavailability of essential trace elements from meat

Summary from the Meat Information Service from Germany - Edition 04-2004

In nutritional research, the term "bioavailability" describes the extent and speed with which a nutrient becomes available for its normal physiological functions in the organism after consumption. This depends on its release from the diet, its structure (some nutrients exist in multiple species with different chemical structures), and its absorption and distribution. Meat and meat products are not only rich in certain vitamins and trace elements, the bioavailability of the nutrients from meat is often higher than from foods of plant origin. This applies, for example, to the trace elements iron, selenium and zinc.

Iron is an essential, i.e. vital, trace element for the human body. Inadequate iron supply with low iron stores is found primarily in children, adolescents and women of childbearing age. Depending on the chemical structure of the iron compounds in food, a distinction is made between non-heme iron from plant foods and heme iron from animal foods. Since iron from heme iron can be absorbed about two to three times better than from non-heme iron, the organism has significantly more iron available when eating meat and fish than when consuming food of non-animal origin. At the same time, certain substances in meat promote the absorption of non-heme iron from plant foods. On the other hand, various plant compounds such as phytates from cereals and legumes and polyphenols from fruit, vegetables, cocoa and wine inhibit iron absorption. With a skilful composition of the diet, with an appropriate proportion of meat and meat products, an iron deficiency can be avoided or compensated.

The essential trace element selenium, as a component of functional proteins, is also of fundamental importance for human health. Its effectiveness is based on the fact that it can intercept highly reactive oxygen compounds and render them harmless. In the past ten years, extensive analyzes of more than 1.500 foods from Central Europe have been presented. Foods of animal origin were generally found to be rich in selenium. Vegetable foods, on the other hand, were low in selenium with a few exceptions. Due to the abundance of possible influencing factors, the selenium bioavailability from food is difficult to determine. Therefore, the results of animal experiments are mainly used. So could e.g. For example, in rats with a selenium deficiency, it was shown that the empty selenium stores were replenished best and fastest when pork was added to the feed as a source of selenium - followed by beef, chicken, veal and lamb. Further studies confirm that selenium from a food of animal origin is particularly readily available and in this respect clearly surpasses a number of foods of plant origin.

The importance of zinc in the organism is based on the fact that it is a component and cofactor of more than 300 enzymes, acts as a stabilizer of biological membranes and is a component of DNA-binding proteins. Most of the zinc in food is bound. These usually very stable complexes must first be digested in the intestinal tract before the zinc can be absorbed. Phytates are the main inhibitors of zinc absorption. They greatly impair dietary zinc absorption. The bioavailability of zinc thus depends crucially on the phytic acid content of the food consumed. Meat and meat products themselves contain zinc in a readily available form and also increase zinc absorption from plant-based foods. The superiority of meat over plant-based foods in terms of promoting the bioavailability of zinc for humans has been demonstrated in various studies.

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Source: University of Giessen [ Prof. Dr. Irmgard M. Bitsch, Institute for Nutritional Science ]