Читать книгу Pathy's Principles and Practice of Geriatric Medicine - Группа авторов - Страница 347

Calcium is related to bone health and is a risk nutrient in elderly people with no or little dairy products in their diet. This can be the case in many cultures and was particularly observed in some Asian centres. It is not, however, specifically an age‐related problem.

Zinc deficiency is seen in older people, particularly among diabetics. Zinc is available widely in foods, but the bioavailability is better from animal than plant foods. In whole‐grain products, phytates may inhibit the absorption of zinc. Red meat, seafood, fresh fruit, vegetables, and dairy products are the primary sources. Zinc is involved in protein synthesis, nucleic acid synthesis, and gene regulation. Further, it is part of several enzymes. Biochemical abnormalities of zinc deficiency include a reduction in plasma zinc concentrations, protein synthesis, activity of metalloproteins, resistance to infection, collagen synthesis, and platelet aggregation. Other manifestations of zinc deficiency are anorexia due to impaired taste and smell, impaired vision, confusion and restlessness, and sometimes diarrhoea. Zinc measurements are often problematic. Cytokines dramatically reduce serum zinc. Leukocyte zinc levels or zinc hair levels, when determined properly, may be useful.

Iron has special nutritional interest because of the high incidence of iron deficiency worldwide in younger age groups. Iron is available in many foods in small amounts, but bioavailability differs considerably between foods. Two broad categories of iron are present in food: heme iron derived mainly from animal foods and non‐heme iron in plant foods. Heme iron is much better absorbed. Because of this difference in bioavailability, dietary recommendations vary according to the nature of the diet. These recommendations are difficult to meet in plant‐based diets solely due to the lower bioavailability of plant‐based iron. However, the requirement is sharply reduced in postmenopausal women, and their iron status is correspondingly improved. Adult men generally have no problem meeting their iron requirement. When anaemia is diagnosed, chronic blood loss or deficiency of folate or vitamin B12 should be considered. In the elderly using multivitamin mineral supplements with iron, there is concern about iron overload rather than prevention of deficiency. Serum iron together with ferritin is readily available to determine free and storage status. In some cases, measuring soluble transferring receptors may be useful.