Zinc and mineral content of weight reducing diets.

The zinc content of four commonly used weight reduction diets and of three constant diets used for weight reduction in a Metabolic Research Unit was determined by atomic absorption spectroscopy. The diets were also analyzed for other elements, namely, for nitrogen, calcium, phosphorus, magnesium, and iron. The four commonly used weight reduction diets and two of the metabolic diets contained approximately 1000 cal, while one metabolic diet contained 600 cal. The zinc content of the diets correlated with the type but not with the amount of protein used because proteins of high biological value may have a low zinc content. There was no correlation between the zinc and calorie content of the diets. Although the protein content of two equicaloric diets was normal and similar, the zinc content differed by a factor of 2. Conversely, when the dietary protein was increased the dietary zinc content remained low, half of that of the RDA. Even when the diet contained only 600 cal the zinc intake was still approximately 75% of the RDA. The phosphorus and magnesium content correlated with the dietary protein. These studies have shown that the adequacy of the zinc and iron content of weight reduction diets depends on the type of protein used, however, there is no apparent correlation between the zinc and iron content of individual protein-containing foods.