Nutrition, vitamin Diets Food sources

The need to include a variety of minerals in experimental diets has already been mentioned this was especially stressed (1920-1930) by Boyd-Orr, the director of the Rowett Institute for Animal Nutrition in Scotland. Increasingly refined food sources led to the identification of large numbers of trace elements (e.g., Cu, Mn, Mo, Zn) whose importance in the diet was suggested from hydroponic experiments with plant seedlings. Cobalt is an example of such a trace element. Vitamin Bj2 is synthesized by bacteria in the rumens of sheep and cattle but is absent from their fodder. In Australia, sheep feeding on cobalt-deficient pastures failed to thrive because vitamin B12 could no longer be made. 

It is important to remember that healthy individuals can obtain sufficient vitamins and inorganic essentials from food sources in the normal diet. Unfortiuiately, many individuals fail to observe healthy eating patterns. A food pyramid has been suggested recently by the U.S. Department of Agricultme (http //www.mypyramid.gov/) as a template. Other fectors, such as lack of exercise, may result in nutritional deficiencies as well as diseases such as obesity, diabetes, and other chronic disorders. 

Sources. Niacin and substances that are convertible to niacin are found naturally in meat (especially red meat), poultry, fish, legumes, and yeast. In addition to preformed niacin, some L-tryptophan found in the proteins of these foods is metabolized to niacin. Niacin is also present in cereal grains, such as corn and wheat. However, consumption of corn-rich diets has resulted in niacin deficiency in certain populations. The reason for this is that niacin exists in cereal grains in bound forms, such as the glycoside niacytin, which exhibit little or no nutritional availability. Interestingly, niacin deficiency is not common in Mexico and Central America even though the diets of those in these countries are based on com. Alkaline treatment, such as soaking corn in a lime solution—the process used by the populations of Mexico and Central America in the production of com tortillas—yields release of bound niacin and increased availability of the vitamin. 

The DRI for pregnancy should be met for all vitamins and minerals. Medical food is the source of many vitamins and minerals in the maternal PKU diet however, if not taken as prescribed or if the medical food does not contain a full complanent of vitamins and minerals, intakes may be low. Vitamins and minerals that are of particular concern in maternal PKU are vitamin B,2 and folate [14]. Low intakes have been correlated with increased risk of CHD. Deficiencies in zinc, iron, and vitamin B12 may be seen in MPKU as these nutrients are most often found in high-protein foods that individuals with PKU do not usually consume. Prenatal supplements or specific vitamins and mineral supplementation may be necessary if monitoring of intake and/or if nutritional biomarkers indicate a problem. 

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