Approximately 40 nutrients are required by the human body, Nutrients are essential if they cannot be synthesized by the body and if a deficiency causes recognizable abnormalities that disappears after the correction of deficiency. Required nutrients are amino acids, water soluble vitamins, fat soluble vitamins. Minerals and essential fatty acids etc. the body also requires an adequate energy substrate, a small amount of metabolize carbohydrate, indigestible carbohydrate (Fiber), additional nitrogen and water.
Nutritional requirements have been most commonly expressed by recommended dietary allowances food and nutrition board of the national academy of science, the RDA’s were initially designed to meet the known nutritional needs of practically all healthy persons. RDA’s have been established for energy and protein. The water soluble vitamins B12 and vitamin C the fat soluble vitamins A, D and K and the minerals calcium, phosphorus, Magnesium, Iron, zinc, lodine and selenium.
Recently the food and nutrition board has developed a broader approach to define nutritional adequacy known as dietary reference intakes (DRIs), these new guidelines go beyond the prevention of classic nutritional deficiency disease and address the role of nutrition and other food components in long term health and reduction of risk of chronic diseases. The DRI’s consists of four references intakes; the RDA, the estimated average requirement (EAR), the tolerable upper link leel (UL) and the adequate intake (A1). The RDA remains the dietary intake that is sufficient to meet the nutritional requirements of nearly all individuals in an age and gender specific group. The RDAs are intended as goals for individuals, the EAR is the intake value that is estimated to meet the requirements of 50% if individuals in an age and gender specific group. The UL is the maximum level of daily nutrients that is unlikely to pose health risks to meet individual. The A1 is determined when insufficient data are available to establish the EAR and RDA for given nutrient.