CH1 OF NUTR.pdf - The biological need for nutrients or...

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The biological need for nutrients, or homeostatic hunger, manifests as an acute physical feeling that is triggered by the orexigenic pathways in the hypothalamus, sensing low levels of circulating nutrients, and the empty stomach hormone, ghrelin. This internal feedback stimulates food intake. Following a satisfying meal, the stomach and fat tissues release several counter regulatory hormones that stimulate the anorexigenic neural pathways, which in a healthy adult, ceases the desire to eat.
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If the human nutrition system were impermeable to the persisting psychosocial needs that drive appetite after an individual's biological needs have been satisfied, and if an ample variety of only wholesome nutritious foods were consistently available, then a person's natural food intake would match their basic nutrient needs, and nutrition guidelines could be developed simply by measuring the weight and nutritional composition of someones natural food intake. However, because our foods are not limited to those that are wholesome and nutritious- rather, they are supplied in ample quantities in forms just the opposite, nutrition researchers and professionals have been challenged to determine the optimal daily intake level for each of the major nutrients and also to promote those levels to specific and targeted individuals in the population. The amount of food and level of nutrients that are needed to satisfy homeostatic hunger has been quantified in laboratory studies and clinical trails as well as in epidemiological research. In these investigations, nutrition-related biomarkers are measured across different diets and populations to generate thresholds for recommended minimum and maximum daily intake levels that are shown to contribute to optimal bodily systems outcomes. Data from such trials has been collected, reviewed and published by the Institute of Medicine (IOM) in the over 3,000-page Dietary Reference Intakes (DRI) report. The DRI report includes research data summaries for more than 30 nutrients that are consumed in the human diet. The report includes details about each nutrient’s average intake in the population and significant dietary sources, and for 19 of the nutrients in the report with substantial scientific evidence, explanations of human bodily processing and theoretical models that rationalize the recommended daily intake levels. Findings for this group of nutrients are reduced to a small
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set of reference values that are presented in several summary tables that are sectioned by the major nutrient classes and demographic groups. The most well-known value in the DRI is the Recommended Daily Allowance (RDA). The RDA is the range of nutrient intake that is adequate to meet the physiological needs of about 97% of the Nation's population, and it is the basis for nutrition-related claims on foods as well as targets for feeding assistance programs. The RDA is generated using the variance in the data sets that were used to develop the lesser-known Estimated Average Requirement (EAR), which is the median daily intake estimated to meet the needs of approximately half the population.
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