Niacin vitamin requirements/recommendations

Vitamins are chemically unrelated organic compounds that cannot be synthesized by humans and, therefore, must must be supplied by the diet. Nine vitamins (folic acid, cobalamin, ascorbic acid, pyridoxine, thiamine, niacin, riboflavin, biotin, and pantothenic acid) are classified as water-soluble, whereas four vitamins (vitamins A, D, K, and E) are termed fat-soluble (Figure 28.1). Vitamins are required to perform specific cellular functions, for example, many of the water-soluble vitamins are precursors of coenzymes for the enzymes of intermediary metabolism. In contrast to the water-soluble vitamins, only one fat soluble vitamin (vitamin K) has a coenzyme function. These vitamins are released, absorbed, and transported with the fat of the diet. They are not readily excreted in the urine, and significant quantities are stored in Die liver and adipose tissue. In fact, consumption of vitamins A and D in exoess of the recommended dietary allowances can lead to accumulation of toxic quantities of these compounds. 

The individual vitamin demand varies widely and is also dependent on the personal constitution. Stressful situations and e.g. pregnancy require a higher vitamin intake. For men, the recommended daily dose of Vitamin A, Bj, B2, Bg, K and niacin is usually higher than for women. There are series of studies, which confirm the breadth of application and the tolerability of vitamins and other micronutrients. The pharmacological effects with high doses of antioxidant provitamins and vitamins (especially )S-carotene and Vitamins C and E) in the treatment of cardiovascular and other diseases have been encouraging, albeit further controlled clinical studies will be needed to substantiate these observations. 

NOTE WELL The Food and Drug Administration requires that fortified foods or foods that are labeled or advertised with a claim to their nutrition be labeled to show content, in terms of percent Recommended Daily Allowance, of protein, vitamin A, vitamin C, thiamin, riboflavin, niacin, calcium, and iron. Also, serving size and quantities per serving must be stated for calories, fat, protein, and carbohydrate. 

Vitamins, minerals, and electrolytes— Studies have shown that during moderate to severe stresses, more zinc, copper, magnesium, and calcium are lost in the urine. Furthermore, stress results in altered blood levels of vitamins A and C, and of zinc and iron. Also, part of the response to stress includes water and sodium retention, via veisopressin and aldosterone secretion. As for the water-soluble vitamins—thiamin, riboflavin, niacin, pyridoxine (B-6), pantothenic acid, folic acid, and vitamin C stress increases their requirement. However, no dietary recommendations are made for these nutrients for individuals under stressful situations. Still, it seems wise to supply some supplementation before deficiency symptoms appear. 

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