Riboflavin 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. 

In conclusion, we have found that the presently set Recommended Dietary Allowances for riboflavin for women are inadequate even when they are not exercising, and that their riboflavin requirements are Increased by exercise. Weight reduction per se does not have an effect on riboflavin requirements. However, women who are exercising and on a weight reduction diet may get an inadequate amount of the vitamin because of their restricted food intake. We have no evidence, at least in the U.S., that athletes are at risk for clinical riboflavin deficiency. We do not think that it is necessary for those engaged in exercise to take megadoses of this B vitamin or of other B vitamins. 

An example of the difference between the AI and the EAR is provided by riboflavin. Very few data exist on the nutrient requirements of very young infants. However, human milk is the sole recommended food for the first 4 to 6 months, so the AI of the vitamin riboflavin for this life stage group is based on the amount in breast milk consumed by healthy full-term infants. Conversely, the riboflavin EAR for adults is based on a number of studies in humans relating dietary intake of riboflavin to biochemical markers of riboflavin status and development of clinical deficiency symptoms. 

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. 

The recommended riboflavin requirements for humans vary with respect to sex, age, and physiological state (such is the case during pregnancy and lactation). Normal adults need to consume between 0.9 and 1.6 mg of this vitamin on a daily basis since the human body does not have deposits of riboflavin and an excess of vitamin intake is eliminated in urine (Institute of Medicine 1998). Although present in a wide variety of foods, riboflavin deficiency (ariboflavinosis) still occurs in both developing and industrialized countries (O Brien et al. 2001 Blanck et al. 2002). Even though severe cases of ariboflavinosis are not common in most societies, subclinical manifestations are frequent and these are only detectable by measuring the blood vitamin concentrations. 

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