Riboflavin adequate intake

Vitamins occur naturally in many foods and raw materials. However the natural contents are often supplemented in many food products to ensure an adequate intake, for example in infant formulae, breakfast cereals and clinical nutrition products. Vitamins are usually added as nutrients and thus not covered in this chapter but may also be added as food colours (riboflavin, carotenes). The reader should refer to the following references for recent developments in... 

Table 6.2 Recommended Dietary Allowances and Adequate Intakes of riboflavin."...

Patient with second- and third-degree burns excrete twice the normal intake of riboflavin. It is assumed that the increased excretion results from decreased use. Although the cause of such decreased use is not known, it has also been suggested that the massive nitrogen loss that occurs in extensive bums is responsible for the decreased vitamin consumption. When the bums heal, amounts of riboflavin greater than normal are needed to promote adequate cellular restoration. 

Although the nutritional aetiology of pellagra is well established, and tryptophan or niacin will prevent or cure the disease, additional factors, including deficiency of riboflavin (and hence impaired activity of kynurenine hydroxylase) or vitamin (and hence impaired activity of kynureninase), may be important when intakes of tryptophan and niacin are only marginally adequate. 

The synthesis of riboflavin, like thiamin, was observed in various animals. In the rat the site of synthesis seems to be the colon (25, 26, 40). When synthesis of riboflavin is increased the requirement of the rat for the vitamin diminishes. In the rumen of sheep (49) there is even greater synthesis. The rumen contents showed a riboflavin value about one hundred times that of the feed used (68, 69). In the cow marked synthesis also takes place (51, 52, 53, 68). The daily output of riboflavin in the milk alone was found to be ten times the intake (68). This impressive amount of synthesis affords adequate explanation for the observation that the riboflavin content of the ration of the cow (70) and goat (71) does not appreciably alter the amount of riboflavin secreted in the milk. Riboflavin synthesis also occurs in the feces of fowl, particularly after passage (72) from the body. 

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