Efficiency of Conversion of Tryptophan to Niacin in Humans

Nakagawa, Itsiro; Takahashi, Tetsuzo; Sasaki, Atsuko; Kajimoto, Masatoshi; Suzuki, Taeko

doi:10.1093/jn/103.8.1195

Cited by 12 publications

(5 citation statements)

References 8 publications

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“…Also included in this RNI is the contribution of niacin derived from the endogenous conversion of tryptophan to niacin in the ratio 60:1, giving a stated requirement for niacin or nicotinic acid equivalents. Whilst it is suggested that tryptophan to niacin conversion alone may satisfy vitamin B 3 requirements, based on assessments of dietary protein intakes ( 82 ) , the conversion ratio is dependent on the intake, and relative availability of, multiple nutrient factors, including the availability of all other relevant cofactors (for example, pyridoxine) ( 132 ) . The study of Hokwitt et al ( 131 ) included only three elderly subjects who were reported as sedentary.…”

Section: Niacin (Vitamin B3)mentioning

confidence: 99%

Selected B vitamins and their possible link to the aetiology of age-related sarcopenia: relevance of UK dietary recommendations

2018

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The possible roles of selected B vitamins in the development and progression of sarcopenia are reviewed. Age-related declines in muscle mass and function are associated with huge and increasing costs to healthcare providers. Falls and loss of mobility and independence due to declining muscle mass/function are associated with poor clinical outcomes and their prevention and management are attractive research targets. Nutritional status appears a key modifiable and affordable intervention. There is emerging evidence of sarcopenia being the result not only of diminished anabolic activity but also of declining neurological integrity in older age, which is emerging as an important aspect of the development of age-related decline in muscle mass/function. In this connection, several B vitamins can be viewed as not only cofactors in muscle synthetic processes, but also as neurotrophic agents with involvements in both bioenergetic and trophic pathways. The B vitamins thus selected are examined with respect to their relevance to multiple aspects of neuromuscular function and evidence is considered that requirements, intakes or absorption may be altered in the elderly. In addition, the evidence base for recommended intakes (UK recommended daily allowance) is examined with particular reference to original datasets and their relevance to older individuals. It is possible that inconsistencies in the literature with respect to the nutritional management of sarcopenia may, in part at least, be the result of compromised micronutrient status in some study participants. It is suggested that in order, for example, for intervention with amino acids to be successful, underlying micronutrient deficiencies must first be addressed/eliminated.

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Section: Niacin (Vitamin B3)mentioning

confidence: 99%

Selected B vitamins and their possible link to the aetiology of age-related sarcopenia: relevance of UK dietary recommendations

2018

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“…This approach has been consid ered to be unsatisfactory. Nakagawa et al [14] have observed that the excretion of nic otinic acid metabolites is greatly influenced by the body stores of nicotinic acid and tryp tophan. These authors have concluded that it is difficult to determine the efficiency of tryp tophan-substituting nicotinic acid for its coenzyme synthesis on the basis of the amount of nicotinic acid metabolites ex creted.…”

Section: Resultsmentioning

confidence: 99%

In vivo Conversion of Tryptophan to Nicotinic Acid in Rats Studied by Simultaneous Incorporation of [<sup>3</sup>H]-Tryptophan and [<sup>14</sup>C]-Nicotinic Acid into Liver NAD and NADP

Satyanarayana

Rao²

1983

Ann Nutr Metab

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This study was carried out with three groups of weanling rats. One group was fed a high-protein (20%) diet, another group a low-protein (2.5%) diet, the third group a high-protein diet in restricted amounts. After 4 weeks of feeding, rats were injected simultaneously with L-[G-³H]-tryptophan and [carboxyl-¹⁴C]-nicotinic acid. The ratio of incorporation of [³H]-tryptophan to that of [¹⁴C]-nicotinic acid into liver NAD and NADP was found to be higher in protein-restricted rats. On the other hand, the ratio was found to be reduced in diet-restricted group of rats compared with ad libitum fed or low-protein diet fed groups. These results suggest that the efficiency of conversion of tryptophan to NAD is increased in protein deficiency, but reduced in the diet restriction. These observations are in line with our earlier findings on the changes in liver quinolinate phosphoribosyltransferase (EC 2.4.2.19) activity following feeding of low-protein or restricted diets. It is suggested that this technique of measuring the incorporation of two isotopes from the substrates labelled with two different isotopes can be conveniently used as a tool to measure the relative contribution of tryptophan and nicotinic acid to the synthesis of nicotinamide nucleotides.

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“…We found that niacin intake levels were insufficient in all regions. However, as our dietary intake calculation did not take into account intake of tryptophan, which can be converted to niacin in the body [96][97][98], we may have overestimated the niacin inadequacy. Similar findings have been observed in other studies [99][100][101][102], showing that achieving the estimated average requirement, especially for zinc and iron, is difficult in young children.…”

Section: Young Child Nutritionmentioning

confidence: 99%

“…Home fortification of complementary foods with MNPs has several advantages: it does not require major changes in dietary practices, allows the child to get a full dose of the required micronutrients by mixing it in a small quantity of food, is better accepted than medicinal iron drops and less expensive than fortified complementary foods [95]. In addition, the iron absorption of supplements is better than that of fortified foods [96]. Combined supplementation (iron and vitamin A) has been found to be more effective than single supplementation [97].…”

Section: Pros and Cons Of An Intervention With Mnpsmentioning

confidence: 99%

Optimizing young child nutrition in Ethiopia : the effectiveness, acceptance and risks of micronutrient powders

Hafebo

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Ageappropriate infant and young child feeding practices are associated with child nutrition in India: insights from nationally representative data. Matern Child Nutr. 2015;11(1):73-87. 28. WHO. Global strategy for infant and young child feeding. Geneva: World Health Organization; 2003. 29. WHO/UNICEF. Complementary feeding of young children in developing countries: a review of current scientific knowledge.

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Efficiency of Conversion of Tryptophan to Niacin in Humans

Cited by 12 publications

References 8 publications

Selected B vitamins and their possible link to the aetiology of age-related sarcopenia: relevance of UK dietary recommendations

Selected B vitamins and their possible link to the aetiology of age-related sarcopenia: relevance of UK dietary recommendations

In vivo Conversion of Tryptophan to Nicotinic Acid in Rats Studied by Simultaneous Incorporation of [<sup>3</sup>H]-Tryptophan and [<sup>14</sup>C]-Nicotinic Acid into Liver NAD and NADP

Optimizing young child nutrition in Ethiopia : the effectiveness, acceptance and risks of micronutrient powders

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