Changes in the Conversion Rate of Tryptophan-nicotinamide According to Dietary Fat and Protein Levels

The effects of dietary fat and protein levels on the conversion of Trp-Nam were investigated. In rats fed with 20% casein diets, the Trp-Nam conversion ratio [(urinary excretion of Nam + MNA + 2-Py + 4-Py in μmol/day)/(daily Trp intake during urine collection in μmol/day) × 100] was about 4.3% for the groups fed with the 20% corn oil and 20% soybean oil diets, 2.8% for the group fed with the 20% lard diet, and 2.1 % for the group fed with the no fat diet. In rats fed with 40% casein diets, a similar phenomenon was observed, but the ratios were 2.0%, 2.4%, 1.6%, and 0.8% for the groups fed with the 20% corn oil, 20% soybean oil, 20% lard, and no fat diets, respectively. From these results, it was found that an increase in fat intake elevated the conversion ratio regardless of the dietary protein level, while an increase in protein intake reduced it.