Interrelationships between riboflavin and vitamin B6 among elderly people (Dutch Nutrition Surveillance System)

Vitamin B6 is considered to be a risk nutrient for elderly people. Conversion of most naturally available vitamin B6 to its functional coenzyme pyridoxal 5'-phosphate (PLP) depends on riboflavin. Therefore, interrelations were studied between riboflavin and vitamin B6 among 473 elderly people not using supplements containing B-vitamins. Habitual food consumption (assessed through dietary history with cross-check), plasma PLP levels and enzyme activities of erythrocyte glutathione reductase (EGR) and erythrocyte aspartate aminotransferase (EAST), with and without added flavin adenine dinucleotide and PLP, respectively, were determined. The results showed that unstimulated and stimulated EAST activity was higher when EGR activity (both simulated and unstimulated) was higher. Plasma PLP was positively associated with (un)stimulated EGR activities, but these correlations were not significant, probably due to the lower number of observations. Adjusted for the intake of vitamin B6 similar observations were made for the forementioned interactions between the biochemical indicators. To identify the strongest correlates of the vitamin B6 status indicators, stepwise regression analysis was carried out. The results showed that in each model an indicator of the riboflavin status was included. Our findings suggest an interaction between the status of riboflavin and vitamin B6 at intake levels normally found among Dutch elderly people.