Figure 8.

Urinary concentrations of the vitamers of vitamin B₃, (A), nicotinic acid, (B), nicotinamide, and (C) nicotinuric acid at baseline (pre) and after (post) supplement ingestion in older and younger adults. Bar plots and error bars represent means and ± SEM respectively, n = 20 in each age groups and concentrations are normalized for urinary creatinine (nmol/mmol creatinine). Data for pre and post supplement ingestion was compared using generalized linear repeated measures analysis of variance with time as within subject and age as between subject factor. Sidak post hoc test was applied for pairwise comparisons in case of an interaction. There were no interactions between any independent factors (age and time). There were main time effects (*, p < 0.05; **, p < 0.01; ***, p < 0.001) for all the vitamers and a main age effect for nicotinic acid (**, p = 0.007).