Niacin index is calculated as NAD/NADP X 100. RBCs were lysed as described in the Methods outlined in the following kit manuals. To obtain the niacin index (NAD/NADP), the NAD/NADH quantification kit (Sigma-Aldrich Cat # MAK037) and NADP/NADPH quantitation kit (Sigma-Aldrich Cat # MAK038) were used in tandem. 10 µl of RBC samples were used for each kit according to manufacturer’s guidelines in a 96-well plate with included standards. Samples were filtered using a 10 kda MW cut off spin filter (ABCAM Cat # ab93349) spun at 20,000×g for 30 minutes. All colorimetric detection were accomplished using spectrophotometer absorbance at A = 450 nm. The niacin index and the NAD/NADH ratio were then calculated for each sample.