Comparative vitamin B-6 bioavailability from tuna, whole wheat bread and peanut butter in humans

Relative bioavailability of vitamin B-6 from tuna, whole wheat bread and peanut butter was investigated in eight men. The study was divided into a 10-day adjustment and three, 14-day experimental periods in a 3 X 3 Latin square design. Vitamin B-6 intake was set at 1.6 mg/day, with 50% of the intake coming from one of the three experimental foods and 50% from a basal diet. Daily complete urine and fecal collections were made. Urine was analyzed for 4-pyridoxic acid (4PA) and vitamin B-6, fecal samples for vitamin B-6 and plasma (sampled every 5 days) for pyridoxal 5'-phosphate (PLP). Mean values +/- SD for the adjustment, tuna, whole wheat bread and peanut butter periods were: 5.65 +/- 1.76, 4.89 +/- 1.10, 3.62 +/- 0.66 and 2.80 +/- 0.50 mumol/day for 4-pyridoxic acid; 0.98 +/- 0.34, 1.05 +/- 0.20, 0.76 +/- 0.09 and 0.68 +/- 0.19 mumol/day for urinary vitamin B-6; 2.72 +/- 0.94, 3.08 +/- 0.73, 3.80 +/- 0.78 and 4.42 +/- 1.03 mumol/day for fecal vitamin B-6 and 65.0 +/- 23.30, 64.8 +/- 29.80, 49.3 +/- 14.40 and 48.4 +/- 20.20 nM for plasma pyridoxal 5'-phosphate, respectively. 4PA and urinary vitamin B-6 excretion were significantly (P less than or equal to 0.01) higher in the tuna period than in either the whole wheat bread or peanut butter periods.(ABSTRACT TRUNCATED AT 250 WORDS)