Plasma pyridoxal 5'-phosphate in the US population: the National Health and Nutrition Examination Survey, 2003-2004

BACKGROUND No large-scale, population-based study has considered the descriptive epidemiology of vitamin B-6 status with use of plasma pyridoxal 5'-phosphate (PLP), the indicator of vitamin B-6 adequacy used to set the current Recommended Dietary Allowance, which is < or = 2 mg/d for all subgroups.
OBJECTIVES We sought to examine the epidemiology of vitamin B-6 status in the US population.
METHODS In > 6000 participants aged > or = 1 y in the National Health and Nutrition Examination Survey (2003-2004), we considered relations between plasma {PLP} and various subject characteristics and examined trends in plasma {PLP} and homocysteine with vitamin B-6 intake, both overall and in selectedsubgroups.
RESULTS In males, plasma {PLP} decreased with age after adolescence only in nonusers of supplemental vitamin B-6. Regardless of supplement use, plasma {PLP} concentrations of women of childbearing age were significantly lower than those of comparably aged men, and most oral contraceptive users had plasma {PLP} < 20 {nmol/L.} The prevalence of low plasma {PLP} was significantly > 3% at vitamin B-6 intakes from 2 to 2.9 mg/d in all subgroups and at intakes from 3 to 4.9 mg/d in smokers, the elderly, {non-Hispanic} blacks, and current and former oral contraceptive users. Intakes from 3 to 4.9 mg/d compared with < 2 mg/d were associated with significant protection from low plasma {PLP} in most subgroups and from hyperhomocysteinemia in the elderly.
CONCLUSIONS Vitamin B-6 intakes of 3 to 4.9 mg/d appear consistent with the definition of a Recommended Dietary Allowance for most Americans. However, at that intake level, substantial proportions of some population subgroups may not meet accepted criteria for adequate vitamin B-6 status.