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 [2 mg or less] for all subgroups.
Objectives: We sought to examine the epidemiology of vitamin B-6 status in the US population.
Methods: In more than 6000 participants aged 1 year or more 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 selected subgroups.
In males, plasma PLP decreased with age after adolescence only in nonusers of supplemental vitamin B-6.
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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 > [more than] 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. [Hyperhomocysteinemia is increased homocysteine, associated with impaired B vitamin intake/absorption and elevated cardiovascular risk.]
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.
Source: American Journal of Clinical Nutrition, May 2008. 87(5):1446-54. PMID: 18469270, by Morris MS, Picciano MF, Jacques PF, Selhub J. Jean Mayer US Department of Agriculture Human Nutrition Research Center on Aging at Tufts University, Boston, Massachusetts, USA. [ E-mail: email@example.com]