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

Am J Clin Nutr. 2008 May;87(5):1446-54. doi: 10.1093/ajcn/87.5.1446.


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 selected subgroups.

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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Adolescent
  • Adult
  • Age Factors
  • Aged
  • Aged, 80 and over
  • Biomarkers / blood
  • Child
  • Child, Preschool
  • Diet*
  • Dietary Supplements*
  • Female
  • Homocysteine / blood
  • Humans
  • Infant
  • Male
  • Middle Aged
  • Nutrition Policy
  • Nutrition Surveys
  • Nutritional Requirements
  • Nutritional Status*
  • Pyridoxal Phosphate / blood*
  • Sex Factors
  • United States
  • Vitamin B 6 / administration & dosage*
  • Vitamin B 6 / blood*
  • Vitamin B 6 Deficiency / blood
  • Vitamin B 6 Deficiency / epidemiology


  • Biomarkers
  • Homocysteine
  • Pyridoxal Phosphate
  • Vitamin B 6