Assessment of vitamin B-6 status in young women consuming a controlled diet containing four levels of vitamin B-6 provides an estimated average requirement and recommended dietary allowance

J Nutr. 2001 Jun;131(6):1777-86. doi: 10.1093/jn/131.6.1777.


The Recommended Dietary Allowance (RDA) of vitamin B-6 for young women was recently reduced from 1.6 to 1.3 mg/d based on an adequate plasma pyridoxal phosphate (PLP) concentration of 20 nmol/L. To assess vitamin B-6 requirements and suggest recommendations for intake, seven healthy young women consumed a controlled diet providing 1.2 g protein/kg body weight for a 7-d adjustment period (1.0 mg vitamin B-6/d) and three successive 14-d experimental periods (1.5, 2.1 and 2.7 mg/d, respectively). Direct and indirect vitamin B-6 status indicators were measured in plasma, erythrocytes and urine. Indicators most strongly correlated with vitamin B-6 intake [i.e., plasma and erythrocyte PLP, urinary 4-pyridoxic acid (4-PA) and total vitamin B-6] were regressed on vitamin B-6 intake and the dietary vitamin B-6 to protein ratio. Inverse prediction using adequate and baseline values estimated vitamin B-6 requirement. Adequate values were determined for plasma PLP and urinary 4-PA from baseline values of 60 previous subjects, using the statistical method suggested by Sauberlich. The current study suggests a vitamin B-6 Estimated Average Requirement (EAR) for young women of 1.1 mg/d or 0.016 mg/g protein, and a RDA of 1.5 mg/d or 0.020 mg/g protein. When results from this study are combined with data from four other recent studies, the combined data predict an EAR of 1.2 mg/d or 0.015 mg/g protein, and a RDA of 1.7 mg/d or 0.018 mg/g protein. This study suggests that the current vitamin B-6 RDA may not be adequate.

Publication types

  • Clinical Trial
  • Comparative Study
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Administration, Oral
  • Adult
  • Alanine Transaminase / analysis
  • Aspartate Aminotransferases / analysis
  • Body Mass Index
  • Diet / standards*
  • Erythrocytes / metabolism
  • Ethnic Groups
  • Female
  • Humans
  • Nutrition Policy
  • Nutritional Status*
  • Pyridoxal Phosphate / blood
  • Pyridoxal Phosphate / urine
  • Pyridoxamine / analogs & derivatives
  • Pyridoxamine / blood
  • Pyridoxamine / urine
  • Pyridoxic Acid / blood
  • Pyridoxic Acid / urine
  • Pyridoxine / administration & dosage*
  • Pyridoxine / blood
  • Pyridoxine / urine


  • Pyridoxic Acid
  • Pyridoxal Phosphate
  • Pyridoxamine
  • Aspartate Aminotransferases
  • Alanine Transaminase
  • Pyridoxine
  • pyridoxamine phosphate