Vitamin B-6 requirement and status assessment: young women fed a depletion diet followed by a plant- or animal-protein diet with graded amounts of vitamin B-6

Am J Clin Nutr. 1995 May;61(5):1091-101. doi: 10.1093/ajcn/61.4.1091.


The vitamin B-6 requirement of young women consuming a high-protein diet (1.55 g/kg body wt) and the effect of protein quality on this requirement was studied. In addition, the response of clinical, functional, and biochemical measures of vitamin B-6 nutriture to short-term depletion and step-wise repletion of vitamin B-6 were evaluated. Eight healthy young women resided in a metabolic unit and were fed a formula depletion diet (< 0.05 mg vitamin B-6/d) for 11-28 d followed by either an animal-protein (AP) or plant-protein (PP) diet with successively increasing vitamin B-6 intakes (0.5, 1.0, 1.5, and 2.0 mg/d) for periods of 14-21 d. Animal proteins were primarily from dairy and poultry sources and plant proteins were primarily from legumes. Vitamin B-6 status measures were assessed at weekly intervals. Results showed that a PP diet does not elevate the vitamin B-6 requirement over that required for an AP diet given the high amount of dietary protein used in this study. It was also found that 0.015 mg vitamin B-6/g protein intake normalized most biochemical indexes of vitamin B-6 status (including those indicative of functional status), and that 0.020 mg/g protein normalized all biochemical measures except total urinary vitamin B-6. Adding a margin of safety to either the 0.015 or 0.020 mg/g protein intake would raise the vitamin B-6 requirement for young women above the currently recommended dietary allowance of 0.016 mg/g protein.

Publication types

  • Clinical Trial
  • Comparative Study
  • Randomized Controlled Trial

MeSH terms

  • Adult
  • Analysis of Variance
  • Biomarkers
  • Dairy Products
  • Dietary Proteins / analysis
  • Dietary Proteins / pharmacology*
  • Dietary Proteins / standards
  • Dose-Response Relationship, Drug
  • Female
  • Food, Formulated* / standards
  • Humans
  • Nutrition Assessment
  • Nutritional Requirements
  • Plant Proteins / analysis
  • Plant Proteins / pharmacology*
  • Plant Proteins / standards
  • Pyridoxal Phosphate / blood
  • Pyridoxic Acid / urine
  • Pyridoxine / administration & dosage
  • Pyridoxine / analysis
  • Pyridoxine / pharmacology*
  • Xanthurenates / urine


  • Biomarkers
  • Dietary Proteins
  • Plant Proteins
  • Xanthurenates
  • xanthurenic acid
  • Pyridoxic Acid
  • Pyridoxal Phosphate
  • Pyridoxine