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.
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.
Hansen
C M
CM
Department of Food Science and Human Nutrition, Washington State University, Pullman, WA 99164-6376, USA.
Shultz
T D
TD
Kwak
H K
HK
Memon
H S
HS
Leklem
J E
JE
D000284:Administration, Oral; D000328:Adult; D000410:Alanine Transaminase / Q000032:analysis; D001219:Aspartate Aminotransferases / Q000032:analysis; D015992:Body Mass Index; D004032:Diet / Q000592:standards*; D004912:Erythrocytes / Q000378:metabolism; D005006:Ethnicity; D005260:Female; D006801:Humans; D018673:Nutrition Policy; D009752:Nutritional Status; D011732:Pyridoxal Phosphate / Q000097:blood / Q000652:urine; D011733:Pyridoxamine / Q000031:analogs & derivatives / Q000097:blood / Q000652:urine; D011735:Pyridoxic Acid / Q000097:blood / Q000652:urine; D011736:Pyridoxine / Q000008:administration & dosage* / Q000097:blood / Q000652:urine
D011735:Pyridoxic Acid; D011732:Pyridoxal Phosphate; D011733:Pyridoxamine; D001219:Aspartate Aminotransferases; D000410:Alanine Transaminase; D011736:Pyridoxine; C010627:pyridoxamine phosphate