Vitamin B-6 requirement and status assessment of young women fed a high-protein diet with various levels of vitamin B-6

Abstract

The vitamin B-6 requirement of young women consuming a constant high-protein diet (1.55 g/kg body wt) and the effect of various ratios of vitamin B-6 to protein on this requirement were studied. Eight women were fed a lactoovovegetarian basal diet containing 0.45 mg vitamin B-6 (2.66 micromol as pyridoxine) and 30 micromol carnitine for 92 d. The protocol consisted of successive baseline adjustment (9 d), depletion (27 d), and repletion (two 21-d and then one 14-d) periods. Vitamin B-6 intakes were 1.60, 0.45, 1.26, 1.66, and 2.06 mg, resulting in ratios of vitamin B-6 (in mg) to protein (in g) for the five periods of 0.016, 0.005, 0.013, 0.017, and 0.021, respectively. Direct and indirect as well as short- and long-term vitamin B-6 status measures were assessed weekly. Regression analysis revealed that the amount of dietary vitamin B-6 required to normalize urinary 4-pyridoxic acid, plasma pyridoxal-P, erythrocyte pyridoxal-P and pyridoxal, and erythrocyte alanine and aspartate aminotransferase activity coefficients to predepletion baseline values was 1.94 mg vitamin B-6/d (0.019 mg vitamin B-6/g protein). This study suggests that the current vitamin B-6 recommended dietary allowance of 1.6 mg/d based on 0.016 mg/g protein is not an adequate intake and may require reevaluation.

Vitamin B6 intakes and status of mechanically ventilated critically ill patients in Taiwan

“…Patients had low hemoglobin concentrations in our study; however, vitamin B6 status revealed no effect on hemoglobin concentration. This finding agrees with that of other studies (Ribaya-Mercado et al, 1991;Huang et al, 1998). Patients had low hemoglobin concentrations which may be caused by other factors.…”

“…Our critically ill patients not only had an adequate mean 4-PA concentration ( > 3.0 mmol=day; Leklem, 1990), but it also increased proportionately to vitamin B6 intake. In agreement with previous reports (Brown et al, 1975;Leklem, 1990;Huang et al, 1998), urinary 4-PA excretion changed rapidly in response to a change in vitamin B6 intake.…”

Literature search and review related to specific preparatory work in the establishment of Dietary Reference Values for Niacin, Biotin and Vitamin B6

“…In this review, three of the four papers on intake-status relationship did indeed use more than three indicators to assess vitamin B6 status (Hansen et al 2001, Huang et al 1998, Kretsch et al 1995. In addition, most papers on the association between status indicators of vitamin B6 and certain health outcomes used plasma PLP, which is generally accepted as the best indicator for vitamin B6 status.…”

“…The depletion-repletion study of Huang et al aimed to examine the vitamin B6 requirement of young women (age range 28-34 years), consuming a constant high-protein diet (1.55 g/kg body weight/day), and the effect of various vitamin B6 intakes on this requirement (Huang et al 1998). This study was at high risk of bias.…”

“…Indicators most strongly related to vitamin B6 intake were plasma and erythrocyte PLP, urinary pyridoxic acid (4-PA), and urinary total vitamin B6. When Hansen et al combined their results with the results of previous studies in a linear regression analysis, such as the studies of Huang et al (Huang et al 1998) and Kretsch et al (Kretsch et al 1995), an RDA of 1.5-1.7 mg/d (0.018-0.020 mg/g protein) for young women was calculated.…”