Dietary intake of vitamin B-6, plasma pyridoxal 5'-phosphate, and homocysteine in Puerto Rican adults

Abstract

Background: Vitamin B-6 is an important cofactor in many metabolic processes. However, vitamin B-6 intake and plasma status have not been well studied in the Puerto Rican population, a group with documented health disparities.

Objective: To assess dietary intake of vitamin B-6, food sources, and plasma status of pyridoxal 5'-phosphate (PLP), and their associations with plasma homocysteine in 1,236 Puerto Rican adults, aged 45 to 75 years, living in the greater Boston area.

Design: Baseline data were analyzed cross-sectionally.

Method: Questionnaire data were collected by home interview. Dietary intake was assessed with a semiquantitative food frequency questionnaire. Plasma PLP and homocysteine were assayed from blood samples collected in the home.

Results: The mean daily intake of vitamin B-6 was 2.90 ± 1.28 mg for men and 2.61 ± 1.29 mg for women (P<0.001). Approximately 11% were deficient (PLP <4.94 ng/mL [PLP <20 nmol/L]) and another 17% insufficient (PLP ≥ 4.94 but <7.41 ng/mL [PLP ≥ 20 but <30 nmol/L]). Household income below the poverty threshold, physical inactivity, and current smoking were significantly associated with lower plasma PLP (P<0.05). Food groups contributing most to vitamin B-6 intake included ready-to-eat cereals, poultry, rice, potatoes, and dried beans. However, only intake of ready-to-eat cereals and use of supplements with vitamin B-6 were significantly associated with plasma PLP sufficiency (≥ 7.41 vs <7.41 ng/mL [PLP ≥ 30 vs <30 nmol/L], P<0.01). Both vitamin B-6 intake and PLP were significantly associated with plasma total homocysteine (P<0.001). The association between PLP and homocysteine remained statistically significant after further adjustment for plasma vitamin B-12 and folate (P=0.028).

Conclusions: Given the known importance of vitamin B-6 to health, the high prevalence of low vitamin B-6 status in this Puerto Rican population is of concern. Further work is needed to clarify the potential role that insufficient vitamin B-6 may have in relation to the observed health disparities in this population.

Copyright © 2010 American Dietetic Association. Published by Elsevier Inc. All rights reserved.

Figures

FIGURE 1

Associations between vitamin B6 intake and plasma pyridoxal-5'-phosphate (PLP) concentration for all (n = 1130, P for trend <0.0001) and for non-supplement using (n = 767, P for trend = 0.002) Puerto Rican adults. Geometric mean (95% confidence interval) of plasma PLP, adjusted for age, sex, energy intake, protein intake, educational attainment (<9th, ≥9th grade education), poverty (yes, no), acculturation score, smoking status (never, former, current), alcohol drinking (not current, current moderate, current heavy), physical inactivity (yes, no), obesity status (normal, overweight, obese), diabetes (yes, no) and plasma creatine, are plotted against median for each quintile group of energy-adjusted vitamin B6 intake.

FIGURE 2

Associations between vitamin B6 status and plasma total homocysteine concentration in Puerto Rican adults. A. Adjusted geometric concentrations of homocysteine (95% confidence interval) are plotted against median of each quintile of energy-adjusted vitamin B6 intake. B. Adjusted geometric homocysteine concentration (95% confidence interval) are plotted against median of each quintile of plasma pyridoxal-5'-phosphate (PLP). In figures A and B for multivariate adjusted results were adjusted for age, sex, energy intake, protein intake, educational attainment (th, ≥9th grade education), poverty (yes, no), acculturation score, smoking status (never, former, current), alcohol use (not current, current moderate, current heavy), physical inactivity (yes, no), obesity status (normal, overweight, obese), diabetes (yes, no), and plasma creatine (n = 1130, P for trend = 0.001 for A and <0.0001 for B). Further adjusted for dietary intake of vitamin B12 and folate for A (n = 1113, P for trend = 0.17), and further adjusted for plasma vitamin B12 and folate for B (n = 1113, P for trend = 0.028).