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

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.