B Vitamins and Plasma Homocysteine Concentrations in an Urban and Rural Area of Costa Rica

Abstract

Objective: We studied the association between total plasma homocysteine (tHcy) concentrations and folate, B12, and B6 status in the urban and rural areas of Costa Rica.Subjects and Methods: We determined plasma tHcy concentrations and assessed dietary folate, B12 and B6 intake by a food frequency questionnaire in 462 subjects selected by stratified random sampling in the urban and rural areas of Puriscal, Costa Rica. Plasma folate and vitamin B12 concentrations were measured in women.Results: THcy concentrations were higher (p < 0.01) in the rural compared with the urban area: 12.0 μmol/L vs. 8.9 μmol/L in men, and women 7.3 μmol/L vs. 5.5 μmol/L in women, respectively. The prevalence of hyperhomocysteinemia (greater than 15.0 μmol/L) was twice as high in rural compared with urban men (19.8% vs. 10.8%, p = 0.06) and women (6.6% vs. 3.4%, p = 0.26). Most study subjects (98%) had folate intakes that were less than the recommended 400 μg/day. In women, 31% of those living in the urban area and 40% of those in the rural area had plasma folate concentrations of less than 6.8 nmol/L, an indicator of folate deficiency. In women, age-adjusted mean tHcy concentrations (μmol/L) were higher in the lowest compared with highest quintiles for dietary vitamin B6 (9.9 vs. 5.4, p < 0.05), B12 (9.2 vs. 4.9, p < 0.01), and folate (7.0 vs. 5.7, p = 0.87). Similar results were found for plasma B12 (9.9 vs. 5.4, p < 0.01) and folate (10.5 vs. 5.0, p < 0.0001).Conclusions: Residents of the rural area in Puriscal, Costa Rica have higher plasma concentrations of tHcy and lower intake of B vitamins, particularly in women. Because these characteristics are associated with high risk of cardiovascular disease, the efficacy of food fortification program in rural areas should be carefully addressed.