B vitamins and plasma homocysteine concentrations in an urban and rural area of Costa Rica

Objective: We studied the association between total plasma homocysteine (tHcy) concentrations and folate, B-12, and B-6 status in the urban and rural areas of Costa Rica. Subjects and Methods: We determined plasma tHcy concentrations and assessed dietary folate, B-12 and B-6 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 B-12 concentrations were measured in women. Results: THcy concentrations were higher (p < 0.01) in the rural compared with the urban area: 12.0 mumol/L vs. 8.9 mumol/L in men, and women 7.3 mumol/L vs. 5.5 mumol/L in women, respectively. The prevalence of hyperhomocystememia (greater than 15.0 mumol/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 mug/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 (mumol/L) were higher in the lowest compared with highest quintiles for dietary vitamin B-6 (9.9 vs. 5.4, p < 0.05), B-12 (9.2 vs. 4.9, p < 0.01), and folate (7.0 vs. 5.7, p = 0.87). Similar results were found for plasma B-12 (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.