Nutritional determinants of plasma total homocysteine distribution in the Canary Islands

Objective: We sought to define plasma homocysteine reference values in healthy individuals in the Canary Islands and to determine its relations to folate and vitamin B12 intakes and concentrations. Design: Cross-sectional study. Setting: Population-based representative sample of 557 participants, aged 18-65 years, from the Canary Islands Nutrition Survey (ENCA). Subjects: All participants completed two 24-h dietary recalls and a general questionnaire collecting socio-demographic and health-related lifestyle information. Interventions: Plasma homocysteine and serum vitamin B12 levels were measured by immunoassay, whereas folate levels through an automated ionic capturing method. Results: Median plasma homocysteine was 11.9 mu mol/l, higher in men (13.1 mu mol/l) than in women (10.9 mu mol/l) (P < 0.001) and positively associated with age in both sexes ( P < 0.001). The prevalence of hyperhomocysteinaemia (>= 15 mu mol/l), 21.4%, was also greater in men (32.2%) than in women (13.4%). There were significant negative correlations between plasma homocysteine and serum (r = -0.32, P < 0.001) and erythrocyte (r = -0.26, P < 0.001) folate, as well as serum vitamin B12 (r = -0.28, P < 0.001) concentrations. When divided in quartiles of vitamin intakes or concentrations, men with the lowest vitamin B12 and folate serum values had significantly higher plasma homocysteine concentrations than those in the other three quartiles. In women, hyperhomocysteinaemia was higher in the lowest quartiles of folate intake and serum and erythrocyte folate concentrations. Conclusions: These data provide further evidence that hyperhomocysteinaemia is a sensitive marker of inadequate folate and vitamin B12 status, allowing for the identification of those with greatest need for nutritional interventions.