Association between dietary antioxidant vitamins intake and homocysteine levels in middle-aged and older adults with hypertension: a cross-sectional study

OBJECTIVES: Plasma total homocysteine (tHcy) has been implicated in the development of cardiovascular disease. This study aimed to assess the relationship of dietary antioxidant vitamins intake with tHcy levels in middle-aged and older adults with hypertension. DESIGN: A cross-sectional study. SETTING: The survey was conducted in the Nanshan district of Shenzhen. PARTICIPANTS: A total of 1465 middle-aged and older adults with hypertension were included between July and September of 2013. MEASUREMENTS: Hyperhomocysteinaemia (HHcy) was defined as tHcy ≥15 µmol/L. Some dietary antioxidant vitamins (vitamin C (VC) and vitamin E (VE), carotenes, retinol, lutein) intake was estimated using the Food Frequency Questionnaire. Sociodemographic and potential covariates were evaluated through questionnaires, anthropometric measurements and blood tests. The association between dietary intakes of antioxidant vitamins and tHcy concentration were evaluated by multiple linear regression analyses after napierian logarithm transformed. Multiple logistic regression models were further used to determine ORs and 95% CIs. RESULTS: The β (95% CIs) of VC intake and tHcy was −0.050 (−0.084 to –0.016). Compared with the lowest quartile in the fully adjusted model, the ORs (95% CIs) for HHcy levels across quartiles of dietary VC intake were 0.82 (0.57 to 1.16), 0.49 (0.33 to 0.74) and 0.40 (0.22 to 0.74) (p for trend=0.001). The β (95% CIs) of retinol intake and tHcy was −0.021 (−0.041 to –0.002) and the ORs (95% CIs) in the third quartile of retinol intake was 0.61 (0.42 to 0.86), while the effect for the highest quartile was not significant (p for trend=0.951). No significant association was observed between dietary VE, carotenes and lutein intake and HHcy. CONCLUSIONS: A linear inverse association between dietary VC intake and HHcy prevalence, and an L-shaped association between dietary retinol intake and HHcy prevalence were found in Chinese middle-aged and older adults with hypertension.