Responsiveness of homocysteine concentrations to food and supplemental folate intakes in smokers and never-smokers enrolled in a diet intervention trial.

We investigated circulating homocysteine concentrations in relation to smoking, folate intake (from food and supplements), serum folate concentrations, and other dietary variables. The present study is part of a parent trial assessing the effects of increasing vegetable, fruit, and fiber intakes and reducing the percentage of energy obtained from fat on breast cancer recurrence in 3,088 women previously diagnosed with breast cancer. Of the 121 smokers enrolled in the parent trial, 85 were available at baseline for the present study and were randomly matched to 85 never-smokers on baseline folate intake, age, and intervention status. Follow-up data were available on 53 smokers (22 intervention and 31 comparison) and 56 never-smokers (24 intervention and 32 comparison). No significant differences in circulating homocysteine and folate concentrations were observed between smokers and never-smokers at baseline. For smokers, significant decreases in circulating homocysteine and significant increases in folate concentrations (p < .05) from baseline to 12 months were observed in the comparison group. For never-smokers, significant decreases in circulating homocysteine and significant increases in folate concentrations were observed in the intervention and comparison groups (p < .05). In the multivariate analysis, changes in serum folate concentration and supplemental folic acid were significantly associated with change in plasma homocysteine concentrations (p < .05). These findings show that increasing supplemental folic acid can reduce homocysteine concentrations, which may have implications for lowering cardiovascular disease risk for smokers and never-smokers.