Relationships between smoking, homocysteine and folate

The present study investigated circulating homocysteine and folate concentrations as well as key dietary variables at baseline and 12 months in smokers and non-smokers enrolled in a randomized dietary intervention trial. The trial investigated the effect of diet modification on breast cancer recurrence. The intervention group was counseled to consume a diet high in fruit, vegetable and fiber and low in fat, while the control group was provided dietary guidelines recommended by the National Cancer Institutes. Participants were 92 smokers matched on baseline dietary folate intake, age and intervention status to 92 non-smokers. Independent t-test analysis was conducted at baseline to compare differences in plasma homocysteine and serum folate concentrations and key dietary variables between smokers and non-smokers. We applied paired t-test analysis to study changes in circulating concentrations of homocysteine and folate and key dietary variables from baseline to 12 months. Multiple linear regression analysis was conducted to study predictors of plasma homocysteine concentrations at baseline. No significant differences were observed for plasma homocysteine and serum folate concentrations at baseline between smokers and non-smokers. However, sub-analysis of participants with ≥10.4 μmol/L showed that smokers had higher circulating homocysteine (P = 0.15) and lower serum folate concentrations (P = 0.59) compared with non-smokers at baseline. In addition, smokers had significantly less healthy diets compared with non-smokers (P < 0.05). Both smokers and non-smokers in the intervention group significantly increased their intakes of vegetable, fruit and fiber and decreased their percent energy from fat from baseline to 12 months (P < 0.05). Plasma homocysteine concentrations were significantly lower and serum folate concentrations were significantly higher for participants who used folate supplements compared with those who did not (P < 0.05). The multivariate analysis showed that serum folate concentration had a significant inverse association with plasma homocysteine concentrations at baseline (P < 0.05). These findings suggest that smokers in a dietary intervention trial can adhere to long-term dietary goals. Circulating homocysteine and folate concentrations are responsive to a diet high in fruits and vegetables and folic acid supplementation. Thus, public health officials should recommend increased folate consumption for the general population.