Flaxseed oil intake reduces serum small dense low-density lipoprotein concentrations in Japanese men: a randomized, double blind, crossover study

BACKGROUND: The effects of alpha-linolenic acid (ALA) on cardiovascular risk factors considerably vary between published reports. Therefore, we investigated the effects of 12-week supplementation with flaxseed oil (FO), which is a rich source of ALA, on cardiovascular risk factors such as serum small dense low-density lipoprotein (sd-LDL) concentrations. METHODS: In a randomized, double blind, crossover study, 15 subjects ingested 10 g of FO or corn oil (CO), containing 5.49 g and 0.09 g of ALA, respectively, once daily with dinner. Blood samples were collected at 0, 4 and 12 weeks, and were used for analysis of serum lipid, lipid-related proteins, serum fatty acids and serum sd-LDL cholesterol. Differences during the test period were identified using a repeated-measures analysis of variance (ANOVA) for within-group effects. Group differences were identified using paired t-test at each blood sampling time point. RESULTS: ALA and eicosapentaenoic acid concentrations were significantly higher in the FO period at 4 and 12 weeks than in the CO period. No significant differences in docosahexaenoic acid concentrations were observed between two periods, and cholesteryl ester transfer protein and apolipoprotein B concentrations were significantly lower in the FO period than in the CO period at 12 weeks. FO supplementation was associated with a significant decrease in sd-LDL concentrations at 4 and 12 weeks, and CO supplementation had no effect. Moreover, sd-LDL concentrations were significantly lower in the FO period than in the CO period at 4 weeks. Among subjects with triglyceride (TG) concentrations of >100 mg/dl, FO supplementation markedly reduced sd-LDL concentrations at 4 and 12 weeks compared with baseline. Sd-LDL concentrations significantly differed between the periods at both 4 and 12 weeks. CONCLUSION: This study indicates that the FO, which is a rich source of ALA, leads to lower sd-LDL cholesterol concentrations.