(25-08-09) Meta-analysis of the effects of flaxseed interventions on blood lipids1,2,3,4

An Pan, Danxia Yu, Wendy Demark-Wahnefried, Oscar H Franco and Xu Lin

1 From the Key Laboratory of Nutrition and Metabolism, Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences and Graduate School of the Chinese Academy of Sciences, Shanghai, China (AP, DY, and XL); the Division of Cancer Prevention and Population Sciences, MD Anderson Cancer Center, University of Texas, Houston, TX (WD-W); the University of Warwick, Warwick Medical School, Health Sciences Research Institute, Coventry, United Kingdom (OHF); and Unilever R&D, Colworth Science Park, Sharnbrook, MK, United Kingdom (OHF).
2 AP and DY contributed equally to this work.
3 This study was funded by the Chinese Academy of Sciences (The Knowledge Innovation Program, Grants KSCX1-YW-02 and KSCX1-YW-R-116; the Chief Scientist Program of Shanghai Institutes for Biological Sciences to XL, grant SIBS2008006), the Ministry of Science and Technology of China (grant 2008DFA31960).
4 Address correspondence to X Lin, Institute for Nutritional Sciences, Chinese Academy of Sciences, 294 Tai-Yuan Road, Shanghai, 200031, China. E-mail: [email protected] .
Background: Several clinical trials have investigated the effects of flaxseed and flaxseed-derived products (flaxseed oil or lignans) on blood lipids; however, the findings have been inconsistent.
Objective: We aimed to identify and quantify the effectiveness of flaxseed and its derivatives on blood lipid profiles.
Design: A comprehensive literature search was performed on the basis of English reports of randomized controlled trials of flaxseed or its derivatives on lipid profiles in adults, which were published from January 1990 to October 2008. Attempts also were made to access unpublished data. Study quality was assessed by using the Jadad score, and a meta-analysis was conducted.
Results: Twenty-eight studies were included. Flaxseed interventions reduced total and LDL cholesterol by 0.10 mmol/L (95% CI: ?0.20, 0.00 mmol/L) and 0.08 mmol/L (95% CI: ?0.16, 0.00 mmol/L), respectively; significant reductions were observed with whole flaxseed (?0.21 and ?0.16 mmol/L, respectively) and lignan (?0.28 and ?0.16 mmol/L, respectively) supplements but not with flaxseed oil. The cholesterol-lowering effects were more apparent in females (particularly postmenopausal women), individuals with high initial cholesterol concentrations, and studies with higher Jadad scores. No significant changes were found in the concentrations of HDL cholesterol and triglycerides.
Conclusions: Flaxseed significantly reduced circulating total and LDL-cholesterol concentrations, but the changes were dependent on the type of intervention, sex, and initial lipid profiles of the subjects. Further studies are needed to determine the efficiency of flaxseed on lipid profiles in men and premenopausal women and to explore its potential benefits on other cardiometabolic risk factors and prevention of cardiovascular disease.

Source: American Journal of Clinical Nutrition, doi:10.3945/ajcn.2009.27469
Vol. 90, No. 2, 288-297, August 2009

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