Abstract
BackgroundFlaxseed consumption has been shown to improve blood lipids in humans and flaxseed-derived lignan has been shown to enhance glycemic control in animals. The study aimed to investigate the effect of a flaxseed-derived lignan supplement on glycemic control, lipid profiles and insulin sensitivity in type 2 diabetic patients.Methodology/Principal FindingsThis was a randomized, double-blind, placebo-controlled, cross-over trial and it was conducted between April and December 2006 in Shanghai, China. Seventy-three type 2 diabetic patients with mild hypercholesterolemia were enrolled into the study. Patients were randomized to supplementation with flaxseed-derived lignan capsules (360 mg lignan per day) or placebo for 12 weeks, separated by an 8-week wash-out period. HbA1c, lipid profiles, insulin resistance index and inflammatory factors were measured. Sixty-eight completed the study and were included in the analyses. The lignan supplement significantly improved glycemic control as measured by HbA1c (-0.10±0.65 % vs. 0.09±0.52 %, P = 0.001) compared to placebo; however, no significant changes were observed in fasting glucose and insulin concentrations, insulin resistance and blood lipid profiles. Urinary excretion of lignan metabolites (enterodiol and enterolactone) was significantly higher after the lignan supplement intervention compared to baseline (14.2±18.1 vs. 1.2±2.4 µg/mL, P<0.001). Data also suggested minimal competition between lignan and isoflavones for bioavailability when measured by the excretion concentrations.Conclusions/SignificanceDaily lignan supplementation resulted in modest, yet statistically significant improvements in glycemic control in type 2 diabetic patients without apparently affecting fasting glucose, lipid profiles and insulin sensitivity. Further studies are needed to validate these findings and explore the efficacy of lignans on type 2 diabetes.Trial RegistrationClinicalTrials.gov NCT00363233
Highlights
Type 2 diabetes is a serious and economically devastating disease
To the best of our knowledge, the present study is the first to investigate the effect of flaxseed-derived lignan on glycemic control, lipid profiles and inflammatory status in type 2 diabetes
We showed that 12-week supplementation of a flaxseed-derived lignan complex, which provided 360 mg/day secoisolariciresinol diglucoside (SDG), statistically significantly reduced HbA1c concentrations in type 2 diabetic patients as compared with the placebo
Summary
Type 2 diabetes is a serious and economically devastating disease. Over the past few decades its worldwide prevalence has increased dramatically, especially in the developing countries such as China and India [1]. Null findings were observed in a recent study of a flaxseed-derived lignan supplement (500 mg/day) on lipid profiles in 22 healthy women [14]. The study aimed to investigate the effect of a flaxseed-derived lignan supplement on glycemic control, lipid profiles and insulin sensitivity in type 2 diabetic patients. The lignan supplement significantly improved glycemic control as measured by HbA1c (-0.1060.65 % vs 0.0960.52 %, P = 0.001) compared to placebo; no significant changes were observed in fasting glucose and insulin concentrations, insulin resistance and blood lipid profiles. Lignan supplementation resulted in modest, yet statistically significant improvements in glycemic control in type 2 diabetic patients without apparently affecting fasting glucose, lipid profiles and insulin sensitivity.
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