Dietary flaxseed lignan extract lowers plasma cholesterol and glucose concentrations in hypercholesterolaemic subjects

Abstract

Lignans, derived from flaxseed, are phyto-oestrogens being increasingly studied for their health benefits. An 8-week, randomised, double-blind, placebo-controlled study was conducted in fifty-five hypercholesterolaemic subjects, using treatments of 0 (placebo), 300 or 600 mg/d of dietary secoisolariciresinol diglucoside (SDG) from flaxseed extract to determine the effect on plasma lipids and fasting glucose levels. Significant treatment effects were achieved (P,0·05 to ,0·001) for the decrease of total cholesterol (TC), LDL-cholesterol (LDL-C) and glucose concentrations, as well as their percentage decrease from baseline. At weeks 6 and 8 in the 600 mg SDG group, the decreases of TC and LDL-C concentrations were in the range from 22·0 to 24·38 % respectively (all P, 0·005 compared with placebo). For the 300 mg SDG group, only significant differences from baseline were observed for decreases of TC and LDL-C. A substantial effect on lowering concentrations of fasting plasma glucose was also noted in the 600 mg SDG group at weeks 6 and 8, especially in the subjects with baseline glucose concentrations $ 5·83 mmol/l (lowered 25·56 and 24·96 %; P¼ 0·015 and P¼ 0·012 compared with placebo, respectively). Plasma concentrations of secoisolariciresinol (SECO), enterodiol (ED) and enterolactone were all significantly raised in the groups supplemented with flaxseed lignan. The observed cholesterol-lowering values were correlated with the concentrations of plasma SECO and ED (r 0·128-0·302; P,0·05 to , 0·001). In conclusion, dietary flaxseed lignan extract decreased plasma cholesterol and glucose concentrations in a dose-dependent manner. Flax is one of the oldest domesticated crops (since 7000 BC) and flour from the seed was used in bread as early as 1000 BC (1) . Today, flaxseed is being increasingly used in the human diet because of its potential health benefits, particularly for cardiovascular protection (2 -4) . Flaxseed is the richest natural source of plant lignans, with secoisolariciresinol diglucoside (SDG) being the principal lignan compound. The concentrations of SDG in flaxseed vary with different cultivars. Eliasson et al. (5) reported that SDG concentrations in twenty-seven flaxseed species ranged from 1·19 to 2·59 % for (þ)-SDG and from 0·22 to 0·5 % (w/w) for its diastereoisomer, (2)-SDG. Westcott et al. (6) presented a range of SDG concentrations from 0·97 to 3·09 % (w/w) in eight varieties of defatted flaxseed meals. Flaxseed lignan along with soyabean isoflavones are phyto-oestrogens commonly consumed in the human diet (7) .To date, a number of clinical trials have been conducted using dietary flaxseed which suggested that SDG lignan may lower plasma cholesterol concentrations. However, the results did not show consistent benefit. In most of these studies, the concentration of lignans was not determined. Differences of study designs, subject characteristics and treatment conditions could confound the outcomes and interpretation of the results (2) . Nevertheless, multiple animal studies do indicate that d...

Impact of flaxseed intake upon metabolic syndrome indicators in female Wistar rats

“…Zhang et al 37 verified the effect of different SDG doses in hypercholesterolemic individuals for eight weeks and they noticed HDL-c decrease. These results showed an increase of 14% in HDL-c concentrations in the supplemented group, but it was not a significant difference.…”

“…This result may indicate that the seed improves insulin sensitivity, thereby increasing glucose uptake. In a recent study, it was found that the flaxseed has hypoglycemic effect on diabetic rats 39 , and SDG present in flaxseed provides better glycemic control in hypercholesterolemic humans 37 . One possible cause for this glycemia reduction is the presence of SDG, which reduces diabetes incidence through its antioxidant activity.…”

Effect of Consumption of Ground Wholeseed Flax on Human Blood Traits

“…Flaxseed contains at least three components that are of health interest: soluble fibers or mucilage (Diederichsen, 2006); high amounts of ALA (Choo, 2007); and the plant lignin secoisolariciresinol diglucoside (Johnsson et al, 2000). In addition, flaxseed also contains small amounts of other lignans, namely pinoresinol, lariciresinol, and matairesinol (Zhang et al, 2008). Even though secoisolariciresinol diglucoside is the predominant lignin in flaxseed, other minor lignans may also contribute to improved health benefits (Adolphe et al, 2010).…”

Optimization of secoisolariciresinol diglucoside extraction from flaxseed (Linum usitatissimumL.) and isolation by a simple HPLC-UV method

“…The enterolignans ED and EL have phytoestrogenic effects due to their similarity to 17β-estradiol, which regulates sex-specific functions, and may be involved in preventing some cancers (Muir & Wescott, 2003). SDG and its metabolites are known for their potential benefits to human health because they act as antioxidants (Hu, Yuan, & Kitts, 2007;Kitts, Yuan, Wijewickreme, & Thompson, 1999), reducing serum cholesterol levels and inhibiting the development of type I and II diabetes (Prasad, 2000;Zhang et al, 2008), and it has been proven that lignans can reduce the incidence of breast cancer and prostate cancer through modulation of the synthesis, bioavailability, and *Corresponding author. Email: ocielmunoz@uach.cl CyTA -Journal of Food, 2015Vol.…”