A lignan complex isolated from flaxseed does not affect plasma lipid concentrations or antioxidant capacity in healthy postmenopausal women

The effects of flaxseed (Linum usitatissimum) supplementation on anthropometric indices: An updated systematic review and meta-analysis of randomized clinical trials

OBJECTIVE

Flaxseed (Linum usitatissimum) supplementation has shown promise as an anti-obesity agent in various clinical trials, although results have been inconsistent. To provide a more accurate assessment of the impact of flaxseed supplementation on anthropometric indices, a systematic review and meta-analysis was performed.

METHODS

We searched several international databases until August 2023, including Scopus, PubMed, Web of Science, Embase, and Cochrane Library. Weighted mean differences (WMDs) were analyzed using a random-effects model.

RESULTS

Sixty-four trials comprising 72 treatment arms were included. All studies reported the intervention types (Lignans, Whole flaxseed, and Flaxseed oil) and dosage. However, three studies did testing for purity, and 40 studies reported potency. Also, the risk of contamination with heavy metals was not mentioned in studies. Another limitation was the lack of blind evaluation in the studies. According to three trials included in the systematic review, flaxseed did not affect anthropometric indices. Our meta-analysis revealed significant reductions in body weight (WMD = -0.63 kg; 95 % CI: -1.00, -0.27, P < 0.001; I2 = 76.7 %, P < 0.001), body mass index (BMI) (WMD: -0.24 kg/m2, 95 % CI: -0.36, -0.11, P < 0.001; I2 = 78.5 %, P < 0.001) and waist circumference (WC) (WMD: -1.43 cm, 95 % CI: -2.06, -0.80, P < 0.001; I2 = 81.1 %, P < 0.001) following flaxseed supplementation. Subgroup analyses indicated that interventions lasting 10-20 weeks, and studies involving subjects with higher BMI (>30 kg/m2) showed more significant anti-obesity effects. Based on the GRADE evaluation, body weight, BMI, and WC results were considered as moderate-certainty evidence.

CONCLUSION

Our systematic review and meta-analysis suggests that supplementation with flaxseed (Linum usitatissimum) leads to meaningful improvements in body weight, BMI, and WC. Therefore, flaxseed can be considered as an adjunctive therapeutic approach in improving obesity.

Enterolignans: from natural origins to cardiometabolic significance, including chemistry, dietary sources, bioavailability, and activity

The enterolignans, enterolactone and enterodiol, the main metabolites produced from plant lignans by the gut microbiota, have enhanced bioavailability and activity compared to their precursors, with beneficial effects on metabolic and cardiovascular health. Although extensively studied, the biosynthesis, cardiometabolic effects, and other therapeutic implications of mammalian lignans are still incompletely understood. The aim of this review is to provide a comprehensive overview of these phytoestrogen metabolites based on up-to-date information reported in studies from a wide range of disciplines. Established and novel synthetic strategies are described, as are the various lignan precursors, their dietary sources, and a proposed metabolic pathway for their conversion to enterolignans. The methodologies used for enterolignan analysis and the available data on pharmacokinetics and bioavailability are summarized and their cardiometabolic bioactivity is explored in detail. The special focus given to research on the health benefits of microbial-derived lignan metabolites underscores the critical role of lignan-rich diets in promoting cardiovascular health.

Availability of dietary secoisolariciresinol diglucoside on borderline blood cholesterol level in men: a randomized, parallel, controlled, double-blinded clinical trial

Borderline low-density lipoprotein cholesterol levels (120-139 mg/dl) increase the risk of cardiovascular disease. Therefore, the use of functional dietary nutrients is expected to control blood low-density lipoprotein cholesterol levels. This study aimed to evaluate the effect of dietary secoisolariciresinol diglucoside on blood cholesterol in healthy adults with borderline low-density lipoprotein cholesterol levels. A randomized, parallel, controlled, double-blinded clinical trial was performed for participants with borderline low-density lipoprotein cholesterol levels, for 12 weeks with secoisolariciresinol diglucoside (60 mg/day) or placebo. Lipid profile [low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol/high-density lipoprotein cholesterol ratio, total cholesterol, and triglycerides] and liver disease risk markers were measured at weeks 0, 4, 8, and 12. Analyzing 36 participants in each group revealed a significant interaction between treatment and time, indicating reduced low-density lipoprotein cholesterol (p = 0.049) and total cholesterol (p = 0.020) levels in secoisolariciresinol diglucoside-receiving men but not women. However, no significant differences were observed in other markers regardless of gender. The results suggest that a daily intake of 60 mg of secoisolariciresinol diglucoside lowers low-density lipoprotein cholesterol and total cholesterol levels in men with borderline low-density lipoprotein cholesterol, proposing secoisolariciresinol diglucoside potential as a functional dietary nutrient for cardiovascular disease prevention. This study was registered in the UMIN-CTR database (UMIN000046202).

The impact of consuming technologically processed functional foods enriched/fortified with (poly)phenols on cardiometabolic risk factors: a systematic review of randomized controlled trials

Cardiovascular diseases are a major global cause of death and healthcare costs, emphasizing the need for effective prevention and management of cardiometabolic risk factors. One promising approach is the consumption of technologically processed functional foods enriched/fortified with (poly)phenols. The current systematic review aimed to evaluate the human clinical trials evidence on the effect of intake of these foods on reducing the most common cardiometabolic risk factors. 12 randomized controlled studies were included in the systematic review, with varying food intake amounts (27-360 g/day) and (poly)phenol doses (32.5-850 mg/day). These interventions included consumption of functional bakery goods, cereal bars, pasta, chocolate, and yogurt, with supplementation periods spanning from 2 to 52 wk. Several foods, such as green tea extract-fortified rye bread and olive fruit (poly)phenol-fortified yogurt, significantly lowered blood pressure. Flavonoid-enriched chocolate, hydroxytyrosol-fortified bread, and other products influenced glucose metabolism. Additionally, various functional foods were associated with improved blood lipid levels. While these results indicate the health advantages of consuming technologically processed functional foods enriched/fortified with (poly)phenols, caution is warranted due to the scarcity and limitations of existing studies. Further research is needed to confirm and expand upon these results in the prevention and management of cardiometabolic risk factors.

Polyphenols and atherosclerosis: A critical review of clinical effects on LDL oxidation

Atherosclerosis is a major etiology of cardiovascular disease that causes considerable mortality. Oxidized low-density lipoprotein (oxLDL) is a fundamental attributor to atherosclerosis. Therefore, there seems to be an essential place for antioxidant therapy besides the current treatment protocols for coronary heart disease. Polyphenols are a class of compounds with substantial antioxidant properties that have shown the ability to reduce LDL oxidation in preclinical studies. However, clinical evidence has not been as conclusive although offering many promising signs. This review aims to examine the trials that have evaluated how dietary intake of polyphenols in different forms might influence the oxidation of LDL. Lowering the circulating cholesterol, incorporation into LDL particles, and enhancing systemic antioxidant activity are among the main mechanisms of action for polyphenols for lowering oxLDL. On the other hand, the population under study significantly affects the impact on oxLDL, as the type of the supplement and phenolic content. To conclude, although the polyphenols might decrease inflammation and enhance endothelial function via lowering oxLDL, there are still many gaps in our knowledge that need to be filled with further high-quality studies.

Role of Phytoestrogen-Rich Bioactive Substances (Linum usitatissimum L., Glycine max L., Trifolium pratense L.) in Cardiovascular Disease Prevention in Postmenopausal Women: A Systematic Review and Meta-Analysis

The aim of this report was to determine the impact of flaxseed, soy and red clover, and their bioactive substances on the lipid profile in postmenopausal women in cardiovascular diseases prevention. We used the following databases: MEDLINE (PubMed), EMBASE and the Cochrane Library. Meta-analysis indicates that the intake of flaxseed by postmenopausal women is associated with a statistically significant reduction in total cholesterol (TC) levels (weighted-mean difference (WMD) = -0.26; 95% confidence interval (95% CI): -0.38 to -0.13; p = 0.0001), low-density lipoprotein cholesterol (LDL-C) levels (WMD = -0.19; 95% CI: -0.30 to -0.08; p = 0.0006), and high-density lipoprotein cholesterol (HDL-C) levels (WMD = -0.06; 95% CI: -0.11 to -0.01; p = 0.0150). The effect of soy protein on the lipid profile showed a significant decrease in TC levels: WMD = -0.15; 95% CI: -0.25-0.05; p = 0.0048, LDL-C levels: WMD = -0.15; 95% CI: -0.25-0.05; p = 0.0067, as well as a significant increase in HDL-C levels: WMD = 0.05; 95% CI: 0.02-0.08; p = 0.0034. Changes in the lipid profile showed a significant reduction in TC levels after the use of red clover (WMD = -0.11; 95% CI: -0.18--0.04; p = 0.0017) and a significant increase in HDL-C levels (WMD = 0.04; 95% CI: 0.01 to 0.07; p = 0.0165). This meta-analysis provides evidence that consuming flaxseed, soy and red clover can have a beneficial effect on lipids in postmenopausal women and suggest a favorable effect in preventing cardiovascular diseases.

Availability of bioactive flax lignan from foods and supplements

Hyperlipidemia, high levels of blood lipids including cholesterol and triglycerides, is a major risk factor for cardiovascular disease. Traditional treatments of hyperlipidemia often include lifestyle changes and pharmacotherapy. Recently, flaxseed has been approved as a nutrient that lowers blood lipids. Several metabolites of flaxseed lignan secoisolariciresinol diglucoside (SDG), have been identified that reduce blood lipids. SDG is present in flaxseed hull as an ester-linked copolymer with 3-hydroxy-3-methylglutaric acid (HMGA). However, purification processes involved in hydrolysis of the copolymer and enriching SDG are often expensive. The natural copolymer of SDG with HMGA (SDG polymer) is a source of bioactive compounds useful in prophylaxis of hypercholesterolemia. After consumption of the lignan copolymer, SDG and HMGA are released in the stomach and small intestines. SDG is metabolized to secoisolariciresinol, enterolactone and enterodiol, the bioactive forms of mammalian lignans. These metabolites are then distributed throughout the body where they accumulate in the liver, kidney, skin, other tissues, and organs. Successively, these metabolites reduce blood lipids including cholesterol, triglycerides, low density lipoprotein cholesterol, and lipid peroxidation products. In this review, the metabolism and efficacies of flaxseed-derived enriched SDG and SDG polymer will be discussed.

Hypocholesterolemic Efficacy of Secoisolariciresinol Diglucoside and Its Polymer in Rat

Hypercholesterolemia is a risk factor for cardiovascular disease. Conventional treatment methods include lifestyle changes and pharmaceutical interventions, but recently Health Canada approved a health claim for whole ground flaxseed as an alternative treatment for hypercholesterolemia. The literature suggests flaxseed lignans are responsible for the cholesterol-reducing effects of flaxseed. In this study, 96.1% secoisolariciresinol diglucoside (SDG) and a 50% SDG enriched polymer (SDG polymer) were investigated as treatments for hypercholesterolemia in rats. Wistar female rats were fed a 1% high-cholesterol diet for a one-week acclimatization prior to a 23-day intervention with enriched SDG or SDG polymer. A reduction in body weight normalized liver weight was observed in rats treated with enriched SDG when compared to the controls. Both enriched SDG (96.1%) and SDG polymer reduced serum triacylglycerol (19% and 15%, respectively) and increased high-density lipoprotein cholesterol (15% and 24%, respectively). Histopathologic analyses revealed lipid-lowering effects of either enriched SDG or SDG polymer along with lower steatosis scores and nonalcoholic fatty liver disease activity. Furthermore, the lack of statistical significance between SDG and SDG polymer treatment groups suggests that SDG polymer may be a potential alternative to enriched SDG for hypercholesterolemia with similar efficacy but lower cost.

Effect of flaxseed consumption on central obesity, serum lipids, and adiponectin level in overweight or obese women: A randomised controlled clinical trial

BACKGROUND

Flaxseed may be beneficial for the management of obesity due to its high content of alpha-linolenic acid, fibre, and lignans.

OBJECTIVE

We aim to evaluate the effect of flaxseed consumption on serum lipids, adiponectin, leptin, and anthropometric indices in overweight or obese women.

METHODS

This randomised controlled clinical trial involved 60 overweight or obese women. Participants were randomly allocated into two groups: (a) a balanced diet plus 30 g/day milled flaxseed (as treatment group) and (b) a balanced diet plus 30 g/day milled rice (as control group). Anthropometric indices, serum lipids, leptin, and adiponectin level were measured at baseline and at the end of intervention after 12 weeks.

RESULTS

After 12 weeks of intervention, there was significantly higher reduction rate in waist circumference (WC) and waist-to-hip ratio (WHR) (both P < .05) in the flaxseed-consuming group compared with the control group. Moreover, adiponectin level was significantly increased from (12.11 ± 7.1) to (17.15 ± 6.1) in the flaxseed-consuming group compared with the control group from (12.48 ± 4.7) to (12.01 ± 5.8) (P = .002). However, no significant difference was observed in serum lipid level in the study groups before and after the intervention (all P > .05).

CONCLUSION

Flaxseed consumption may improve adiposity markers, such as adiponectin level. Thus, flaxseed consumption could be an adjunctive therapy to attenuate central obesity. Serum lipid profile has not changed meaningfully after flaxseed consumption.

Selected 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase inhibitors. A look into their use and potential in pre-diabetes and type 2 diabetes

Objectives. This review assesses the comparative safety and efficacy of selected 3-hydroxy-3-methylglutaric acid coenzyme A inhibitors (statins, cinnamic acids. 3-hydroxy-3-methyl glutaric acid) on the pre-onset type 2 diabetes (PT2D) and post-onset type 2 diabetes (T2D)-related cluster of seven features (central obesity, hyperglycemia, hypertension, dyslipidemia, pro-thrombosis, oxidation and inflammation). Methods. Google scholar and PubMed were searched for statin*, flaxseed lignan complex (FLC), cinnamic acid (CA)*, and 3-hydroxy-3-methylglutaric acid (HMGA) in conjunction with each of PT2D, T2D and the cluster of seven. An introduction was followed by findings or absence thereof on the impacts of each of statins, FLC, CAs and HMGA on each member of the cluster of seven. Results. Pravastatin manages three features in PT2D, while a number of the statins improve five in T2D. FLC is negative in PT2D but controls four in T2D; it is not clear if the CAs and HMGA in FLC play a role in this success. CAs have potential in six and HMGA has potential in three of the cluster of seven though yet CAs and HMGA are untested in PT2D and T2D in humans. There are safety concerns with some statins and HMGA but FLC and CAs appear safe in the doses and durations tested. Conclusions. Selected statins, FLC, CAs and HMGA can manage or have a potential to manage at least three features of the cluster of seven. Most of the literature-stated concerns are with select statins but there are concerns (one actual and two potential) with HMGA.

Oral Pharmacokinetics of Enriched Secoisolariciresinol Diglucoside and Its Polymer in Rats

Secoisolariciresinol diglucoside (SDG) is the principal lignan of flaxseed and precursor of its aglycone, secoisolariciresinol (SECO), and the mammalian lignans enterolactone (EL) and enterodiol (ED), the putative bioactive forms of oral administration of SDG. SDG is present in the seed hull as an ester-linked polymer. Although extraction and purification of SDG monomer is costly, the use of naturally occurring SDG in polymer form may offer a more economical approach for delivery of this precursor. The extent of SDG release from the polymer and subsequent bioavailability of SDG metabolites are unknown. To understand the relative bioavailability of SDG polymer, this study examined the comparative bioavailability of enriched SDG and SDG polymer in rats after a single oral SDG equivalent dose (40 mg/kg). A validated LC-MS/MS method quantified SDG and its metabolites in rat plasma following serial blood collections. SDG remained undetectable in rat plasma samples. Unconjugated SECO was detected in plasma after 0.25 h. Unconjugated ED was observed after 8 h (3.4 ± 3.3 ng/mL) and 12 h (6.2 ± 3.3 ng/mL) for enriched SDG and SDG polymer, respectively. Total (conjugated and unconjugated) ED and EL resulting from enriched SDG and SDG polymer reached similar maximal concentrations between 11 and 12 h and demonstrated similar total body exposures (AUC values). These data suggest a similar pharmacokinetic profile between the enriched and polymer form of SDG, providing support for the use of SDG polymer as a more economical precursor for SECO, ED, and EL in applications of chronic disease management.

Lignans' Potential in Pre and Post-onset Type 2 Diabetes Management

INTRODUCTION

Type 2 Diabetes (T2D) cases continue to rise dramatically despite efforts to get people to exercise and eat with a view to health and combatting the cluster of 7 issues (central obesity (elevated waist circumference), hyperglycaemia, hypertension, dyslipidemia, pro-thrombotic state, increased oxidation (including Low-density Lipoprotein (LDL)) and the pro-inflammatory state associated with pre- and post-onset T2D.

BACKGROUND

There are numerous medications available to deal with these seven major issues. However, each medication currently available manages a maximum of two cluster members at a time. Consequently, polypharmacy is frequently required to manage the cluster of seven. Polypharmacy brings with it high financial costs for numerous medications, the risk of poor compliance (particularly so in older patients), side effects and drug interactions. Thus, there is a search for new agents that reduce the high costs and risks of polypharmacy while at the same time combatting three or more of the cluster of seven. There is very limited evidence to suggest that one or more lignans may efficaciously and safely, in the short and long term, manage at least three of the cluster of seven, pre- and post-T2D onset, thus reducing polypharmacy. However, multi-centre, large clinical trials are required before any definitive conclusions about these lignans can be reached regarding their safe and efficacious polypharmacy reduction potential, both long and short-term, in pre and post-onset T2D management.

CONCLUSION

It is concluded that some lignans appear to have the potential to manage at least three members of the cluster of seven in pre- or post-T2D onset and hence reduce polypharmacy but much more investigation is required to confirm if such is the case. At the moment, there is not enough evidence that any of the lignans will, in the long or short term, safely and efficaciously manage the cluster of seven via polypharmacy reduction.

Synthetic secoisolariciresinol diglucoside (LGM2605) inhibits myeloperoxidase activity in inflammatory cells

BACKGROUND

Myeloperoxidase (MPO) generates hypochlorous acid (HOCl) during inflammation and infection. We showed that secoisolariciresinol diglucoside (SDG) scavenges radiation-induced HOCl in physiological solutions. However, the action of SDG and its synthetic version, LGM2605, on MPO-catalyzed generation of HOCl is unknown. The present study evaluated the effect of LGM2605 on human MPO, and murine MPO from macrophages and neutrophils.

METHODS

MPO activity was determined fluorometrically using hypochlorite-specific 3'-(p-aminophenyl) fluorescein (APF). The effect of LGM2605 on (a) the peroxidase cycle of MPO was determined using Amplex Red while the effect on (b) the chlorination cycle was determined using a taurine chloramine assay. Using electron paramagnetic resonance (EPR) spectroscopy we determined the effect of LGM2605 on the EPR signals of MPO. Finally, computational docking of SDG was used to identify energetically favorable docking poses to enzyme's active site.

RESULTS

LGM2605 inhibited human and murine MPO activity. MPO inhibition was observed in the absence and presence of Cl-. EPR confirmed that LGM2605 suppressed the formation of Compound I, an oxoiron (IV) intermediate [Fe(IV)O] containing a porphyrin π-radical of MPO's catalytic cycle. Computational docking revealed that SDG can act as an inhibitor by binding to the enzyme's active site.

CONCLUSIONS

We conclude that LGM2605 inhibits MPO activity by suppressing both the peroxidase and chlorination cycles. EPR analysis demonstrated that LGM2605 inhibits MPO by decreasing the formation of the highly oxidative Compound I. This study identifies a novel mechanism of LGM2605 action as an inhibitor of MPO and indicates that LGM2605 may be a promising attenuator of oxidant-dependent inflammatory tissue damage.

The Effect of Short-term Treatment with Fennel on Lipid Profile in Postmenopausal Women: A Randomized Controlled Trial

Objectives

The present trial aimed to assess the effects of Fennel (Foeniculum vulgare Mill.) on lipid profiles.

Methods

In this double blind, randomized and placebo-controlled trial, sixty eligible postmenopausal women were randomly assigned into the fennel and placebo groups. Total blood cholesterol, cholesterol fractions, and triglycerides were tested at the baseline, and after three-month follow-up.

Results

There was no significant difference in triglyceride (P = 0.679), total cholesterol (P = 0.103), low-density lipoprotein cholesterol (LDL-C; P = 0.146) and high-density lipoprotein cholesterol (HDL-C; P = 0.266) levels between the two groups. In addition, in both groups, a paired t.test showed no significant difference in all mentioned parameters, except for HDL-C, indicating significant borderline improvement (P = 0.052) in the fennel group.

Conclusions

The fennel group revealed a very slight positive change in LDL-C, triglyceride and HDL-C. Further studies with longer durations, higher doses, and larger sample sizes are recommended to validate the results.

Flaxseed: its bioactive components and their cardiovascular benefits

Cardiovascular disease remains the leading cause of mortality and morbidity worldwide. The inclusion of functional foods and natural health products in the diet are gaining increasing recognition as integral components of lifestyle changes in the fight against cardiovascular disease. Several preclinical and clinical studies have shown the beneficial cardiovascular effects of dietary supplementation with flaxseed. The cardiovascular effects of dietary flaxseed have included an antihypertensive action, antiatherogenic effects, a lowering of cholesterol, an anti-inflammatory action, and an inhibition of arrhythmias. Its enrichment in the ω-3 fatty acid α-linolenic acid and the antioxidant lignan secoisolariciresinol diglucoside as well as its high fiber content have been implicated primarily in these beneficial cardiovascular actions. Although not as well recognized, flaxseed is also composed of other potential bioactive compounds such as proteins, cyclolinopeptides, and cyanogenic glycosides, which may also produce biological actions. These compounds could also be responsible for the cardiovascular effects of flaxseed. This article will not only summarize the cardiovascular effects of dietary supplementation with flaxseed but also review its bioactive compounds in terms of their properties, biological effects, and proposed mechanisms of action. It will also discuss promising research directions for the future to identify additional health-related benefits of dietary flaxseed.

Secoisolariciresinol diglucoside is a blood-brain barrier protective and anti-inflammatory agent: implications for neuroinflammation

BACKGROUND

Secoisolariciresinol diglucoside (SDG), the main lignan in flaxseed, is known for its beneficial effects in inflammation, oxidative stress, heart disease, tumor progression, atherosclerosis, and diabetes. SDG might be an attractive natural compound that protects against neuroinflammation. Yet, there are no comprehensive studies to date investigating the effects of SDG on brain endothelium using relevant in vivo and in vitro models.

METHODS

We evaluated the effects of orally administered SDG on neuroinflammatory responses using in vivo imaging of the brain microvasculature during systemic inflammation and aseptic encephalitis. In parallel, the anti-inflammatory actions of SDG on brain endothelium and monocytes were evaluated in vitro blood-brain barrier (BBB) model. Multiple group comparisons were performed by one-way analysis of variance with Dunnet's post hoc tests.

RESULTS

We found that SDG diminished leukocyte adhesion to and migration across the BBB in vivo in the setting of aseptic encephalitis (intracerebral TNFα injection) and prevented enhanced BBB permeability during systemic inflammatory response (LPS injection). In vitro SDG pretreatment of primary human brain microvascular endothelial cells (BMVEC) or human monocytes diminished adhesion and migration of monocytes across brain endothelial monolayers in conditions mimicking CNS inflammatory responses. Consistent with our in vivo observations, SDG decreased expression of the adhesion molecule, VCAM1, induced by TNFα, or IL-1β in BMVEC. SDG diminished expression of the active form of VLA-4 integrin (promoting leukocyte adhesion and migration) and prevented the cytoskeleton changes in primary human monocytes activated by relevant inflammatory stimuli.

CONCLUSION

This study indicates that SDG directly inhibits BBB interactions with inflammatory cells and reduces the inflammatory state of leukocytes. Though more work is needed to determine the mechanism by which SDG mediates these effects, the ability of SDG to exert a multi-functional response reducing oxidative stress, inflammation, and BBB permeability makes it an exciting potential therapeutic for neuroinflammatory diseases. SDG can serve as an anti-inflammatory and barrier-protective agent in neuroinflammation.

The effect of flaxseed supplementation on body weight and body composition: a systematic review and meta-analysis of 45 randomized placebo-controlled trials

Flaxseed consumption may be inversely associated with obesity; however, findings of available randomized controlled trials (RCTs) are conflicting. The present study aimed to systematically review and analyse RCTs assessing the effects of flaxseed consumption on body weight and body composition. PubMed, Medline via Ovid, SCOPUS, EMBASE and ISI Web of Sciences databases were searched up to November 2016. Mean changes in body composition indices including body weight, body mass index (BMI) and waist circumference were extracted. Effect sizes were expressed as weighted mean difference (WMD) and 95% confidence intervals (CI). Heterogeneity between studies was assessed with the I² test. Publication bias and subgroup analyses were also performed. The quality of articles was assessed via the Jadad scale. A total of 45 RCTs were included. Meta-analyses suggested a significant reduction in body weight (WMD: -0.99 kg, 95% CI: -1.67, -0.31, p = 0.004), BMI (WMD: -0.30 kg m^-2 , 95% CI: -0.53, -0.08, p = 0.008) and waist circumference (WMD: -0.80 cm, 95% CI: -1.40, -0.20, p = 0.008) following flaxseed supplementation. Subgroup analyses showed that using whole flaxseed in doses ≥30 g d^-1 , longer-term interventions (≥12 weeks) and studies including participants with higher BMI (≥ 27 kg m^-2 ) had positive effects on body composition. Whole flaxseed is a good choice for weight management particularly for weight reduction in overweight and obese participants.

Enterolactone has stronger effects than enterodiol on ovarian cancer

Background

Ovarian cancer is one of the three leading gynecological malignancies, characterized by insidious growth, highly frequent metastasis, and quick development of drug resistance. As a result, this disease has low 5-year survival rates. Estrogen receptor inhibitors were commonly used for the treatment, but only 7% to 18% of patients respond to anti-estrogen therapies. Therefore, more effective therapies to inhibit estrogen-related tumors are urgently needed. Recently, phytoestrogens, such as lignans with estrogen-like biological activities, have attracted attention for their potential effects in the prevention or treatment of estrogen-related diseases. Enterodiol (END) and enterolactone (ENL) are mammalian lignans, which can reduce the risk of various cancers. However, the effects of END and ENL on ovarian cancer are not adequately documented.

Methods

We used in vitro assays on the ES-2 cell line to evaluate the inhibiting effects of END and ENL on ovarian cancer cell proliferation, invasion and migration ability and in vivo xenograft experiments on nude mice to validate the anticancer effects of END and ENL.

Results

The in vitro assays demonstrated that high-dose END and ENL could obviously inhibit ovarian malignant properties, including cancerous proliferation, invasion, and metastasis. Compared to END, ENL behaved in a better time-dose dependent manner on the cancer cells. The in vivo experiments showed that END (1 mg/kg), ENL (1 mg/kg) and ENL (0.1 mg/kg) suppressed tumor markedly, and there were statistically significant differences between the experimental and control groups in tumor weight and volume. Compared to END, which have serious side effects to the animals at high concentration such as 1 mg/kg, ENL had higher anticancer activities and less side effects in the animals than END at the same concentrations, so it would be a better candidate for drug development.

Conclusion

END and ENL both have potent inhibitory effects on ovarian cancer but ENL possesses a more effective anti-cancer capability and less side effects than END. Findings in this work provide novel insights into ovarian cancer therapeutics with phytoestrogens and encourage their clinical applications.

Enterolactone Reduces Telomerase Activity and The Level of Its Catalytic Subunit in Breast Cancer Cells

OBJECTIVE

There is a positive correlation between higher serum phytoestrogen concentrations and lower risk of breast cancer. The activation of telomerase is crucial for the growth of cancer cells; therefore, the aim of this study was to examine the effects of enterolactone (ENL) and enterodiol (END) on this enzyme.

MATERIALS AND METHODS

In this experimental study, we performed the viability assay to determine the effects of different concentrations of ENL and END on cell viability, and the effective concentrations of these two compounds on cell growth. We used western blot analysis to evaluate human telomerase reverse transcriptase catalytic subunit (hTERT) expression and polymerase chain reaction (PCR)-ELISA based on the telomeric repeat amplification protocol (TRAP) assay for telomerase activity.

RESULTS

Both ENL and END, at 100 μM concentrations, significantly (P<0.05) reduced cell viability. However, only the 100 μM concentration of ENL significantly (P<0.05) decreased hTERT protein levels and telomerase activity. Lower concentrations of ENL did not have any significant effects on telomerase activity and hTERT protein levels.

CONCLUSION

High concentration of ENL decreased the viability of MCF-7 breast cancer cells and inhibited the expression and activity of telomerase in these cells. Although END could reduce breast cancer cell viability, it did not have any effect on telomerase expression and activity.

Effect of Antibiotics and Diet on Enterolactone Concentration and Metabolome Studied by Targeted and Nontargeted LC-MS Metabolomics

High plant lignan intake is associated with a number of health benefits, possibly induced by the lignan metabolite enterolactone (ENL). The gut microbiota plays a crucial role in converting dietary lignans into ENL, and epidemiological studies have shown that use of antibiotics is associated with lower levels of ENL. Here we investigate the link between antibiotic use and lignan metabolism in pigs using LC-MS/MS. The effect of lignan intake and antibiotic use on the gut microbial community and the pig metabolome is studied by 16S rRNA sequencing and nontargeted LC-MS. Treatment with antibiotics resulted in substantially lower concentrations of ENL compared with concentrations detected in untreated animals, whereas the plasma concentrations of plant lignans were unchanged. Both diet and antibiotic treatment affected the clustering of urinary metabolites and significantly altered the proportions of taxa in the gut microbiota. Diet, but not antibiotic treatment, affected the plasma lipid profile, and a lower concentration of LDL cholesterol was observed in the pigs fed a high lignan diet. This study provides solid support for the associations between ENL concentrations and use of antibiotics found in humans and indicates that the lower ENL concentration may be a consequence of the ecological changes in the microbiota.

Enterolactone Induces G1-phase Cell Cycle Arrest in Nonsmall Cell Lung Cancer Cells by Downregulating Cyclins and Cyclin-dependent Kinases

Flaxseed is a rich source of the plant lignan secoisolariciresinol diglucoside (SDG), which is metabolized into mammalian lignans enterodiol (ED) and enterolactone (EL) in the digestive tract. The anticancer properties of these lignans have been demonstrated for various cancer types, but have not been studied for lung cancer. In this study, we investigated the anticancer effects of EL for several nonsmall cell lung cancer (NSCLC) cell lines of various genetic backgrounds. EL inhibited the growth of A549, H441, and H520 lung cancer cells in concentration- and time-dependent manners. The antiproliferative effects of EL for lung cancer cells were not due to enhanced cell death, but rather due to G1-phase cell cycle arrest. Molecular studies revealed that EL decreased mRNA or protein expression levels of the G1-phase promoters cyclin D1, cyclin E, cyclin-dependent kinases (CDK)-2, -4, and -6, and p-cdc25A; decreased phosphorylated retinoblastoma (p-pRb) protein levels; and simultaneously increased levels of p21WAF1/CIP1, a negative regulator of the G1 phase. The results suggest that EL inhibits the growth of NSCLC cell lines by downregulating G1-phase cyclins and CDKs, and upregulating p21WAF1/CIP1, which leads to G1-phase cell cycle arrest. Therefore, EL may hold promise as an adjuvant treatment for lung cancer therapy.

The effect of flaxseed powder on insulin resistance indices and blood pressure in prediabetic individuals: A randomized controlled clinical trial

BACKGROUND

Designing the effective and early interventions can prevent progression of prediabetes to diabetes. Few studies have shown the effect of flaxseed on glycemic control. This study aimed to assess the effect of flaxseed powder on insulin resistance (IR) indices and blood pressure in prediabetic individuals.

MATERIALS AND METHODS

In a randomized clinical trial, 99 prediabetic individuals were randomly divided into three groups: two groups received 40 g (FG40) and 20 g (FG20) flaxseed powder daily for 12 weeks and the third group was the control (CG). Before and after the intervention, anthropometric measurements, blood pressure, fasting serum glucose (FSG), insulin, homeostasis model assessment IR index (HOMA-IR), beta-cell function, and insulin sensitivity were measured.

RESULTS

FSG significantly declined overall in all groups compared to the baseline (P = 0.002 in CG and FG20 groups and P = 0.001 in FG40). In contrast, mean of the changes in FSG was not significantly different between groups. Insulin concentration did not change significantly within and between the investigated groups. Although HOMA-IR reduced in FG20 (P = 0.033), the mean of changes was not significant between the three groups. Mean of beta-cell function increased in CG and FG40 groups compared to the baseline (P = 0.044 and P = 0.018, respectively), but mean of its changes did not show any difference between the three groups. The mean of changes in IR indices was not significant between the three groups. FG40 group had significantly lowered systolic blood pressure after the intervention (P = 0.005).

CONCLUSION

Daily intake of flaxseed powder lowered blood pressure in prediabetes but did not improve glycemic and IR indices.

Reduced endogenous urinary total antioxidant power and its relation of plasma antioxidant activity of superoxide dismutase in individuals with autism spectrum disorder

Individuals with autism spectrum disorders (ASD) have impaired detoxification capacity. Investigating　the neurobiological bases of　impaired antioxidant capacity is thus a research priority in the pathophysiology of ASD.　We measured　the urinary levels of hexanoyl-lysine (HEL) which is a new oxidative stress　biomarker, total antioxidant power (TAP) and DNA methylation biomarker 8-hydroxy-2'-deoxyguanosine (8-OHdG), and the plasma levels of superoxide dismutase (SOD), which is a major antioxidant enzyme. We examined whether the urinary levels of these enzymes and biomarkers may be related to symptoms of social impairment in 20 individuals with ASD (meanage,11.1±5.2years) and 12 age- and gender-matched healthy controls (meanage,14.3±6.2years). Symptoms of social impairment were　assessed using the Social Responsiveness Scale (SRS). The dietary TAP of the fruit juice, chocolate, cookies, biscuits, jam and marmalade were significantly higher in the ASD group than in the control group, although the intake of nutrients was not significantly different between the groups. The urinary TAP levels were significantly lower in the ASD group than in the control group. There were no significantly differences in urinary HEL and 8-OHdG levels between the ASD and control groups. The SRS scores were significantly higher in the ASD group than in the control group. Stepwise regression analysis revealed that urinary TAP levels and plasma SOD levels can differences in the biomarkers and the SRS scores between the ASD group and the control group. The endogenous antioxidant capacity may be deficient without altered urinary HEL and 8-OHdG levels in individuals with ASD. The plasma SOD levels may be related to reduced endogenous antioxidant capacity.

Effects of consumption of whole grain foods rich in lignans in healthy postmenopausal women with moderate serum cholesterol: a pilot study

This study aims at investigating the effect of an experimental period of intake of whole grain foods rich in lignans as part of an habitual diet on the plasma and urinary excretion of enterolignans, the biomarkers of lipid metabolism and the immunological and antioxidant status in a group of postmenopausal women with moderate serum cholesterol. A randomized double-blind crossover study was completed on 13 subjects in 12-weeks after protocol approval of an ethical committee. The subjects consumed whole grain foods high in lignans (30 g/d of breakfast cereals or biscuits, etc., 80 g/d of whole grain pasta) or refined grain foods for 4 weeks, separated by a 2-weeks wash-out period. A modest hypocholesterolemic effect (p < 0.05) of the whole grain diet was observed and the intake of whole grain products rich in lignans was also associated with an increase in urinary enterodiol excretion (p < 0.05).

Flaxseed reverses atherosclerotic lesion formation and lowers lipoprotein(a) in ovarian hormone deficiency

OBJECTIVE

The incidence of cardiovascular disease dramatically increases during menopause, and postmenopausal women seek natural alternatives to hormone therapy. Flaxseed can slow the progression of atherosclerotic lesion formation; however, it is not known whether it can reverse formation that has already occurred.

METHODS

Seventy-two female Golden Syrian hamsters were randomly divided into six groups (n = 12), sham-operated (sham) or ovariectomized (ovx), and kept on the same diet for 120 days to allow for atherosclerotic lesion development. After this 120-day period, whole flaxseed was introduced to the diets of hamsters in three of the groups: group 1 (sham + casein); group 2 (ovx + casein); group 3 (ovx + 7.5% flaxseed); group 4 (ovx + 15% flaxseed); group 5 (ovx + 22.5% flaxseed); and group 6 (ovx + 17β-estradiol). This diet was maintained for an additional 120 days. Lesion regression was examined histologically, and serum was analyzed for total cholesterol, triglyceride, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, Apo A, Apo B, and lipoprotein(a).

RESULTS

Results showed that 15% and 22.5% flaxseed, compared with ovx animals, significantly reduced lipoprotein(a) (4.4 mg/dL [ovx] vs 2.15 mg/dL [15% flaxseed] and 0.3 mg/dL [22.5% flaxseed]; P < 0.05) and Apo B (2.8 mg/dL [ovx] vs 2.4 mg/dL [15% flaxseed] and 2.5 mg/dL [22.5% flaxseed]). Flax reduced by 67% the number of animals with aortic arch lesions.

CONCLUSIONS

All three doses of flax reduce the severity of lesion formation compared with ovx controls. These results support the efficacy of flaxseed in reducing cardiovascular disease risk.

Flaxseed lignan complex administration in older human type 2 diabetics manages central obesity and prothrombosis-an invitation to further investigation into polypharmacy reduction

Aim. Animal and human study evidence supports the hypothesis that flaxseed lignan complex (FLC) at a dose of 600 mg secoisolariciresinol diglucoside (SDG)/day for three months would combat hyperglycaemia, dyslipidemia, blood pressure, central obesity, prothrombotic state, inflammation, and low density lipoprotein (LDL) oxidation. Methods. Sixteen type 2 diabetic patients completed this double-blind, randomised crossover placebo-controlled study. A univariate repeated measures analysis of covariance (significance P < 0.05) was followed by a mixed linear model effects analysis corrected for multiple comparisons (MCC). Results. Prior to MCC, FLC caused decreased fasting plasma glucose, A1c, inflammation (c-reactive protein (CRP) and interleukin-6 (IL-6)), and increased bleeding time. After correction for multiple comparisons, FLC induced a statistically significant increase in bleeding time and smaller waist circumference gain. No treatment effect occurred in the other variables before or after adjustment. Conclusions. It is concluded that FLC significantly increased bleeding time thus reducing the prothrombotic state, reduced central obesity gain as measured by waist circumference, and did not affect significantly the other dependent variables measured after adjustment for multiple comparisons. These findings, not yet published in human type 2 diabetes, suggest that this FLC dose over at least three months, may, subject to further investigation, reduce polypharmacy.

Vascular effects of phytoestrogens and alternative menopausal hormone therapy in cardiovascular disease

Phytoestrogens are estrogenic compounds of plant origin classified into different groups including isoflavones, lignans, coumestans and stilbenes. Isoflavones such as genistein and daidzein are the most studied and most potent phytoestrogens, and are found mainly in soy based foods. The effects of phytoestrogens are partly mediated via estrogen receptors (ERs): ERα, ERβ and possibly GPER. The interaction of phytoestrogens with ERs is thought to induce both genomic and non-genomic effects in many tissues including the vasculature. Some phytoestrogens such as genistein have additional non-ER-mediated effects involving signaling pathways such as tyrosine kinase. Experimental studies have shown beneficial effects of phytoestrogens on endothelial cells, vascular smooth muscle, and extracellular matrix. Phytoestrogens may also affect other pathophysiologic vascular processes such as lipid profile, angiogenesis, inflammation, tissue damage by reactive oxygen species, and these effects could delay the progression of atherosclerosis. As recent clinical trials showed no vascular benefits or even increased risk of cardiovascular disease (CVD) and CV events with conventional menopausal hormone therapy (MHT), phytoestrogens are being considered as alternatives to pharmacologic MHT. Epidemiological studies in the Far East population suggest that dietary intake of phytoestrogens may contribute to the decreased incidence of postmenopausal CVD and thromboembolic events. Also, the WHO-CARDIAC study supported that consumption of high soybean diet is associated with lower mortalities from coronary artery disease. However, as with estrogen, there has been some discrepancy between the experimental studies demonstrating the vascular benefits of phytoestrogens and the data from clinical trials. This is likely because the phytoestrogens clinical trials have been limited in many aspects including the number of participants enrolled, the clinical end points investigated, and the lack of long-term follow-up. Further investigation of the cellular mechanisms underlying the vascular effects of phytoestrogens and careful evaluation of the epidemiological evidence and clinical trials of their potential vascular benefits would put forward the use of phytoestrogens as an alternative MHT for the relief of menopausal symptoms and amelioration of postmenopausal CVD.

Qualitative and quantitative analysis of the major phenolic compounds as antioxidants in barley and flaxseed hulls using HPLC/MS/MS

BACKGROUND

Both qualitative and quantitative analyses of the major phenolic compounds in barley and flaxseed hulls were conducted using reverse phase high-performance liquid chromatography coupled with photodiode array detection and quadrupole time-of-flight mass spectrometry.

RESULTS

Ferulic acid, p-coumaric acid, vanillic acid and vanillin were identified and quantified in four barley hull samples. Four ferulate dehydrodimers were also detected. The phenolic compounds of flaxseed hull were distinct from those of barley hull. Three flaxseed hull samples varied significantly (P < 0.05) in their contents of secoisolariciresinol diglucoside (16.38-33.92 g kg(-1) ), coumaric acid glucoside (35.68-49.22 g kg(-1) ) and ferulic acid glucoside (5.07-15.23 g kg(-1) ). The phytochemical profiles of co-extracts featured the major phenolic compounds from both barley and flaxseed hulls. The total phenolic content and 2,2-diphenyl-1-picrylhydrazyl radical-scavenging capacity varied significantly (P < 0.05) among different varieties of flaxseed and barley hulls.

CONCLUSION

As agricultural by-products, barley and flaxseed hulls may be utilised as potential sources of functional food ingredients through extraction and concentration of the phytochemicals identified above.

The protective effect of flaxseed oil on lead acetate-induced renal toxicity in rats

Lead is a toxic metal inducing many destructive effects leading to a broad range of physiological, biochemical, and neurological dysfunctions in humans. Here, we investigated the effects of flaxseed oil (1000 mg/kg) on the outcome of renal cytotoxicity induced by lead acetate (20mg/kg) in male rats. Lead induced injury of the renal tissue. This was evidenced (i) as increases in lead concentration in the kidney, (ii) as increases in the histopathological damage of the renal tissue, (iii) as increases in uric acid, urea and creatinine, (iv) as increases in lipid peroxidation, nitric oxide and reactive oxygen species, and (v) as lowered glutathione levels and decreased activities of catalase and superoxide dismutase, glutathione reductase, glutathione-S-transferase, and glutathione peroxidase, respectively. All these lead-induced parameters were significantly altered during flaxseed oil treatment. Therefore, our study suggests the role of flaxseed oil in limiting renal cytotoxicity-induced by lead acetate as a model for lead toxicity.

Effects of a safflower tea supplement on antioxidative status and bone markers in postmenopausal women

We conducted this study to examine the effects of safflower seed granular tea containing physiologically active polyphenols on antioxidative activities and bone metabolism. Forty postmenopausal women ages 49 to 64-years were recruited from Daegu and Gyeongbuk and were randomly assigned to either a safflower tea supplement (Saf-tea) group (n = 27) or a placebo group (n = 13). The Saf-tea group received 20 g of safflower seed granule tea per day containing a 13% ethanol extract of defatted safflower seeds, whereas the placebo group received a similar type of tea that lacked the ethanol extract. No significant changes in nutrient intake for either the placebo or Saf-tea groups were observed before or after the study period, except vitamin A intake increased after 6 months in the Saf-tea group. Dietary phytoestrogen intakes were similar in the Saf-tea group (60.3 mg) and placebo group (52.5 mg). Significant increases in plasma genistein and enterolactone were observed in the Saf-tea group. After 6 months of supplementation, serum levels of antioxidant vitamins such as α-tocopherol and ascorbic acid increased significantly, and TBARS levels decreased in the Saf-tea group compared to the placebo group. Serum osteocalcin levels were reduced (P < 0.05) in the Saf-tea group after 6 months, whereas serum osteocalcin did not change in the placebo group. Urinary deoxypyridinoline/creatinine excretion was not different between the two groups at baseline, and did not change in either group after 6 months. Bone mineral density decreased significantly in the placebo group (P < 0.01) but not in the supplemented group. It was concluded that polyphenols (72 mg/day), including serotonin derivatives, in the Saf-tea had both antioxidant and potential bone protecting effects in postmenopausal women without liver toxicity.

Dietary lignans: physiology and potential for cardiovascular disease risk reduction

The present review of the literature on lignan physiology and lignan intervention and epidemiological studies was conducted to determine if lignans decrease the risks of cardiovascular disease in Western populations. Five intervention studies using flaxseed lignan supplements indicated beneficial associations with C-reactive protein, and a meta-analysis that included these studies also suggested lignans have a lowering effect on plasma total and low-density lipoprotein cholesterol. Three intervention studies using sesamin supplements indicated possible lipid- and blood pressure-lowering associations. Eleven human observational epidemiological studies examined dietary intakes of lignans in relation to cardiovascular disease risk. Five showed decreased risk with either increasing dietary intakes of lignans or increased levels of serum enterolactone (an enterolignan used as a biomarker of lignan intake), five studies were of borderline significance, and one was null. The associations between lignans and decreased risk of cardiovascular disease are promising, but they are yet not well established, perhaps due to low lignan intakes in habitual Western diets. At the higher doses used in intervention studies, associations were more evident.

Enterodiol and enterolactone modulate the immune response by acting on nuclear factor-kappaB (NF-kappaB) signaling

Lignan-rich whole-grain cereals, beans, berries, and nuts show protective effects against a variety of chronic diseases, including cancer. Lignans are converted by intestinal microflora to enterolactone (EL) and its oxidation product enterodiol (ED). To investigate the immunomodulatory effect of EL and ED in human cells, peripheral blood lymphocytes were treated with increasing physiologically relevant concentrations of EL and ED (0-1000 microM) and stimulated with lipopolysaccharide (LPS) and anti-CD3 plus anti-CD28 monoclonal antibodies. A dose-related inhibition of cell proliferation and cytokine production was observed, with EL being the most active. Molecular investigations in THP-1 cells showed that both EL and ED prevented inhibitory-kappaB (I-kappaB) degradation and nuclear factor-kappaB (NF-kappaB) activation, which in turn resulted in decreased tumor necrosis factor-alpha (TNF-alpha) production. EL and ED were also able to pass the intestinal barrier and modulate cytokine production. The findings of the present study reveal potential mechanisms that could explain some in vivo beneficial effects of lignans.

Health effects with consumption of the flax lignan secoisolariciresinol diglucoside

Flaxseed is the richest source of the lignan secoisolariciresinol diglucoside (SDG). After ingestion, SDG is converted to secoisolariciresinol, which is further metabolised to the mammalian lignans enterodiol and enterolactone. A growing body of evidence suggests that SDG metabolites may provide health benefits due to their weak oestrogenic or anti-oestrogenic effects, antioxidant activity, ability to induce phase 2 proteins and/or inhibit the activity of certain enzymes, or by mechanisms yet unidentified. Human and animal studies identify the benefits of SDG consumption. SDG metabolites may protect against CVD and the metabolic syndrome by reducing lipid and glucose concentrations, lowering blood pressure, and decreasing oxidative stress and inflammation. Flax lignans may also reduce cancer risk by preventing pre-cancerous cellular changes and by reducing angiogenesis and metastasis. Thus, dietary SDG has the potential to decrease the incidence of several chronic diseases that result in significant morbidity and mortality in industrialised countries. The available literature, though, makes it difficult to clearly identify SDG health effects because of the wide variability in study methods. However, the current evidence suggests that a dose of at least 500 mg SDG/d for approximately 8 weeks is needed to observe positive effects on cardiovascular risk factors in human patients. Flaxseed and its lignan extracts appear to be safe for most adult populations, though animal studies suggest that pregnant women should limit their exposure. The present review discusses the potential health benefits of SDG in humans, with supporting evidence from animal studies, and offers suggestions for future research.

Experimental and clinical research findings on the cardiovascular benefits of consuming flaxseed

Functional foods and nutraceuticals are becoming popular alternatives to pharmacological treatments by providing health benefits and (or) reducing the risk of chronic diseases. Flaxseed is a rich source of 3 components with demonstrated cardioprotective effects: the omega-3 fatty acid α-linolenic acid (ALA), dietary fibre, and phytoestrogen lignans. Multiple clinical dietary intervention trials report that consuming flaxseed daily can modestly reduce circulating total cholesterol (TC) by 6%–11% and low-density lipoprotein (LDL) cholesterol by 9%–18% in normolipemic humans and by 5%–17% for TC and 4%–10% for LDL cholesterol in hypercholesterolemic patients, as well as lower various markers associated with atherosclerotic cardiovascular disease in humans. Evidence to date suggests that the dietary fibre and (or) lignan content of flaxseed provides the hypocholesterolemic action. The omega-3 ALA found in the flaxseed oil fraction also contributes to the antiatherogenic effects of flaxseed via anti-inflammatory and antiproliferative mechanisms. Dietary flaxseed may also protect against ischemic heart disease by improving vascular relaxation responses and by inhibiting the incidence of ventricular fibrillation.

Meta-analysis of the effects of flaxseed interventions on blood lipids

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.

A randomized controlled trial of the effects of flaxseed lignan complex on metabolic syndrome composite score and bone mineral in older adults

A randomized double-blind placebo controlled study design was used to assess the effects of flaxseed lignan complex supplementation during exercise training on a metabolic syndrome composite score and osteoporosis risk in older adults. A total of 100 subjects (>or=50 years) were randomized to receive flaxseed lignan (543 mg.day-1 in a 4050 mg complex) or placebo while completing a 6 month walking program (30-60 min.day-1, 5-6 days.week-1). Fasting serum glucose, triacylglycerol (TAG), high-density lipoprotein (HDL) cholesterol, low-density lipoprotein cholesterol, total cholesterol, interleukin-6, and tumor necrosis factor-alpha were measured every 2 months, while body composition, bone mineral density, and resting blood pressure were assessed at baseline and at 6 months. A composite Z score of 6 risk factors for metabolic syndrome (fasting glucose, HDL cholesterol, TAG, abdominal adiposity, blood pressure, and inflammatory cytokines) was calculated at baseline and at 6 months. Men taking placebo increased metabolic syndrome composite Z score (p < 0.05), but there were no changes in the other groups. A significant group x sex x time interaction was noted for TAG (p = 0.017) and diastolic blood pressure (p = 0.046), with men taking flaxseed lignan decreasing diastolic blood pressure relative to men taking placebo, and men taking placebo increasing TAG relative to men taking flax lignan. There were no differences between groups for change in bone measures, body composition, lipoproteins, or cytokines. Males taking the flaxseed lignan complex reduced metabolic syndrome score relative to men taking placebo, but a similar trend was not seen in females. Flaxseed lignan had no effect on bone mineral density or content, body composition, lipoproteins, glucose, or inflammation.

Quantitative aspects of the metabolism of lignans in pigs fed fibre-enriched rye and wheat bread

A diet rich in lignans has been suggested to be protective against a range of chronic diseases. The distribution and metabolic fate of lignans is, however, very poorly understood. We fed high-fibre wheat breads low in lignans (n 8) or high-fibre rye breads (n 9) rich in plant lignans to pigs for 58-67 d, and analysed the content of plant lignans and their metabolites in the diet, blood, bile, faeces, urine and selected tissues. Apparent faecal digestibility of dietary precursors was higher than of total (plant- and entero-) lignans due to conversion to enterolactone and enterodiol. The digestibility of lariciresinol and matairesinol was lower than that of the sum of plant lignans. This suggests that interconversion of plant lignans during digestion and enterohepatic circulation occur without complete conversion to enterolignans. The majority of lignans present in plasma and urine was in the form of enterolignans, but up to 23 % in the plasma, and 11 % in the urine of the rye-fed pigs were in the form of plant lignans. There was a very high concentration of lignans in bile from the rye-fed pigs with as much as 77 % in the form of plant lignans. Lignans were detected in the tissue of colon, liver, breast and brain at a much higher level with rye than with wheat, but only in the form of enterolactone. The importance and implications of systemic exposure to plant lignans remain to be elucidated.