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Sdg Flax Lignans

Also known as: SDG, Flax lignans, Flaxseed lignans, SDG lignan complex, Secoisolariciresinol diglucoside

Overview

Secoisolariciresinol diglucoside (SDG) is a plant lignan predominantly found in flaxseed (Linum usitatissimum), which is the richest known dietary source. Upon ingestion, SDG is metabolized by intestinal bacteria into mammalian lignans, specifically enterodiol and enterolactone, which are the biologically active compounds. SDG flax lignans are primarily investigated for their potential benefits in cardiovascular health, cancer risk reduction (particularly breast cancer), anti-inflammatory effects, and metabolic improvements. SDG exhibits antioxidant, anti-inflammatory, and potential hormone-modulating properties. Research on SDG is moderately advanced, with multiple randomized controlled trials (RCTs) and systematic reviews/meta-analyses available. While some high-quality studies support certain benefits, heterogeneity in study designs and outcomes means that some conclusions remain inconclusive. It is classified as a phytoestrogenic polyphenolic compound and is used as a dietary supplement.

Benefits

SDG flax lignans show promising effects, particularly in cancer risk modulation. Randomized trials have indicated potential in reducing breast cancer risk markers; for instance, a study in postmenopausal breast cancer patients showed decreased tumor cell proliferation and HER2 oncogene expression with flaxseed intake. Another trial with 50 mg/day SDG in high-risk premenopausal women demonstrated reduced breast precancerous changes and a decrease in the Ki-67 proliferation marker in 80% of participants. These biomarker reductions are considered clinically relevant. Postmenopausal women and individuals at high risk of breast cancer appear to benefit most. Regarding cardiovascular and inflammatory markers, meta-analyses of RCTs using flaxseed products (including SDG doses of 360-600 mg/day) have not found significant reductions in plasma C-reactive protein (CRP), a key inflammatory biomarker. However, some studies report modest improvements in lipid profiles with flaxseed derivatives. The antioxidant and anti-inflammatory properties of SDG may contribute to broader metabolic and vascular health benefits, though the evidence for these broader effects is less robust. Benefits on cancer biomarkers can be observed within weeks to months, but long-term effects require further study.

How it works

SDG is metabolized by intestinal microbiota into active mammalian lignans, enterodiol and enterolactone, which are then absorbed. These enterolignans exert their biological effects primarily through estrogenic and anti-estrogenic actions by binding to estrogen receptors (ERα and ERβ). This interaction can modulate cell proliferation and apoptosis, particularly relevant in hormone-sensitive tissues. Additionally, SDG and its metabolites exhibit significant antioxidant activity by scavenging free radicals and anti-inflammatory effects by modulating inflammatory cytokines. They may also influence HER2 oncogene expression. The primary systems affected are the endocrine (hormonal), immune, and cardiovascular systems. The conversion by gut microbiota is crucial for SDG's bioavailability and subsequent systemic effects.

Side effects

SDG flax lignans are generally well tolerated, with no serious adverse events reported in randomized controlled trials lasting up to 12 months. The most common side effects are mild gastrointestinal symptoms, such as bloating and gas, which are reported in less than 5% of users. No uncommon or rare severe side effects have been significantly reported. Due to its phytoestrogenic activity, there is a potential for interactions with hormone therapies, and caution is advised for individuals with hormone-sensitive conditions. SDG is not recommended for patients with known hormone-sensitive cancers without direct medical supervision. The safety of SDG supplementation during pregnancy and lactation has not been well established, and therefore, its use in these populations is not advised without consulting a healthcare professional.

Dosage

The minimum effective dose of SDG lignan for breast cancer risk modulation has been observed at approximately 50 mg/day. Optimal dosage ranges in clinical trials typically fall between 360-600 mg/day of SDG. When consuming whole flaxseed powder, doses of 13-60 g/day correspond to variable SDG content. There is no established upper limit for SDG, but doses up to 600 mg/day have appeared safe in studies. Supplementation is typically taken daily, with benefits observed after weeks to months of consistent use. SDG can be consumed as powdered flaxseed, flaxseed oil, or isolated SDG extracts, with bioavailability potentially varying between forms. Its absorption is dependent on the gut microbiota for conversion into active metabolites. No specific cofactors are required, but overall diet quality may influence its effects.

FAQs

Is SDG flax lignan safe for breast cancer patients?

Evidence suggests potential benefits in reducing tumor proliferation markers, but due to its phytoestrogenic effects, use should be supervised by an oncologist.

How long before effects appear?

Biomarker changes have been observed within 5 weeks to 1 year, depending on the specific outcome being measured.

Does it reduce inflammation?

Meta-analyses of clinical trials have shown no significant effect on C-reactive protein (CRP), a key inflammation marker.

Can it replace hormone therapy?

No, SDG flax lignans may complement conventional treatments but are not a substitute for prescribed hormone therapy.

Research Sources

https://www.archivesofmedicalscience.com/A-systematic-review-and-meta-analysis-of-clinical-trials-investigating-the-effects,74141,0,2.html – This systematic review and meta-analysis of 17 RCTs (1256 participants) investigated the effects of flaxseed/SDG on inflammatory markers. It concluded that flaxseed/SDG, even at doses of 360-600 mg SDG/day, did not significantly change plasma C-reactive protein (CRP) levels. The study noted some unclear bias and heterogeneity among interventions.
https://www.frontiersin.org/journals/nutrition/articles/10.3389/fnut.2018.00004/full – This source discusses randomized controlled trials on flaxseed and SDG in breast cancer. It highlights studies showing reduced tumor proliferation, HER2 expression, and Ki-67 levels with 25g flaxseed or 50mg SDG daily in postmenopausal breast cancer patients and high-risk premenopausal women. While high-quality, the studies had small sample sizes and short durations for cancer outcomes.
https://pmc.ncbi.nlm.nih.gov/articles/PMC8504108/ – This systematic review and dose-response meta-analysis of 33 RCTs examined the effects of flaxseed products on various health markers. It found some improvements in lipid profiles but no consistent changes in inflammatory markers. The study noted variable flaxseed products and moderate heterogeneity among the included trials.