Hydroxymatairesinol (HMR): A Comprehensive Reference
1. Identity and Chemical Characterization
1.1 Names and Classification
Hydroxymatairesinol (HMR) is a lignan found in Norway spruce (Picea abies). Its full systematic name is 7-hydroxymatairesinol, often abbreviated as 7-HMR or HMR. HMR is a lignan — a group of chemical compounds found in plants derived from phenylalanine via dimerization of substituted cinnamic alcohols, known as monolignols, to a dibenzylbutane skeleton. Lignans are defined as a class of phenolic compounds possessing a 2,3-dibenzylbutane skeleton; they are formed by coupling of monomeric units called precursors such as cinnamic acid, caffeic, ferulic, coumaric, and gallic acids.
HMR's chemical structure is similar to matairesinol. The compound exists as two diastereomeric isomers — HMR and HMR2 — both of which have been identified in spruce knot extracts. Lignans are one of the major classes of phytoestrogens, which are oestrogen-like chemicals and also act as antioxidants.
In commerce and research, HMR is most widely encountered as its potassium acetate complex salt, sold under the trademarked name HMRlignan™ (formerly HMR/lignan™ or HM-3000), a proprietary and patent-protected product manufactured and marketed worldwide by Linnea, Switzerland.
1.2 Natural Sources
The novel lignan 7-hydroxymatairesinol was identified and extracted from the heartwood of the Norway spruce, Picea abies. The spruce knots, which are parts of the branches embedded in the stem, consist of 6–16% of lignans, and HMR represents 65–80% of the total lignan content. The far most abundant single component of lignans in spruce is HMR — about 60 percent of total lignans — which occurs mainly in unconjugated free form.
Lignan concentration in thick roots is 2–3 percent; abundant lignans occur in the heartwood of branches (5–10 percent) and especially in the knots, where the amount of lignans may be higher than 10 percent. These concentrations are about hundred-fold compared to ground flax powder known as lignan-rich material.
The typical lignans in heartwood of spruce (Picea abies) include hydroxymatairesinol (HMR), α-conidendrin, conidendrinic acid, matairesinol, isolariciresinol, secoisolariciresinol, liovile, picearesinol, lariciresinol, and pinoresinol.
Beyond Norway spruce, new Finnish research has uncovered the naturally occurring existence of 7-hydroxymatairesinol as the dominant lignan in wheat, triticale, barley, corn, amaranth, millet, and oat bran. However, prior to this research, the lignan was known to be found in Norway spruce (Picea abies), which still remains the most potent, and hence economically viable source for manufacture into dietary supplements and functional foods.
1.3 Common Forms and Preparations
The spruce knots consist of 6–16% of lignans, and HMR represents 65–80% of the total lignan content; thus HMR can be obtained in very high quantities and in a convenient way, and large amounts are easily available in a suitable and standardized form, circumventing some limitations which have so far hindered the accomplishment of studies with purified lignans.
The extraction process, described in patent literature, involves Soxhlet extraction of freeze-dried, ground heartwood. HMR extracts were isolated from Norway spruce (Picea abies); freeze-dried ground heartwood was Soxhlet-extracted with hexane to remove non-polar lipophilic extractives. The wood sample was re-extracted with acetone/water (9:1 v/v) to give crude lignans, after which hydroxymatairesinol and its isomer were isolated and re-chromatographed with XAD-resin for further purification.
In the dietary supplement industry, HMR is available primarily as:
- Capsules or tablets containing the standardized HMRlignan™ extract
- Functional food additives incorporated into beverages and food products
- Combination formulas paired with other phytoestrogens or indole-3-carbinol
HMRlignan™ is standardized to contain 80,000 mg/100 g of lignans.
2. Traditional and Historical Use
HMR as a purified, isolated compound has no traditional use — it is a relatively modern scientific discovery arising from wood chemistry research conducted primarily in Finland during the 1970s and 1990s. The pioneering isolation and characterization of Norway spruce lignans, including HMR, is attributed to researcher R. Ekman at Åbo Akademi University, Turku, Finland, working in 1976 and 1979.
Considerable amounts of lignans are also found in coniferous trees; the type of lignans differs in different species and the amounts of lignans vary in different parts of the trees. However, coniferous wood itself has no documented tradition of medicinal dietary use in any specific culture that can be attributed to its lignan content.
The broader class of dietary lignans — found in flaxseed, sesame, rye, and whole grains — has a longstanding association with health through epidemiological research, rather than through a formally documented traditional medicine system. The most common dietary sources of mammalian lignan precursors are unrefined grain products; the highest concentrations in edible plants have been found in flaxseed, followed by unrefined grain products, particularly rye. These foods have centuries of culinary use, though not specifically ascribed to their lignan content in historical medical texts.
HMR itself was first meaningfully characterized as a distinct bioactive compound in 1976 (Ekman), and its biological significance — particularly its role as an enterolactone precursor — was established in peer-reviewed research beginning in 2000 (Saarinen et al., Nutrition and Cancer). Its use as a commercial dietary supplement followed shortly thereafter.
3. Key Constituents, Active Compounds, and Mechanisms of Action
3.1 The HMR–Enterolactone Axis
The most defining biochemical characteristic of HMR is its role as an efficient precursor to the mammalian lignan enterolactone (ENL). The potential for the extraction of the plant lignan hydroxymatairesinol (HMR) in large scale from Norway spruce has given researchers the opportunity to study the metabolism and biological actions of HMR in animals. HMR, the most abundant single component of spruce lignans, was metabolized to enterolactone (ENL) as the major metabolite in rats after oral administration; the amounts of urinary ENL increased with the dose of HMR (from 3 to 50 mg/kg), and only minor amounts of unmetabolized HMR isomers and other lignans were found in urine.
Similar to abundant dietary plant lignans secoisolariciresinol diglycoside (SDG) and matairesinol, HMR is also metabolized into mammalian lignan enterolactone (ENL) in vivo. The conversion pathway proceeds via gut microbial metabolism. Alternative and simultaneous branches of metabolic pathways exist to transform non-absorbed plant lignans into enterolignans; these pathways are mainly defined by bacterial demethylation, reduction, dehydroxylation, and dehydrogenation; nevertheless, the main final metabolites are enterodiol (ED) and enterolactone (EL).
A considerable systemic exposure of HMRlignan was verified by dose-related increases in plasma total (conjugated and unconjugated) concentration of 7-HMR and its metabolites enterolactone, 7-hydroxyenterolactone, and matairesinol. Enterolactone appeared to be the major metabolite. Most (>96%) of the circulating 7-HMR and enterolactone was in conjugated form.
Since enterolactone is produced by specific species of gut microbiota, the capacity to produce it varies between people. Antibiotic treatments can abolish the capacity to produce enterolactone. Diet and gut microbiota conformation and activity are dominant factors affecting the amount and profile of mammalian enterolactones produced in the colon. Great interindividual differences have been observed, which has led to the identification of different phenotypes that can be affected by age and sex, according to the capacity to produce enterolignans.
3.2 Phytoestrogenic / Selective Estrogen Receptor Activity
Lignans are plant polyphenols which may possess anticancer, antioxidant, antimicrobial, anti-inflammatory, and immunomodulatory activities. In particular, the lignan 7-hydroxymatairesinol is a novel precursor of the mammalian lignan enterolactone.
In studies investigating the estrogenicity of HMR and of enterolactone in comparison to estradiol (E2) by measuring effects on growth and apoptotic markers in the human estrogen-sensitive cell line MCF-7, HMR, EL, and E2 concentration-dependently increased the percentage of MCF-7 cells in the S phase of the cell cycle, with the following relative potencies: E2 ≅ EL >> HMR, and efficacies: E2 > HMR >> EL. This indicates that while HMR has measurable estrogenic activity at the cellular level, it is considerably weaker than estradiol.
At high concentrations, HMR has estrogenic properties, which are considerably weaker than those of estradiol. HMR (50 mg/kg body wt) did not exert estrogenic or antiestrogenic activity in the uterine growth test in immature rats, suggesting that at physiologically achievable doses, overt estrogenic uterine effects do not occur in animal models.
Beyond their antioxidant and anti-inflammatory actions at nutritional doses, some lignans regulate the activity of specific nuclear receptors (NRs), such as the estrogen receptors (ERs), and also NRs that are central switches in glucose and fatty acid metabolism such as PPARα, PPARγ, and LXRs, highlighting them as selective nuclear receptor modulators (SNRMs). These include enterodiol and enterolactone, the metabolites produced by the gut microbiota from food lignans.
Increased intake of dietary lignans is also associated with increased serum levels of sex hormone-binding globulin (SHBG) in postmenopausal women. Elevated SHBG can reduce levels of free circulating estrogens and androgens, which has implications for hormone-dependent cancer risk.
3.3 Antioxidant Activity
The antioxidant properties of hydroxymatairesinol were studied in vitro in lipid peroxidation, superoxide and peroxyl radical scavenging, and LDL-oxidation models in comparison with the known synthetic antioxidants Trolox, butylated hydroxyanisol (BHA), and butylated hydroxytoluene (BHT). On a molar basis, HMR was a more effective antioxidant than Trolox in all assays, and more effective than BHT or BHA in lipid peroxidation and superoxide scavenging tests. The in vivo antioxidative effect (evaluated as weight gain of C57BL/6J mice fed an alpha-tocopherol-deficient diet) of HMR (500 mg/kg per day) was comparable to that of DL-alpha-tocopherol (766 mg/kg per day).
3.4 Anti-inflammatory Mechanisms
In cell research, 7-HMR was found to suppress TNF-α-induced inflammatory mediators, such as vascular cell adhesion molecule-1, interleukin-6, and inducible nitric oxide synthase expression both at mRNA and protein levels, and concentration-dependently attenuated reactive oxygen species generation.
7-HMR remarkably induced superoxide dismutase and heme oxygenase-1 expression associated with degradation of Kelch-like ECH-associated protein 1 (KEAP1) and up-regulated nuclear factor erythroid 2-related factor 2 (Nrf2). In addition, 7-HMR time- and concentration-dependently attenuated TNF-α-induced phosphorylation of ERK1/2 and Akt. Moreover, 7-HMR significantly suppressed TNF-α-mediated NF-κB activation by inhibiting phosphorylation and nuclear translocation of NF-κB p65.
These results demonstrated that 7-HMR inhibited TNF-α-stimulated endothelial inflammation, at least in part, through inhibition of NF-κB activation and upregulation of Nrf2–antioxidant response element signaling pathway.
Further mechanistic insights are provided by chemoinformatic analyses. 7-HMR has shown anti-inflammatory effects via inhibition of 5-lipoxygenase, matrix metalloproteinase 2, mitogen-activated kinase p38-alpha, leukotriene B4 receptor, and prostacyclin receptor, and oncoprotective effects through antioxidant activity via inhibition of heme oxygenase-2, inhibition of cyclin-dependent kinases 3 and 4, epidermal growth factor, and mTOR protein.
3.5 Aromatase Inhibition
HMR is metabolized to enterolactone, which inhibits aromatization in vitro. Aromatase is the enzyme that converts androgens to estrogens; its inhibition is one proposed mechanism by which lignans may influence hormone-dependent cancer biology, though this has not been directly confirmed in HMR-specific human clinical trials.
Mammalian lignans have shown the ability to inhibit the conversion of testosterone to 5α-dihydrotestosterone (DHT), the potent intracellular androgen, at concentrations which are achievable in humans. The reduction in DHT concentration would modify the risk of prostate cancer and benign prostatic hyperplasia (BPH).
4. Scientific Evidence by Area of Use
4.1 Cancer Biology — Breast Cancer
Animal and in vitro evidence (preclinical only; no completed human clinical trials specifically for breast cancer):
HMR (15 mg/kg body weight, p.o.) given for 51 days decreased the number of growing tumors and increased the proportion of regressing and stabilized tumors in the rat dimethylbenz[a]anthracene (DMBA)-induced mammary tumor model.
The chemopreventive effects of hydroxymatairesinol, a lignan extracted from Norway spruce, on the development of mammary carcinoma induced by DMBA were studied in rats. HMR administered via diet in an average daily dose of 4.7 mg/kg body weight starting before DMBA induction reduced tumor volume and tumor growth, but no significant reduction in tumor multiplicity (number of tumors/rat) was observed. Anticarcinogenic effects of dietary HMR (4.7 mg/kg) were also evident when administration started after DMBA induction, seen as growth inhibition of established tumors.
Dietary HMR supplementation significantly increased serum and urinary enterolactone and HMR concentrations, but had no significant effect on uterine weight, suggesting that HMR or its major metabolite enterolactone did not have an antiestrogenic effect.
Strength of evidence: Preclinical (animal and cell-based) only. No adequately powered, randomized human clinical trials have been completed specifically testing HMR as a breast cancer preventive or therapeutic agent.
4.2 Cancer Biology — Prostate Cancer
Animal evidence:
Clinical intervention studies and experimental studies with lignan-rich diets suggest that lignans may have inhibitory effects on prostate cancer, but no clinical or experimental studies with purified lignans had been published at the time. The purpose of the landmark study by Bylund et al. (2005) was to investigate the effect of a plant lignan 7-hydroxymatairesinol on LNCaP human prostate cancer xenografts in athymic mice. Athymic nude male mice were injected subcutaneously with LNCaP cells, and starting 3 days after tumor cell injections, a control diet or a control diet supplemented with 0.15% or 0.30% of HMR was administered for 9 weeks.
HMR diet inhibited the growth of LNCaP tumors. Mice treated with HMR had smaller tumor volume, lower tumor take rate, increased proportion of nongrowing tumors, and higher tumor cell apoptotic index compared with controls. Furthermore, the cell proliferation index was reduced in mice receiving the 0.30% HMR diet compared with mice receiving the control diet.
Strength of evidence: Animal model only. No controlled human clinical trials on HMR and prostate cancer have been identified in the peer-reviewed literature.
4.3 Cancer Biology — Hepatoma
The effect of 7-hydroxymatairesinol and its mammalian metabolite, enterolactone, on AH109A hepatoma cell proliferation and invasion in vitro was examined. HMR and ENL inhibited the proliferation and invasion of AH109A hepatoma cells. The 50% inhibitory concentration (IC50) of hepatoma cell proliferation was lower for ENL (10 µM) than HMR (>200 µM); likewise, the IC50 of hepatoma cell invasion was lower for ENL (9 µM) than HMR (144 µM). ENL suppressed hepatoma cell proliferation by accumulating cells in G1 phase and elongating the doubling time of these cells, and by increasing the rate of apoptosis.
Strength of evidence: In vitro and animal data only.
4.4 Cancer Biology — Colorectal/Intestinal
The effects of a lignan, hydroxymatairesinol, and rye bran on intestinal tumor development in adenomatous polyposis coli multiple intestinal neoplasia (Apc)(Min) mice were studied. HMR showed a strong chemopreventive effect in this animal model. HMR resulted in normalization of beta-catenin levels in adenoma tissue, indicating that HMR mediates its chemopreventive effect through the Apc–beta-catenin pathway.
HMR was given in diet at 30 mg/kg per day and decreased the formation of polyps and prevented beta-catenin accumulation into the nucleus, the pathophysiological hallmark of polyp formation in this mouse model.
Strength of evidence: Animal model only. No human clinical trial data available for colorectal applications.
4.5 Menopause and Vasomotor Symptoms
Human clinical evidence (limited):
A single-blind, parallel, pharmacokinetic and dose-comparison study was conducted on 22 postmenopausal females not receiving hormone replacement therapy, enrolled in either a 36 mg/d (low-dose) or 72 mg/d dose (high-dose) regimen. Primary measured outcomes included plasma levels of 7-HMR and enterolactone (ENL), and single-dose pharmacokinetic analysis was performed on a subset of subjects; safety data and adverse event reports were collected as well as data on hot flash frequency and severity.
Pharmacokinetic studies demonstrated 7-HMR Cmax = 757.08 ng/ml at 1 hour and ENL Cmax = 4.8 ng/ml at 24 hours. Results published in the Journal of the American College of Nutrition confirmed that the ingredient was quickly absorbed into the blood and metabolized to enterolactone in healthy postmenopausal women.
In a separate investigation, a supplement containing indole-3-carbinol and 7-hydroxymatairesinol, a dietary ingredient, increased the urinary 2:16-hydroxyestrone ratio, a known biomarker for the reduction of breast cancer risk, in premenopausal women.
Phytoestrogens have been described to help lower total cholesterol and LDL cholesterol and to raise HDL cholesterol. Additionally, increased concentrations of enterolactone have been associated with a decreased risk of cardiovascular disease.
Strength of evidence: The single-blind human study was small (n=22) and not placebo-controlled. It confirmed pharmacokinetics and bioavailability, and collected observational data on hot flash symptoms, but was not designed or adequately powered to establish efficacy for symptom relief. Evidence for HMR specifically reducing menopausal vasomotor symptoms in humans remains preliminary.
4.6 Metabolic Syndrome, Obesity, and Lipid Metabolism
Animal evidence:
7-Hydroxymatairesinol (7-HMR) is a plant lignan abundant in various concentrations in plant foods. A study tested HMRLignan™, a purified form of 7-HMR, and the corresponding Picea abies extract as dietary supplements on a background of a high-fat diet (HFD)-induced metabolic syndrome in mice. Mice 3 weeks old were fed a HFD for 60 days; subgroups were treated with 3 mg/kg body weight 7-HMR or 10 mg/kg body weight total Picea abies extract by oral administration. 7-HMR and the extract limited the increase in body weight (−11% and −13%) and fat mass (−11% and −18%) in HFD-fed mice.
In the 13-week rat toxicity study, plasma triglycerides were dose-dependently depressed in males of all test groups and in females of the mid- and high-dose group, while plasma total cholesterol and phospholipids were decreased in high-dose males. These changes, which have also been reported for other (flaxseed) lignans, were not considered to represent adverse effects.
Strength of evidence: Animal data only. No controlled human trials have established HMR's efficacy for weight management, fat mass reduction, or lipid modification in humans.
4.7 Cardiovascular and Vascular Inflammation
7-Hydroxymatairesinol (HMR) and its major isomer 7-hydroxymatairesinol 2 (HMR2), lariciresinol, secoisolariciresinol, and pinoresinol, isolated from Norway spruce knots, were examined for anti-inflammatory properties in human aortic endothelial cells (Spilioti et al., 2014, Molecular Nutrition & Food Research). This in vitro study demonstrated that both HMR and HMR2 exhibit anti-inflammatory activity in a relevant human cell type.
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.
Strength of evidence: In vitro cell studies and epidemiological associations (with enterolactone, not HMR directly). No randomized controlled trials in humans have been completed specifically with HMR to demonstrate cardiovascular outcomes.
4.8 Neurological — Parkinson's Disease
The gut bacterial metabolite enterolactone, formed through intestinal bacterial metabolism of the lignan 7-hydroxymatairesinol (HMR), was found to attenuate the degeneration of the striatal dopaminergic terminals in Parkinson's disease (PD) in PD rat models. A US patent (US 11,590,101) has also been issued covering use of HMR for alleviating disorders associated with dopaminergic neuron loss.
Strength of evidence: Preclinical animal model data only. No human clinical trials have investigated HMR or enterolactone for Parkinson's disease in a controlled setting.
5. Body Systems and Health Areas Associated with HMR
- Endocrine / Hormonal system: Phytoestrogenic activity mediated primarily through enterolactone; modulation of sex hormone-binding globulin; inhibition of aromatase in vitro.
- Oncology (preclinical): Mammary, prostate, hepatic, and colorectal tumor models in animals; cell-cycle arrest, pro-apoptotic signaling, anti-proliferative effects.
- Cardiovascular system: Anti-inflammatory activity in vascular endothelial cells; lipid-modifying effects in animal models; epidemiological association of enterolactone with cardiovascular health.
- Metabolic system: Attenuation of diet-induced adipogenesis and fat mass accumulation in animal models; modulation of lipid profiles.
- Antioxidant defense: Free radical scavenging; LDL oxidation inhibition; activation of the Nrf2/HO-1 antioxidant response pathway.
- Neurological system (preclinical): Protection of striatal dopaminergic terminals via enterolactone metabolite in animal PD models.
- Gastrointestinal system: Interaction with gut microbiota as a precursor to bioactive enterolignans; normalization of beta-catenin signaling in colorectal adenoma models.
6. Pharmacokinetics and Bioavailability
In short-term toxicity studies, HMR was shown to be well absorbed (>50% of the dose) and rapidly eliminated. In human studies, HMR has been given in single doses up to 1,350 mg to healthy male volunteers without treatment-related adverse events. Rapid absorption from the gastrointestinal tract and partial metabolism to enterolactone in humans was demonstrated.
In the human pharmacokinetic study of postmenopausal women, pharmacokinetic studies demonstrated 7-HMR Cmax = 757.08 ng/ml at 1 hour and ENL Cmax = 4.8 ng/ml at 24 hours, indicating rapid absorption of the parent compound with a delayed appearance of the enterolactone metabolite that is consistent with its formation by colonic bacteria.
As a unique source of lignans, HMRlignan™ is described as a highly bioavailable and efficient precursor of enterolactone. The parent compound undergoes rapid first-pass and systemic metabolism. Most (>96%) of the circulating 7-HMR and enterolactone is in conjugated form. Conjugation (primarily as glucuronide and sulfate conjugates) is typical of polyphenols and influences bioavailability at target tissues.
7. Dosage Forms and Reported Dosages
The following dosages are reported in the cited scientific literature and should not be interpreted as recommendations:
- A single-blind, parallel pharmacokinetic and dose-comparison study in 22 postmenopausal females tested either a 36 mg/d (low-dose) or 72 mg/d dose (high-dose) regimen for 8 weeks.
- In human pharmacokinetic studies, 10 to 30 milligrams of HMRlignan was demonstrated to maintain enterolactone above effective median concentration levels.
- In human studies, HMR has been given in single doses up to 1,350 mg to healthy male volunteers without treatment-related adverse events.
- In rat studies, HMR administered via diet at an average daily dose of 4.7 mg/kg body weight demonstrated chemopreventive effects.
- In mouse metabolic syndrome studies, oral treatment was administered at 3 mg/kg body weight for the purified HMR form or 10 mg/kg body weight for the total Picea abies extract.
- A 13-week rat toxicity study used dietary levels of 0, 0.25, 1, and 4% (w/w) of potassium acetate complex of 7-HMR, which resulted in an average daily intake of 160, 640, and 2,600 mg HMRlignan/kg body weight/day.
- In the prostate cancer xenograft mouse study, a control diet supplemented with 0.15% or 0.30% of HMR was administered for 9 weeks.
8. Safety Considerations and Interactions
8.1 General Toxicity Profile
In short-term toxicity studies (up to 28 days), HMR was essentially non-toxic when given orally to rats and dogs (daily doses up to 2,000 and 665 mg/kg, respectively).
HMRlignan exposure in the 13-week rat study did not significantly affect clinical signs, ophthalmoscopy or neurobehavioural observations, and motor activity.
8.2 Reproductive and Endocrine Effects in Animal Studies
The 13-week rat toxicity study revealed some endocrine-relevant findings at higher doses. The weight of the full and empty caecum showed dose-related increases in males of all treatment groups and in females of the high-dose group. Absolute ovary weights were decreased in all treatment groups, while decreases in relative ovary weights were confined to the mid- and high-dose group. In addition, a marginal lengthening of the estrus cycle was noted in high-dose females.
The relative weight of the kidneys was increased in males of the high-dose group. Apart from prevention of hyaline droplet nephropathy in all high-dose male rats, there were no treatment-related histopathological alterations. The authors concluded that at high doses, HMRlignan showed weak antiestrogenic effects in female rats.
8.3 Estrogenic and Anti-estrogenic Activity — Safety Implications
In human estrogen-sensitive MCF-7 cell studies, HMR, enterolactone, and estradiol (E2) concentration-dependently increased the percentage of MCF-7 cells in the S phase of the cell cycle, with relative potencies: E2 ≅ EL >> HMR, and efficacies: E2 > HMR >> EL. Treatment of MCF-7 cells with either HMR, EL, or E2 also increased the Bcl-2/Bax mRNA ratio. The biological significance of these in vitro findings for humans at typical supplement doses is not established.
8.4 Antibiotic Interactions
Antibiotic treatments can abolish the capacity to produce enterolactone. Since the primary bioactive metabolite of HMR is enterolactone, generated by gut bacteria, any concurrent antibiotic use is expected to significantly reduce the conversion of HMR to enterolactone, potentially diminishing or eliminating its main downstream activity.
8.5 Variability in Metabolic Response
Diet and gut microbiota are dominant factors affecting the amount and profile of mammalian enterolactones produced in the colon. Great interindividual differences have been observed in the context of plant lignan colon metabolism, which has led to the identification of different phenotypes that can be affected by age and sex. This means that bioavailability and biological activity of HMR supplementation will vary substantially between individuals.
8.6 Combination with Other Compounds
Supplementation with a mixture of indole-3-carbinol and HMR lignan in women significantly increased estrogen C-2 hydroxylation, which may constitute a mechanism for the reduction of breast cancer risk as well as risk for other estrogen-related cancers; however, further studies with higher numbers of subjects are indicated.
9. Regulatory and Commercial Status
HMR is primarily commercialized as the proprietary ingredient HMRlignan™ by Linnea SA, Locarno, Switzerland. The invention relating to the use of HMR for the prevention of cancer, non-cancer, hormone-dependent diseases, and cardiovascular diseases by adding it to food or using it as a pharmaceutical preparation has been patented. No specific EFSA, FDA GRAS, or other major regulatory authority approval specific to HMR is documented in the peer-reviewed sources reviewed for this article. HMR has been marketed as a dietary supplement ingredient in North America and Europe.
10. Limitations of the Current Evidence Base
The following critical limitations characterize the HMR evidence base as of the most recent available literature:
- No large-scale randomized controlled trials: The vast majority of evidence for HMR's health effects derives from in vitro cell studies and animal models, not from adequately powered, double-blind, placebo-controlled human clinical trials.
- Small human studies: The one published pharmacokinetic/clinical symptoms study in humans enrolled only 22 subjects, was single-blinded, and lacked a placebo control.
- Metabolic complexity: Because HMR's primary bioactive output is enterolactone, produced by gut bacteria, research must account for the wide interindividual variability in microbial conversion capacity. Most human studies measure enterolactone levels as a proxy rather than testing HMR's effects directly.
- Industry-related research: Several key studies have been conducted with involvement of or support related to Linnea, the commercial manufacturer of HMRlignan™, introducing potential conflicts of interest.
- Extrapolation from other lignans: Many purported health claims for HMR are derived from epidemiological or experimental data about dietary lignans as a class (particularly secoisolariciresinol from flaxseed), and may not be directly applicable to HMR specifically.
References
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