Probiotic SDG Metabolism

The primary reason for taking lignans is that they are eventually converted into the enterolignans called enterodiol (ED) and enterolactone (EL). ED and EL, along with melatonin, were the substances studied in the leading paper on the successful treatment of Cushings disease in dogs (Fecteau 2011). Other research in humans and animals have shown these enterolignans to have anti-oxidant effects and estrogen replacement modulation effects, as well as “anti-cancer, antioxidant, antimicrobial, anti-inflamatory, and immunomodulating effects”. (Cosentino, 2007).

Getting from raw flax to the desired enterolignans is a multi-step process. The first step in the process is mechanical. Research shows that crushing and milling flaxseeds is key to obtaining the maximum amount of secoisolariciresinol disglucoside (SDG), the key ingredient in our flax-based lignan products, from the flax seeds. (Kuijsten, 2005).

The SDG then undergoes a series of microbiological steps once it is in the human gut. Each of those steps is carried out, not by the human or animal body, but by bacteria found in the gut. (Estimates vary on the exact ratio, but they all agree that there are more bacteria and other non-human cells than human cells in all of us! These steps take place mostly in the proximal (first and middle parts of the) colon and consist of:

  1. Conversion of SDG into secoisolariciresinol (SECO) (the removal of sugar molecules, called deglycosylation). This step can be carried out by many bacteria commonly found in a healthy gut (especially that of the Bacteroides and Cloistridium species). However, Clostridium saccharogumia has been shown to be especially effective at this conversion.
  2. Conversion of SECO into an intermediate molecule by removal of one of more methyl groups (CH3). This may be accomplished by any of several species of bacteria commonly found in a healthy gut, including Ruminococcus productus, Eubacterium limosum and Blautia producta. (There is some controversy about the order of steps 2 and 3–whether demethylation occurs before dehydroxylation or vice versa. (Wang, 2000 at 1609.))
  3. The intermediate molecule is then transformed into ED by the removal of one or more hydroxy groups (dehydroxylation). This is usually accomplished in the lab by a combination of bacteria (B. producta and Eggerthella lenta).
  4. To produce EL (the other enterolignan), some of the ED is dehydrogenated. This step is carried out by Lactonifactor longoviformis. So far, this is the only known bacteria strain capable of carrying out this final step.

(Woting et al, 2010, 507.) Thus, gut microbes are absolutely critical to the production of EN and EL. In fact, there would be no EN or EL production at all without those microbes. Accordingly, getting the right mix and quantity of gut microbes should improve the effectiveness of any lignans-based therapy.

The more SDG by-products that are produced at each stage, the more ED and EL that will ultimately be produced. (Clavel, 2005 at 6080, 6082.) Accordingly, probiotics that promote the bacteria used in each stage should maximize total ED and EL production.

Although less research has been done with HMR and some of the other lignans, all of them require metabolism by microbes in a process similar to that described above for flax-based lignans. (Note that HMR is not a precursor to ED but only for the EL enterolignan.)

In addition, even healthy humans and animals will benefit from a healthy microbiome. Prebiotics, which are essentially food for the probiotics and other microbes, and probiotics (good bacteria) have been shown to . . .


Step 1:
Cloistridium (especially, C. saccharogumia and C. scindens)

Step 2:
Ruminococcus productus
Eubacterium limosum

Steps 2 and 3:
Blautia producta

Step 3:
Eggerthella lenta

Step 4:
Lactonifactor longoviformis

**L. salivarius and L. gasseri have both been shown to produce both ED and EL from SDG extract. [These should be incorporated into any probiotic that targets ED and EL production, and they are available from Scientific Living.] (Bravo, 2017)

***B. adolescentis has been shown to produce ED from lignan extracts. (Gaya, 2017.) However, I do not believe this is available commercially. Check the final list of probiotics against Table 1 to at least confirm SECO production.

++Pierotina, 2019 found Bifidobacterium bifidum INIA P466, Bifidobacterium catenulatum INIA P732 and Bifidobacterium pseudolongum INIA P2) were found capable of producing low levels of enterodiol (2–11 μM) from lignan extracts; while another one (Bifidobacterium pseudocatenulatum INIA P946) was found to produce an important increment of the lignan secoisolariciresinol (SECO). And that Lactobacillus gasseri INIA P508, Lactobacillus salivarius INIA P448 and Lb. salivarius INIA P183 yielded both ED and EL from SECO, while they did not metabolise matairesinol. B. catenulatum INIA P732 and Lb. gasseri INIA P508 were the strains that transformed the greatest percentage of SECO. Data from 20+ strains of bacteria are listed in tables 3 and 4 of this article. Here’s a full version of it:


L. casei
L. plantarum
L. salivarius*
L. gasseri*
Bifidobacterium bifidum*
B. animalis

* These are essential components. Other components can be swapped if there are any that have been identified to promote any of the following:

Cloistridium (especially, C. saccharogumia and C. scindens)
Ruminococcus productus
Eubacterium limosum
Blautia producta
Eggerthella lenta
Lactonifactor longoviformis

Or if any of these are commercially available:

Bifidobacterium adolescentis
Bifidobacterium catenulatum
Bifidobacterium pseudolongum


Kuijsten, Arts, van’t Veer and Hollman, The Relative Bioavailability of Enterolignans in Humans Is Enhanced by Milling and Crushing of Flaxseed, J. Nutr. 135: 2812-2816 (2005).

Woting, Clavel, Loh and Blaut, Bacterial Transformation of Dietary Lignans in Gnotobiotic Rats, FEMS Microbiol Ecol 72 (2010).

Wang, Meselhy, Li, Qin, Hattori, Human Intestinal Bacteria Capable of Transforming Seciosolariciresinol Diglucoside to Mammalian Lignans, Enterodiol and Enterolactone, Chem. Pharm. Bull. 48(11), 1609 (2000).

Clavel, Henderson, Alpert, Phillippe, Ritgottier-Gois, Dore and Blaut, Intestinal Bacterial Communities That Produce Active Estrogen-Like Compounds Enterodiol and Enterolactone in Humans, Appl. Environ. Microbiol., 71 (2005).

Clavel, T., Doré, J., & Blaut, M. (2006). Bioavailability of lignans in human subjects. Nutrition Research Reviews, 19(2), 187-196. doi:10.1017/S0954422407249704

Bravo, D., Peirotén, A., Álvarez, I., Landete, J., Phytoestrogen metabolism by lactic acid bacteria: Enterolignan production by Lactobacillus salivarius and Lactobacillus gasseri strains Journal of Functional Foods 37 (2017) 373-378.

Gaya, P., Peirotén, A., Medina, M., Landete, J., Bifidobacterium adolescentis INIA P784: The first probiotic bacterium capable of producing enterodiol from lignan extracts, Journal of Functional Foods 29 (2017) 269-74.

Peiroténa, A., Gayaa, P., Álvarezb, I., Bravoa, D., Landetea, J., Influence of different lignan compounds on enterolignan production by Bifidobacterium and Lactobacillus strains, Int. J. Food Microbiology 289 (2019) 17-23.


EL may be more effective than ED in fighting ovarian cancer. Liu H, Liu J, Wang S, et al. Enterolactone has stronger effects than enterodiol on ovarian cancer. J Ovarian Res. 2017;10(1):49. Published 2017 Jul 24. doi:10.1186/s13048-017-0346-z

Clavel, 2006: Besides SDG, R. productus also catalyzes O-demethylation in lariciresinol (from sesame seeds), matairesinol (HMR, oil seeds, many plants) and pinoresinol (sesame seeds, olive oil, other plants). E. lenta also catalyzes the reduction of pinoresinol to lariciresinol and from lariciresinol to SECO. Organisms involved in the production of ED occurred at a mean cell density of 6 x 10^8 cells/g faeces while those involved in the production of EL occurred at 3 x 10^5 cells/g. “Women tend to harbor more enterolignan-producing bacteria than men.” Progesterone may be a factor in this as it lengthens transit time in the gut, and transit time is correlated with increased enterolignan production. Early work indicates that some metabolism of lignans may happen in the liver via enteropathic circulation. If this is so, then additional liver support may be indicated. Figure 1 of this article is a fantastic diagram of the metabolism of the major lignans and the steps and bacteria involved in each step.

Clavel, 2005: “Significantly larger amounts of EL were produced . . . from individuals with moderate to high concentrations of EL-producing behavior.” Two organisms that demethylate and dehydroxylate SECO are Peptostreptococcus productus and Eggerthella lenta. Women tend to have higher concentrations of ED and EL producing organisms than men.

A comparison of Stumpf, et al. (2000) to Tarpila et al. (2002) indicates that the prebiotic inulin may raise the maximum concentration of enterolignans in blood levels. Stumpf found a plateau effect after week 6 of lignan-based dietary intervention, while Tarpila found continuous increases in concentrations over its 4-month study period. A potentially significant factor distinguishing the studies was the addition of inulin to the Tarpila dietary intervention. Katariina Stumpf, Pirjo Pietinen, Pekka Puska and Herman Adlercreutz, Changes in Serum Enterolactone, Genistein, and Daidzein in a Dietary Intervention Study in Finland, Cancer Epidemiol Biomarkers Prev December 1 2000 (9) (12) 1369-1372. Tarpila S, Aro A, Salminen I, Tarpila A, Kleemola P, Akkila J & Adlercreutz H (2002) The effect of flaxseed supplementation in processed foods on serum fatty acids and enterolactone. European Journal of Clinical Nutrition 56, 157–165.

Lignans should be taken only under medical supervision in infants, children and pregnant or lactating women. Ward WE, Jiang FO & Thompson LU (2000) Exposure to flaxseed or purified lignan during lactation influences rat mammary gland structures. Nutrition and Cancer 37, 187–192.

Peiroténa, 2019: “three bifidobacteria strains (Bifidobacterium bifidum INIA P466, Bifidobacterium catenulatum INIA P732 and Bifidobacterium pseudolongum INIA P2) were found capable of producing low levels of enterodiol (2–11 μM) from lignan extracts; while another one (Bifidobacterium pseudocatenulatum INIA P946) was found to produce an important increment of the lignan secoisolariciresinol (SECO). Subsequently, the three enterodiol-producing bifidobacteria and another three Lactobacillus strains previously identified as enterolignans producers (Lactobacillus gasseri INIA P508, Lactobacillus salivarius INIA P448 and Lb. salivarius INIA P183), were tested on pure lignans yielding both en-
terodiol and enterolactone from secoisolariciresinol (SECO), while they did not metabolised the other lignan tested (i.e. matairesinol). B. catenulatum INIA P732 and Lb. gasseri INIA P508 were the strains that transformed the greatest percentage of SECO, yielding enterolactone concentrations above 2 mM.” See especially Tables 3 and 4, which quantitatively show metabolic effects of many Bifidobacteria and Lactobacilli. Significantly, no metabolism of MAT either into EL or from SECO was observed in any of the tested strains. There is some indication that something in SDG extract (vs pure SECO) impairs the growth of Bifidobacteria, as the SDG extract produced less ED and no EL (as compared with the pure SECO). The pure SECO formulation produced much more EL than ED. Some studies indicate that increases in deglycosylation of SDG int SECO do NOT influence ED and EL production while others have shown such an influence. Perhaps the difference is that pure SDG was used in the former and flax extracts rich in SDG were used in the latter. [KG: Need to compare the Quartieri, 2016 and Gaya, 2016b studies.]

Wang, 2000: An early paper on the metabolism of SDG.