Flaxseed and gut bacteria in lab tests
What it found
In lab tests with human gut bacteria, both whole flaxseed and defatted flaxseed press cake changed the mix of bacteria and boosted compounds called short-chain fatty acids.
The two forms had similar effects.
What they found
Animal and lab studies
Bacteria mix changed
Both flaxseed forms lowered the variety of gut bacteria and shifted the dominant groups to Firmicutes, Proteobacteria, and Bacteroidetes. The two forms had almost identical effects.
Short-chain fatty acids
Levels of acetic, butyric, and propionic acids rose over 24 hours, with acetic acid the most abundant. Lactic acid went up in the first 6 hours then fell.
Lignan conversion
The gut bacteria quickly broke down flaxseed lignans into secoisolariciresinol, enterodiol, and enterolactone. Press cake produced higher amounts of enterodiol and enterolactone than whole flaxseed.
Bile acids
The bile acids added to the cultures were used up and converted into secondary bile acids 7-ketolithocholic acid and α-muricholic acid.
Cyclolinopeptides
During fermentation, some oxidized cyclolinopeptides decreased while non-oxidized forms increased, showing the fermentation mix could reduce these compounds.
What the authors conclude
“However, more in vivo studies are needed to ascertain the dysbiotic effect of flaxseed supplementation seen here to see if they pose any dangers to either healthy individuals or people with circulatory diseases.”
Also in their conclusions
- They conclude that press cake and whole flaxseed are equivalent in how they change gut bacteria and how they work.
- They say press cake may be better as a food additive because it resists oxidation and could be more acceptable to consumers.
- They call for more studies in living animals or people to check if the bacterial changes seen here could be harmful.
How it was done
The authors wanted to see how flaxseed fibers are fermented by gut bacteria, because little research has been done on this.
They used a lab model that mimics the human gut, mixing digested whole flaxseed or defatted flaxseed press cake with gut bacteria from three healthy adults. They measured changes in bacteria and compounds over 24 hours.
What it can’t tell you
- This was a lab test with gut bacteria outside the body, so it cannot show what happens in people.
- The model used bacteria from only three donors and ran for just 24 hours, so it may not reflect long-term effects in a real gut.
Who paid
- Funding
- Funded by University of Applied Sciences and Arts Western Switzerland, P1- HealthFood program (from the PubMed record).
- Conflicts
- The authors declare no conflict of interest.
- Authors work at
- Technical University of Munich, Germany; HES-SO University of Applied Sciences and Arts Western Switzerland Valais-Wallis, Switzerland; HES-SO University of Applied Sciences and Arts Western Switzerland, Switzerland
The paper
- Title
- Dietary Modulation of the Human Gut Microbiota and Metabolome with Flaxseed Preparations
- Type
- Study
- Evidence
- Animals and lab studies
- Summarised from
- Full text
- Cite
- Kleigrewe K, Haack M, Baudin M, et al (2022). Dietary Modulation of the Human Gut Microbiota and Metabolome with Flaxseed Preparations. International journal of molecular sciences. doi:10.3390/ijms231810473Free full textPubMed 36142393DOI
Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error