Do Probiotics Reduce TMAO? What the Science Says

November 20, 2025 •

3 min read

Research suggests that elevated levels of the gut metabolite Trimethylamine N-oxide (TMAO) are linked to an increased risk of cardiovascular disease. This has led to intense investigation into potential interventions, including exploring whether probiotics reduce TMAO levels.

Quick Summary

Some probiotics can reduce TMAO levels by changing gut bacteria, but effectiveness is dependent on specific strains and dosage. Research indicates certain Lactobacillus and Bifidobacterium strains are promising, while others show no effect.

Key Points

Strain Specificity is Key: Not all probiotics can reduce TMAO; effectiveness depends on specific bacterial strains, with general supplementation often showing no significant effect.
Proven Strains Exist: Specific strains like Lactobacillus rhamnosus GG and certain Bifidobacterium species have demonstrated TMAO-reducing effects in human and animal studies.
Mechanisms are Varied: Probiotics can lower TMAO by competing with TMA-producing bacteria for resources, degrading TMA directly, or altering overall gut flora composition.
Dietary Changes Complement Probiotics: Modifying your diet to be more plant-based, reducing red meat, and increasing fiber intake can also significantly lower TMAO levels.
More Human Trials are Needed: While preclinical data is promising, larger and more rigorous human studies are required to confirm the optimal probiotic formulations and dosages for reducing TMAO.
Exercise Also Helps: Regular physical activity supports a healthy gut microbiome, which can contribute to lower TMAO levels.

What is TMAO and Why is it a Concern?

Trimethylamine N-oxide (TMAO) is a gut metabolite produced when gut bacteria metabolize nutrients like choline and L-carnitine, which are common in foods like red meat and eggs. This process generates trimethylamine (TMA), which is then converted to TMAO in the liver. High TMAO levels are associated with increased risk of cardiovascular events, including heart attack and stroke, by contributing to inflammation and affecting platelet function.

The Role of the Gut Microbiome in TMAO Production

The composition of the gut microbiome significantly influences TMAO production. Certain bacteria containing the enzyme choline TMA-lyase are key to producing TMA. Modulating the gut microbial community is a promising way to potentially lower TMAO levels. This has led to research into using probiotics to alter the gut flora and reduce TMAO.

How Probiotics Influence TMAO Levels: Mechanisms and Studies

Probiotics can potentially influence TMAO levels through several mechanisms, including competing with TMA-producing bacteria for substrates, directly metabolizing TMA, or altering the overall gut microbiome composition. However, studies on the effectiveness of probiotics for reducing TMAO have been inconsistent, highlighting that the impact is highly dependent on the specific strain used.

Specific Probiotic Strains That Show Promise

Several probiotic strains have shown potential in reducing TMAO levels in studies:

Lactobacillus rhamnosus GG (LGG): Identified as one of the more effective strains in reducing TMAO in both human and animal models.
Bifidobacterium species: Supplementation with certain Bifidobacterium species, such as B. animalis subsp. lactis F1-3-2 and Bifidobacterium longum, has reduced circulating TMAO levels in some studies.
Lactobacillus plantarum strains: Strains like ZDY04 and LP1145 have shown promise in animal models.
Enterobacter aerogenes ZDY01: Another strain that demonstrated a positive effect on TMAO in animal studies.
Bilophila wadsworthia: Linked to reduced genetic susceptibility to TMAO in some studies.

Comparative Effects of Probiotic Strains on TMAO


Strain/Formulation	Study Type	Effect on TMAO Levels	Notes
Lactobacillus rhamnosus GG	Human & Animal Trials	Reduced	Found to be among the most effective strains.
Lactobacillus plantarum GLP3	Human Trial	Reduced	Significant reduction noted in high-risk CVD patients.
Bifidobacterium (mixed species)	Human Trial	Reduced	Intervention with Bifidobacterium capsules showed reduction.
Bifidobacterium animalis subsp. lactis F1-3-2	Animal Study	Reduced	Showed prominent performance in mouse models.
Lactobacillus amylovorus LAM 1345	Animal Study	Reduced	Effective when used alone or in multi-strain formulas.
VSL#3 (multi-strain)	Human Trial	No significant effect	One multi-strain formulation showed no impact on TMAO levels.
Lactobacillus casei Shirota	Human Trial	No significant effect	No significant effect observed in atherosclerotic patients.

Conclusion

Research suggests that certain probiotic strains can help reduce TMAO levels by influencing the gut microbiome. However, not all probiotics are effective, and the impact is highly strain-specific. While promising results have been seen with strains like Lactobacillus rhamnosus GG and specific Bifidobacterium species, more extensive human trials are needed to confirm optimal use. Alongside probiotics, dietary changes, exercise, and focusing on overall gut health are important strategies for managing TMAO-related risks.

What are the other strategies to lower TMAO?

Evidence-based strategies to naturally lower TMAO include:

Dietary modification: Reducing intake of red meat and eggs while increasing fiber from plant-based foods can lower TMAO precursors.
Increasing fiber: Soluble fiber supports a beneficial gut microbiome composition.
Polyphenol intake: Compounds like resveratrol and quercetin may help reduce TMAO.
Regular exercise: Physical activity can positively impact the gut microbiota and cardiovascular health.

Visit this resource for more information on the impact of diet and gut microbes on cardiovascular health.

Frequently Asked Questions

TMAO is a compound produced after gut bacteria digest certain nutrients, and high levels are linked to an increased risk of cardiovascular disease, including atherosclerosis and heart attack.

No, research indicates that the effect of probiotics on TMAO is strain-specific. Many general probiotic supplements have not been shown to lower TMAO, so it's important to choose specific, proven strains.

Promising strains identified in research include Lactobacillus rhamnosus GG, Lactobacillus plantarum GLP3, and certain species of Bifidobacterium, such as B. animalis subsp. lactis.

Probiotics can reduce TMAO by altering the gut microbiome. They may competitively inhibit TMA-producing bacteria, directly consume TMA, or foster a microbial environment that is less conducive to TMAO production.

Reducing the intake of red meat, eggs, and high-fat dairy, which are rich in TMAO precursors, is effective. Adopting a plant-based diet and increasing fiber intake can also promote beneficial gut bacteria.

Yes, some nutraceuticals like resveratrol, quercetin, and soluble fiber have shown potential in reducing TMAO levels.

Probiotics are generally safe, but results are not guaranteed. It is best to combine them with proven lifestyle interventions and consult a healthcare provider, especially if you have cardiovascular risk factors.