Probiotics have not been shown to reliably lower TMAO in people, and current evidence does not establish a supplement that does. A meta-analysis of eight randomized trials found no significant overall reduction. The studies measured TMAO, a biomarker; they did not show that changing it with a supplement prevents heart disease or improves other clinical outcomes.
What human studies say about probiotics
The strongest pooled evidence is a 2022 meta-analysis of eight randomized controlled trials involving 270 adults. Probiotics produced a weighted mean difference in TMAO of −0.08 μmol/L compared with control (95% confidence interval −0.76 to 0.60; P=0.813), which was not statistically significant. The authors also found no significant effect in healthy or unhealthy participant subgroups. An analysis suggesting a greater reduction among participants younger than 50 is exploratory and does not change the overall result. Read the meta-analysis.
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Individual trials were small and product-specific
- In a 2021 trial, 40 healthy men aged 20–25 took a daily multi-strain probiotic or control for four weeks and underwent a phosphatidylcholine challenge. The probiotic changed some microbiome measures but did not significantly reduce the rise in serum TMAO after the challenge. Trial details.
- In a 2015 trial, 19 healthy, non-obese men aged 18–30 followed a high-fat, hypercaloric diet for four weeks. VSL#3 did not significantly change the increase in plasma TMAO compared with placebo. The small, narrowly defined sample limits how widely the result can be applied. Trial details.
These studies do not prove that every probiotic formulation has no effect in every population. They do show that a dependable general benefit has not been established, and they are not a basis for recommending a brand, strain, or dose to lower TMAO.
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There is no established supplement choice for this purpose. A 2019 systematic review identified 13 controlled studies of dietary supplements and pharmacological agents, but the products and study methods varied enough that the results could not be reliably synthesized. The authors concluded that the evidence was inconsistent. Read the review.
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- Support Your Gut: Our probiotic contains 10 diverse high-quality probiotic strains and organic prebiotics - synergistically working together to support your gut health. Expertly crafted to support occasional constipation, diarrhea, gas & bloating!
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Choline and L-carnitine are nutrients discussed in the TMAO pathway, not proven TMAO-lowering remedies. One randomized trial compared choline supplements with eggs in participants with normal kidney function, illustrating why different sources and interventions should not be treated as interchangeable. It does not establish a general supplement strategy for reducing TMAO. See the choline trial.
Why a plausible gut-microbe mechanism is not enough
Probiotics and synbiotics are studied partly because changing gut microbes might alter the microbial metabolites they produce. That mechanism is plausible, but it is not proof that a product will lower TMAO in people. In the pooled trials, probiotics had no significant overall effect; in one challenge study, changes in some microbiome measures did not translate into a significant reduction in the TMAO response. A broader review of microbiota-driven interventions also covers the complexity of this research. Read the review.
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What to consider before taking a probiotic
Do not choose a product based on a claim that it lowers TMAO: that benefit has not been established. If you are considering a probiotic for another reason, assess the specific product and its evidence rather than relying on a high CFU count or a multi-strain label. NCCIH notes that “Different types of probiotics may have different effects,” so results for one strain do not establish benefits for others. Useful label details include:
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- the exact genus, species, and strain;
- the health indication for which the product is being considered and whether evidence supports it;
- the use-by date and any storage requirements; and
- whether a clinician or dietitian recommends it for your circumstances.
Many probiotics are sold as dietary supplements and do not require FDA approval before marketing. A product’s availability or marketing is not proof of a TMAO benefit. NCCIH explains probiotic uses and safety.
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Probiotic safety and who needs extra caution
Probiotics have a history of use, particularly among healthy people, but detailed safety information is limited. Harmful effects are more concerning for people who are severely ill or have compromised immune systems. NCCIH notes that “The risk of harmful effects from probiotics is greater in people with severe illnesses or compromised immune systems”; infections have been reported, including severe infections in premature infants. If you have a significant medical condition, ask a qualified health professional before using a probiotic supplement. NCCIH’s probiotic safety overview.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What the TMAO results can—and cannot—tell you
The cited intervention studies evaluated TMAO measurements, not whether supplement-induced changes reduce cardiovascular events or improve health. They therefore do not establish TMAO as a treatment target or prove that lowering the biomarker with a supplement benefits patients. Do not start, stop, or replace prescribed treatment based on a TMAO-related supplement claim.
Quick Recap
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- Support Your Gut: Our probiotic contains 10 diverse high-quality probiotic strains and organic prebiotics - synergistically working together to support your gut health. Expertly crafted to support occasional constipation, diarrhea, gas & bloating!
- Survives the Gut: From start to finish - this probiotic is designed to survive the gut & maximize the colonization of our strains. We use a shelf-stable bottle, acid-resistant capsules, and 60 Billion Colony forming units (CFU) to achieve this!
- Backed By Science - Our probiotics are crafted based on scientific research. We have partnered with a network of expert physicians to help review our products & research. We strive to educate & help you with informed decisions regarding your health.
- Safety Assured Standard of Quality: Our 60B probiotic is 3rd-party tested for purity and potency. Each bottle is manufactured with love & care in the USA with strict quality control - using imported and domestic ingredients.
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