Marker Guide

Trimethylamine (TMA) producing microbes

What this marker measures

The collective capacity of the microbial community to produce trimethylamine (TMA) from dietary precursors such as choline and carnitine. TMA is absorbed and converted in the liver to TMAO, which at higher circulating levels has been associated with inflammatory pathways and cardiovascular risk^1–6.

Clinical associations

Consider this marker when your patient presents with:

Cardiovascular risk

Atherosclerosis risk, cardiovascular disease, dyslipidaemia, or inflammatory markers where TMAO-related pathways may contribute

Dietary context

High red meat intake or use of free choline/carnitine supplements where microbial TMA production may be relevant.

Metabolic-inflammatory presentations

Insulin resistance, type 2 diabetes, obesity, NAFLD/MASLD, metabolic syndrome or chronic low-grade inflammation where gut-derived metabolites may be relevant

Renal concerns

Chronic kidney disease or reduced renal function, where circulating TMAO may be elevated due to reduced excretion capacity

Interpreting the result

All results are compared to Microba's healthy cohort to determine whether they fall within or outside the expected range.

LOW

TMA-producing potential is lower than expected

This suggests lower TMA-producing potential. No marker-specific intervention needed.

Within Range

TMA-producing potential is within expected parameters

This does not suggest elevated microbial TMA-producing potential.

HIGH

TMA-producing potential is higher than expected

Mayindicateincreasedpotentialto produce TMA, which can be converted to TMAO in the liver. Interpret alongside diet, renal function,andcardiovascular risk. Action: see patient management insights below.

Patient management insights

Reduce microbial TMA production and limit TMAO-driven inflammation.

Dietary strategies

Limiting dietary carnitine intake (from red meat) may reduce plasma trimethylamine N-oxide (TMAO)^7–10.
GRACE C
‍
Carnitine supplementation may increase plasma TMAO. When aiming to reduce plasma TMAO, limiting or avoiding carnitine supplementation may be effective^11–13.
GRADE C

Limiting or avoiding free choline supplementation may reduce plasma trimethylamine N-oxide (TMAO)^14–16.
GRACE C
‍
Cruciferous vegetables may reduce urinary trimethylamine N-oxide (TMAO)¹⁷GRADE D

Supplementation

Grape pomace extract may reduce plasma trimethylamine N-oxide (TMAO)^18,19.
GRADE D

Reducing plasma homocysteine may reduce plasma trimethylamine N-oxide (TMAO)²⁰.
GRADE D

Other clinical strategies

Reducing plasma homocysteine may reduce plasma trimethylamine N-oxide (TMAO)²⁰.
GRADE D

Tips for patients discussion

Your report shows elevated microbial capacity to produce TMA, a compound your liver can convert to TMAO. Higher TMAO has been linked with cardiovascular risk. Red meat is the main dietary contributor, so reducing red meat and increasing fibre-rich plant  foods may help.

The community

TMA is not produced by a single species, it’s a community-level function. Here are some of the most commonly-detected contributors, however this list is not exhaustive.

Acetatifactor sp900066565
Agathobacter faecis
Agathobacter rectale
Agathobaculum butyriciproducens
Anaerostipes hadrus
Clostridium_M sp000431375
Clostridium_Q sp003024715
Coprococcus_A catus
Coprococcus_B comes
Eubacterium_E hallii
Eubacterium_I ramulus
Faecalibacterium MIC7145
Faecalibacterium prausnitzii_C
Faecalibacterium prausnitzii_D
Faecalibacterium prausnitzii_G
Faecalibacterium prausnitzii_I
Gemmiger formicilis
Gemmiger MIC9530
Gemmiger sp003476825
Lawsonibacter asaccharolyticus
Odoribacter splanchnicus
Roseburia hominis
Oscillibacter sp900066435
Roseburia inulinivorans

How results are calculated

All microbiome marker results are compared against the Microba Healthy Cohort — a purpose-built reference group of more than 450 healthy individuals, collected and analysed using the same workflow as patient samples.

Each marker is scored by comparing the patient's relative abundance against the cohort average. The distance from this average is expressed as standard deviations, and determines whether a result is classified as Low, Borderline, or High.

How the result scale works

▲ AVG (Healthy Cohort average)

The patient's relative abundance is compared to the Healthy Cohort average. A negative distance from average means the microbial group is less abundant than the Healthy Cohort. A positive distance means it is more abundant. Results falling outside the expected range are classified as borderline or high/low (borderline high/low:+/-0.68,andhigh/low:+/-1.28).

Evidence grading for patient management insights

The letter grades shown next to each patient management insight show the quality of the research behind it. Every insight provided has been through a rigorous review of the scientific literature and graded using the NHMRC Levels of Evidence, so you can see exactly how strong the evidence is before applying it in practice.

Source references for all clinical associations, interpretation definitions, and patient management insights on this card.

1. Chen, S. et al. Correlation between serum trimethylamine-N-oxide and body fat distribution in middle-aged and older adults: a prospective cohort study. Nutr J 23, 70 (2024).
2. Jalandra, R., Makharia, G. K., Sharma, M. & Kumar, A. Inflammatory and deleterious role of gut microbiota-derived trimethylamine on colon cells. Front. Immunol. 13, 1101429 (2023).
3. Farhangi, M. A. & Vajdi, M. Novel findings of the association between gut microbiota–derived metabolite trimethylamine N-oxide and inflammation: results from a systematic review and dose-response meta-analysis. Critical Reviews in Food Science and Nutrition 60, 2801–2823 (2020).
4. Gencer, B. et al. Gut Microbiota‐Dependent Trimethylamine N‐oxide and Cardiovascular Outcomes in Patients With Prior Myocardial Infarction: A Nested Case Control Study From the PEGASUS‐TIMI 54 Trial. JAHA 9, e015331 (2020).
5. Chou, R.-H. et al. Trimethylamine N-Oxide, Circulating Endothelial Progenitor Cells, and Endothelial Function in Patients with Stable Angina. Sci Rep 9, 4249 (2019).
6. Senthong, V. et al. Intestinal Microbiota‐Generated Metabolite Trimethylamine‐ N‐ Oxide and 5‐Year Mortality Risk in Stable Coronary Artery Disease: The Contributory Role of Intestinal Microbiota in a COURAGE‐Like Patient Cohort. JAHA 5, e002816 (2016).
7. Tate, B. N. et al. Changes in Choline Metabolites and Ceramides in Response to a DASH-Style Diet in Older Adults. Nutrients 15, 3687 (2023).
8. Krishnan, S. et al. Adopting a Mediterranean-style eating pattern with low, but not moderate, unprocessed, lean red meat intake reduces fasting serum trimethylamine N-oxide (TMAO) in adults who are overweight or obese. British Journal of Nutrition 128, 1738–1746 (2022).
9. Crimarco, A. et al. A randomized crossover trial on the effect of plant-based compared with animal-based meat on trimethylamine-N-oxide and cardiovascular disease risk factors in generally healthy adults: Study With Appetizing Plantfood—Meat Eating Alternative Trial (SWAP-MEAT). The American Journal of Clinical Nutrition 112, 1188–1199 (2020)
.10. Wang, Z. et al. Impact of chronic dietary red meat, white meat, or non-meat protein on trimethylamine N-oxide metabolism and renal excretion in healthy men and women. European Heart Journal 40, 583–594 (2019).
11. Sawicka, A. K., Renzi, G. & Olek, R. A. The bright and the dark sides of L-carnitine supplementation: a systematic review. J Int Soc Sports Nutr 17, 49 (2020).
12. Bordoni, L. et al. A Pilot Study on the Effects of l-Carnitine and Trimethylamine-N-Oxide on Platelet Mitochondrial DNA Methylation and CVD Biomarkers in Aged Women. Int J Mol Sci 21, 1047 (2020).
13. Samulak, J. J. et al. L-Carnitine Supplementation Increases Trimethylamine-N-Oxide but not Markers of Atherosclerosis in Healthy Aged Women. Ann Nutr Metab 74, 11–17 (2019)
.14. Wilcox, J. et al. Dietary Choline Supplements, but Not Eggs, Raise Fasting TMAO Levels in Participants with Normal Renal Function: A Randomized Clinical Trial. The American Journal of Medicine 134, 1160-1169.e3 (2021)
.15. Taesuwan, S. et al. Choline metabolome response to prenatal choline supplementation across pregnancy: A randomized controlled trial. FASEB J 35, e22063 (2021).
16. Cho, C. E. et al. Effect of Choline Forms and Gut Microbiota Composition on Trimethylamine-N-Oxide Response in Healthy Men. Nutrients 12, 2220 (2020).
17. Cashman, J. R. et al. In vitro and in vivo inhibition of human flavin-containing monooxygenase form 3 (FMO3) in the presence of dietary indoles. Biochemical Pharmacology 58, 1047–1055 (1999).
18. Annunziata, G. et al. Effect of Grape Pomace Polyphenols With or Without Pectin on TMAO Serum Levels Assessed by LC/MS-Based Assay: A Preliminary Clinical Study on Overweight/Obese Subjects. Front. Pharmacol. 10, (2019).
19. Annunziata, G. et al. Effects of Grape Pomace Polyphenolic Extract (Taurisolo®) in Reducing TMAO Serum Levels in Humans: Preliminary Results from a Randomized, Placebo-Controlled, Cross-Over Study. Nutrients 11, 139 (2019).
20. Obeid, R. et al. Plasma trimethylamine-N-oxide following supplementation with vitamin D or D plus B vitamins. Molecular Nutrition & Food Research 61, 1600358 (2017).