M TMAO 1125x1125

Choline, Eggs and TMAO:

Recent Study Offers Important New Insight

Jen Houchins, PhD & Mickey Rubin, PhD

May 17, 2021

Cardiometabolic Health

Nutrients in Eggs

Scientists have no shortage of ways to measure a person’s cardiovascular disease risk. You are likely very familiar with low-density lipoprotein cholesterol (LDL-C), blood pressure, or markers of inflammation like c-reactive protein, just to name a few. In recent years you may have also heard of another potential risk factor for cardiovascular disease: trimethylamine-N-oxide (TMAO).

TMAO can form after eating foods that contain choline, an important nutrient for brain health found in egg yolk, fish, poultry, and red meat. It can be measured in the blood but is actually produced in the gut. TMAO has been linked with atherosclerosis in animal studies, while observational studies in humans have shown that those with higher blood levels of TMAO have higher cardiovascular disease risk.1  The foods you eat may impact the amount of TMAO precursors and potentially the gut microbial composition, which in turn, could impact the development of TMAO.2  A lingering question has been to what extent is TMAO impacted by diet –  is TMAO just an indicator or are underlying disruptions in metabolism leading to the relationship with atherosclerosis?3,4

Ten years ago, researchers at The Cleveland Clinic published one of the first studies proposing a link between TMAO, dietary choline, and cardiovascular disease risk,5 but have just published a new study that offers some important new information about choline from eggs, one of the best food sources of choline available. The new study published in The American Journal of Medicine explored the difference between consuming eggs, a whole food source of choline, and taking supplemental choline on TMAO production, and concluded “… it may be more prudent to recommend natural sources of choline, like eggs, over supplements.”6

In this study of healthy adults, TMAO concentrations increased from baseline to end-of-study in the participants who consumed a choline bitartrate supplement alone or in combination with whole eggs or egg whites; however, there was no change in TMAO concentrations in the participants who consumed eggs alone or for those who took supplement of phosphatidylcholine, a form of choline found in eggs.

The results of this new study from Cleveland Clinic align with other studies in healthy, young adults that have indicated higher intake of choline from eggs (2-3 eggs/day) has no impact on blood levels of TMAO.7-9  Additionally, a recent study in postmenopausal women who were overweight found that consuming two eggs per day for four weeks did not impact TMAO concentration.10  Overall, “Most recent dietary interventions do not support significant increases in TMAO in healthy individuals or in those with a chronic condition.”3

This new study is important for eggs, as it demonstrates that food sources of choline may be viewed differently than dietary supplements. “These findings imply that the form of choline ingested may differentially influence gut-microbiota dependent TMAO generation.”6  Although the supplement data need to be replicated, these new data strongly support previous work showing eggs as a food source of choline can be an important part of heart-healthy diets.

You’ve likely heard of the benefits of choline and that it is an important nutrient for brain health throughout the lifespan. Here are some ways choline plays an essential role in overall health:

  • During pregnancy, choline helps the baby’s brain and spinal cord develop properly and supports brain health throughout life.
  • Infants and young children need choline for continued brain development and health.
  • Choline is part of a neurotransmitter called acetylcholine, which is important for muscle control, memory and mood.11
  • Choline is also important for the support of membranes that surround your cells, the transportation of fats throughout the body and for liver health.
  • New research is exploring how choline throughout life may have lasting effects on cognition and prevention of cognitive decline.12

In fact, the 2020-2025 Dietary Guidelines for Americans recommends eggs as a notable source of choline to support brain health and development during pregnancy. Most Americans, about 90%, don’t consume enough choline. Fortunately, eggs are an excellent source. Just one large egg provides the daily choline needs for babies and toddlers, and two large eggs provide more than half of the daily choline needs for pregnant moms.

  1. Blesso, C.N. and M.L. Fernandez, Dietary Cholesterol, Serum Lipids, and Heart Disease: Are Eggs Working for or Against You? Nutrients, 2018. 10(4).
  2. Yang, J.J., et al., Circulating trimethylamine N-oxide in association with diet and cardiometabolic biomarkers: an international pooled analysis. Am J Clin Nutr, 2021.
  3. Thomas, M.S. and M.L. Fernandez, Trimethylamine N-Oxide (TMAO), Diet and Cardiovascular Disease. Curr Atheroscler Rep, 2021. 23(4): p. 12.
  4. Jia, J., et al., Assessment of Causal Direction Between Gut Microbiota-Dependent Metabolites and Cardiometabolic Health: A Bidirectional Mendelian Randomization Analysis. Diabetes, 2019. 68(9): p. 1747-1755.
  5. Wang, Z., et al., Gut flora metabolism of phosphatidylcholine promotes cardiovascular disease. Nature, 2011. 472(7341): p. 57-63.
  6. Wilcox, J., et al., Dietary Choline Supplements, but Not Eggs, Raise Fasting TMAO Levels in Participants with Normal Renal Function: A Randomized Clinical Trial. Am J Med, 2021.
  7. Lemos, B.S., et al., Effects of Egg Consumption and Choline Supplementation on Plasma Choline and Trimethylamine-N-Oxide in a Young Population. J Am Coll Nutr, 2018: p. 1-8.
  8. DiMarco, D.M., et al., Intake of up to 3 Eggs/Day Increases HDL Cholesterol and Plasma Choline While Plasma Trimethylamine-N-oxide is Unchanged in a Healthy Population. Lipids, 2017. 52(3): p. 255-263.
  9. Missimer, A., et al., Compared to an Oatmeal Breakfast, Two Eggs/Day Increased Plasma Carotenoids and Choline without Increasing Trimethyl Amine N-Oxide Concentrations. J Am Coll Nutr, 2018. 37(2): p. 140-148.
  10. Zhu, C., et al., Whole egg consumption increases plasma choline and betaine without affecting TMAO levels or gut microbiome in overweight postmenopausal women. Nutr Res, 2020. 78: p. 36-41.
  11. Wallace TC. A comprehensive review of eggs, choline, and lutein on cognition across the life-span. J Am Coll Nutr 2018, 37(4), 269-285.
  12. Caudill MA, et al. Maternal choline supplementation during the third trimester of pregnancy improves infant information processing speed: a randomized, double-blind, controlled feeding study. FASEB J. 2018;32:2172-2180.

More Articles You’ll Love

SEE ALL