Eggs and fish have spent years being shuffled between the nutritional “good” and “questionable” columns. Now, an essential nutrient found in both foods is attracting attention for a completely different reason: its interaction with the gut microbiome may influence inflammation, insulin sensitivity, and blood sugar control.
The nutrient is choline. Scientists have discovered that certain intestinal bacteria can convert choline into trimethylamine, or TMA, a small molecule that appears capable of blocking an inflammatory pathway connected to insulin resistance. The finding is scientifically exciting, but it does not mean that eating a heroic omelet or swallowing choline supplements will prevent type 2 diabetes.
What it does mean is that researchers may have uncovered another piece of the complicated conversation among food, gut microbes, the immune system, and metabolic health. As usual, the gut microbiome has entered the chat and made everything more interesting.
What Is Choline?
Choline is an essential nutrient that supports several basic functions in the human body. Although the liver can produce a limited amount, most people still need to obtain choline through food.
The body uses choline to build phosphatidylcholine and sphingomyelin, two compounds that help maintain cell membranes. Choline is also needed to make acetylcholine, a neurotransmitter involved in memory, mood, muscle control, and nervous-system communication. It contributes to gene regulation, fat transport, liver function, and early brain development as well.
In other words, choline already had an impressive résumé before researchers began asking whether it might affect type 2 diabetes risk.
How Much Choline Do Adults Need?
The established adequate intake is 550 milligrams per day for adult men and 425 milligrams for adult women. Requirements rise to 450 milligrams during pregnancy and 550 milligrams while breastfeeding.
Many Americans consume less than these amounts. That does not automatically mean they are clinically deficient, because individual requirements vary and the body produces some choline internally. However, severe inadequacy can contribute to muscle damage, liver damage, and fat accumulation in the liver.
Which Foods Contain Choline?
Egg yolks are among the most concentrated everyday sources. One large hard-boiled egg provides approximately 147 milligrams, or about 27% of the adult Daily Value. A three-ounce serving of cooked Atlantic cod supplies roughly 71 milligrams.
Other choline-containing foods include:
- Salmon, tuna, and other seafood
- Chicken, turkey, beef, and dairy products
- Roasted soybeans and kidney beans
- Potatoes, broccoli, cauliflower, and Brussels sprouts
- Quinoa, wheat germ, peanuts, and sunflower seeds
That variety matters. Choline is not an exclusive club reserved for eggs and fish, and people following vegetarian or mostly plant-based diets can obtain it from several sources.
How Could Choline Affect Type 2 Diabetes?
Type 2 diabetes develops when cells stop responding efficiently to insulin, the hormone that helps move glucose from the bloodstream into cells for energy. This reduced response is called insulin resistance.
At first, the pancreas compensates by making more insulin. Over time, it may no longer keep up, causing blood glucose to rise. Genetics, physical activity, sleep, body composition, diet, medications, age, and other factors can all influence this process.
Chronic low-grade inflammation is another important contributor. Certain inflammatory signals interfere with insulin pathways, making it harder for muscle, liver, and fat cells to respond normally. Researchers are therefore interested in substances that might calm metabolic inflammation without weakening essential immune defenses.
The Gut Microbiome Connection
When choline reaches the intestines, some gut bacteria can metabolize part of it into trimethylamine. TMA is absorbed into the bloodstream and typically travels to the liver, where an enzyme converts much of it into trimethylamine N-oxide, better known as TMAO.
TMAO has received considerable attention because elevated blood levels have been associated with cardiovascular and kidney problems in some studies. The relationship is complicated, however. Kidney function, diet, microbial composition, existing disease, and the rate at which a person produces or clears TMAO can all affect measured levels.
The new research suggests that TMA and TMAO should not be treated as interchangeable molecules. TMA itself may perform a protective signaling function before it is converted into TMAO.
What the New Study Found
A 2025 study published in Nature Metabolism examined the relationship among dietary choline, gut-produced TMA, inflammation, and insulin resistance. The investigation combined molecular screening, primary human cell experiments, and several mouse models.
In mice eating a high-fat diet, choline supplementation was associated with better glucose tolerance, improved insulin sensitivity, and lower indicators of inflammation. When researchers used antibiotics or a chemical that blocked microbial TMA production, many of these improvements disappeared. That suggested the gut-derived TMA, rather than choline acting alone, was responsible for much of the effect.
TMA Appeared to Block IRAK4
The researchers identified a protein called interleukin-1 receptor-associated kinase 4, or IRAK4, as a direct target of TMA. IRAK4 helps transmit inflammatory signals from Toll-like receptors, which are part of the body’s first line of immune defense.
Under conditions such as a high-fat diet, this signaling pathway can become persistently active. Saturated fatty acids and bacterial components may stimulate inflammatory responses that interfere with insulin action.
TMA appeared to bind to IRAK4 and reduce its activity. This dampened downstream inflammatory signaling and helped restore healthier insulin responses in the experimental models. A pharmaceutical IRAK4 inhibitor produced similar metabolic improvements, strengthening the argument that the protein was an important part of the mechanism.
Think of IRAK4 as an overenthusiastic fire alarm. TMA did not remove the entire immune system from the building; it appeared to turn down one alarm that kept ringing when there was no five-alarm emergency.
Does This Prove Eggs and Fish Prevent Diabetes?
No. The research provides a plausible biological mechanism, not a prescription for preventing type 2 diabetes.
Most of the metabolic experiments were conducted in mice exposed to specially formulated high-fat diets. Human liver cells and immune cells were used to confirm parts of the molecular pathway, but researchers did not conduct a large clinical trial in which people consumed choline and experienced fewer diabetes diagnoses.
Animal studies are valuable because they allow researchers to examine tissues and biological pathways under tightly controlled conditions. Nevertheless, mice metabolize nutrients differently from humans, and experimental doses do not always correspond neatly to ordinary meals.
The benefits also appeared to depend on context. In the study, TMA was particularly relevant during a high-fat dietary challenge. Other research has produced conflicting findings regarding choline, TMAO, egg intake, and glucose metabolism. A result observed under one metabolic condition may not apply to every person or every diet.
Egg Research Has Produced Mixed Results
Some observational studies have linked moderate egg consumption with lower fasting glucose or a lower risk of impaired glucose regulation. Other studies, especially some conducted in the United States, have associated frequent egg consumption with a higher rate of type 2 diabetes.
These differences may partly reflect what people eat with their eggs. An egg served with spinach, beans, tomatoes, and whole-grain toast represents a very different dietary pattern from eggs served with processed meat, fried potatoes, and a sugary coffee drink large enough to require its own cup holder.
Observational research can also be affected by body weight, smoking, activity levels, income, cooking methods, and other lifestyle variables. The egg may be present at the scene without being the nutritional mastermind.
The TMAO Question Requires Caution
The possible anti-inflammatory action of TMA creates an intriguing biological puzzle. Gut bacteria produce TMA, which may inhibit IRAK4, but the liver can convert TMA into TMAO, a metabolite associated in some populations with cardiovascular disease, blood clotting, and kidney dysfunction.
This does not make choline-rich foods inherently dangerous. Large observational studies have not consistently shown that ordinary dietary choline independently causes cardiovascular disease. Fish, despite containing TMAO and TMA precursors, is generally associated with cardiovascular benefits when it replaces processed or fatty meats.
What the contradiction does show is that metabolism cannot always be reduced to “compound good” or “compound bad.” The same biochemical pathway may have different effects depending on microbial activity, liver enzymes, kidney clearance, genetics, medication use, and existing health conditions.
Researchers are interested in whether future treatments could preserve TMA’s IRAK4-inhibiting effect while limiting conversion to TMAO. That possibility is closer to drug development than to a reason for consumers to self-prescribe large choline doses.
Should You Take a Choline Supplement?
The new findings do not establish choline supplements as a treatment or preventive therapy for type 2 diabetes. High supplemental intakes can cause nausea, sweating, low blood pressure, a fishy body odor, liver toxicity, and other adverse effects.
Supplements may be appropriate in specific circumstances, including pregnancy or a medically identified dietary gap, but dosing should be discussed with a physician or registered dietitian. This is especially important for people with kidney disease, liver disease, cardiovascular disease, or multiple medications.
For most adults, a food-first approach is more reasonable. Whole foods provide choline alongside protein, vitamins, minerals, healthy fats, or fiber. They are also less likely to deliver an accidental megadose inspired by an enthusiastic label and a photograph of someone doing yoga at sunrise.
How to Include Choline-Rich Foods in a Diabetes-Friendly Diet
Choline-rich foods can fit comfortably into eating patterns that support metabolic and cardiovascular health. The goal is not to chase one nutrient but to improve the entire meal.
Build a Balanced Breakfast
Pair an egg with non-starchy vegetables, avocado, beans, or a modest serving of whole-grain toast. The protein and fat in the egg may improve fullness, while fiber-rich foods slow digestion and support a more diverse gut microbiome.
Choose Fish Regularly
Baked, grilled, steamed, or broiled fish provides protein with little carbohydrate. Fatty fish such as salmon, sardines, trout, and mackerel also supply omega-3 fatty acids that support cardiovascular health. Breaded and deep-fried fish, unfortunately, cannot put on a salmon costume and claim the same nutritional résumé.
Remember Plant Sources
Soybeans, kidney beans, broccoli, cauliflower, Brussels sprouts, quinoa, peanuts, and potatoes all contribute choline. They also provide fiber and other nutrients that may support glucose regulation and beneficial gut bacteria.
Use the Plate Method
A practical meal might include half a plate of non-starchy vegetables, one-quarter lean protein such as fish or eggs, and one-quarter high-quality carbohydrate such as beans, lentils, quinoa, or another whole grain. Water or an unsweetened drink completes the meal without adding a liquid dessert disguised as hydration.
What Still Works Best for Preventing Type 2 Diabetes?
Choline research is promising, but established prevention strategies have much stronger human evidence. For people with prediabetes and overweight, losing approximately 5% to 7% of starting body weight can substantially reduce the chance of progressing to type 2 diabetes.
Regular physical activity, including about 30 minutes of moderate movement five days per week, improves insulin sensitivity even before dramatic weight loss occurs. Adequate sleep, smoking cessation, stress management, and replacing sugary drinks with water also matter.
Several dietary patterns can support diabetes prevention, including Mediterranean-style, DASH, plant-forward, lower-carbohydrate, and lower-fat approaches. The best plan is nutritionally sound, medically appropriate, affordable, culturally acceptable, and realistic enough to follow after the motivational playlist stops working.
Real-World Experiences: Turning the Research Into Practical Habits
The following composite experiences illustrate how people might apply the broader evidence without treating choline as a miracle cure. They are practical examples, not reports from the laboratory study and not substitutes for personalized medical care.
Experience 1: Upgrading Breakfast Instead of Banning It
A common reaction to a prediabetes diagnosis is to declare war on breakfast. Cereal goes into hiding, bread is interrogated, and eggs are either worshiped or exiled depending on the latest headline.
A more useful experience is to change the composition of the meal. Consider someone who normally eats a sausage-and-egg sandwich with a sweetened coffee. The egg is not necessarily the main problem. Replacing the sausage with spinach and tomatoes, choosing one slice of whole-grain toast, and switching to unsweetened coffee reduces processed meat, refined carbohydrate, saturated fat, and added sugar while preserving a familiar breakfast.
The person may notice better fullness through the morning and less desire to raid the office snack drawer at 10:30. That experience does not prove TMA is blocking IRAK4, but it demonstrates how a choline-rich food can work inside a healthier pattern.
Experience 2: Making Fish the Easy Dinner
Many people like the idea of eating fish twice a week but imagine a recipe involving seventeen ingredients, specialized tweezers, and a television chef shouting about sauce.
In practice, a frozen salmon fillet can be baked with olive oil, lemon, pepper, and herbs. Add roasted broccoli and a small serving of quinoa or beans. The meal provides protein, choline, omega-3 fats, fiber, and relatively little refined carbohydrate.
The most important benefit may be substitution. When fish replaces pepperoni pizza, fried chicken, or processed meat, the nutritional improvement extends far beyond choline. A habit becomes sustainable when it is simple enough to repeat on an ordinary Tuesday, not only when everyone is wearing linen and shopping at a seaside market.
Experience 3: Watching Personal Glucose Responses
People with diabetes often discover that identical foods can produce different glucose responses in different bodies. One person may tolerate a slice of whole-grain toast with eggs, while another sees a larger post-meal rise.
When recommended by a health professional, checking glucose before and after selected meals can reveal useful patterns. The purpose is not to assign moral grades to food. It is to learn whether portion size, carbohydrate type, meal timing, sleep, stress, or activity changes the response.
A ten-minute walk after an egg-and-vegetable breakfast may produce a different result from sitting immediately afterward. The lesson is that metabolism responds to the entire situation, not just one nutrient on the ingredient list.
Experience 4: Feeding the Microbiome, Not Only Adding Choline
Because gut bacteria produce TMA, it may be tempting to focus exclusively on choline intake. Yet the microbiome is shaped by the broader diet. Beans, vegetables, whole grains, nuts, and seeds provide fermentable fibers that support microbial diversity and the production of other potentially beneficial metabolites.
A practical day might include eggs with vegetables at breakfast, lentil soup at lunch, fruit and peanuts as a snack, and fish with Brussels sprouts at dinner. This pattern supplies choline from multiple sources while also delivering fiber, unsaturated fats, and plant compounds.
The experience is less dramatic than taking a “metabolic super-nutrient” capsule, but it is much closer to the evidence. Long-term protection usually comes from meals repeated consistently, not from one ingredient arriving in a cape.
Conclusion
Choline is an essential nutrient found in eggs, fish, meat, dairy products, soybeans, beans, and several vegetables. New research suggests that gut bacteria can convert choline into TMA, which may inhibit the inflammatory protein IRAK4 and improve insulin sensitivity under certain experimental conditions.
The discovery offers a compelling explanation of how a food-derived microbial molecule could influence metabolic inflammation. It may eventually contribute to new nutritional strategies or drugs targeting insulin resistance.
For now, however, the evidence comes primarily from cells and animal models. It does not prove that increasing choline intake or taking supplements prevents type 2 diabetes in humans. Eggs and fish can be valuable parts of a balanced diet, but their effects depend on portions, preparation methods, accompanying foods, and the person eating them.
The most reliable approach remains refreshingly unglamorous: eat mostly minimally processed foods, include fiber-rich plants, choose lean proteins, move regularly, sleep adequately, maintain a healthy weight when possible, and complete recommended blood glucose screening. Science may someday turn the TMA–IRAK4 pathway into a targeted treatment. Until then, dinner should remain dinnernot an unsupervised clinical trial.
