How to Reduce Your TMAO Levels

Should we be concerned about high-choline plant foods such as broccoli producing the same toxic TMAO that results from eating high-choline animal foods such as eggs?

Choline- and carnitine-rich foods—meat, eggs, and dairy—can be converted by our gut flora into trimethylamine, which in our livers is then turned into TMAO, a toxic compound that may increase our risk of heart failure, kidney failure, and atherosclerosis, or heart attacks and strokes. The good news, though, is that this “opens up exciting new nutritional and interventional prospects” for prevention, as I discuss this in my video How to Reduce Your TMAO Levels.

Okay, so how do we do it? Well, if our gut bacteria can take meat, dairy, and eggs and turn them into TMAO, all we have to do is…destroy our gut flora! We could give people antibiotics to eliminate the production of TMAO. However, that could also kill our good bacteria and “facilitate the emergence of antibiotic-resistant bacterial strains.”

What about probiotic supplements? Maybe if we add good bacteria, they will crowd out the ones that take the meat, egg, and dairy compounds and turn them into the TMA that our liver turns into TMAO. But, that doesn’t work. Adding good bacteria doesn’t seem to get rid of the bad. What if we added new bacteria that could somehow siphon off the TMA made by the bad bacteria? Well, there’s a bacterium inside the guts of cows and sheep that turns trimethylamine into methane. Could we use that bacterium to get rid of some of the trimethylamine from our gut, like a cow fecal transplant? There’s a problem with that. If it didn’t take, you’d have to keep giving it to people: “Continuous administrations may be necessary if subjects do not become colonized.” So, might the fact that Consumer Reports found fecal contamination in every sample of beef it tested be a good thing? No. Methane-producing bacteria may be able to eat up our TMAO, but, unfortunately, these bacteria may be associated with a variety of diseases, from gum disease down to colorectal cancer, as you can see at 2:15 in my video.

If antibiotics and probiotics aren’t going to work to prevent gut bacteria from taking meat, dairy, and eggs and turning them into the trimethylamine, which our liver makes TMAO out of, I guess we have no choice but to cut down on…our liver function!

That was the billion-dollar answer to cholesterol. The same foods—meat, dairy, and eggs—raise our cholesterol, but dietary change isn’t very profitable. So, the drug industry developed statin drugs that cripple the liver’s enzyme that makes cholesterol. Could “pharmacologic inhibition” of the enzymes in our liver that make TMAO “potentially serve as a therapy for CVD [cardiovascular disease] risk reduction”? Trimethylaminuria is a genetic condition in which this enzyme is naturally impaired, in which there is a build-up of trimethylamine in the bloodstream. The problem is that trimethylamine is so stinky it makes you smell like “dead fish.” So, “given the known adverse effects…from sufferers of fish odor syndrome, the untoward odorous side effects of inhibiting this enzyme make it a less attractive [drug] target.”

Do we have to choose between smelling like dead fish or suffering from heart and kidney disease? If only there were some other way we could stop this process from happening. Well, what do those with trimethylaminuria often do to cut down trimethylamine levels? They stop eating animal products.

About a third of those who complain of bad body odor despite good personal hygiene test positive for the condition, but reducing or eliminating meat, egg, and dairy intake can be a real lifesaver. But, given what we now know about how toxic the end product TMAO can be for normal people, cutting down on animal products may not just save the social lives of people with a rare genetic disorder, but help save everyone else’s actual lives.

The “simplest point of intervention” is to simply limit the consumption of foods rich in choline and L-carnitine, which “can be an effective strategy to limit circulating TMAO.” But, wait! We could always try to genetically engineer a bacterium that eats up trimethylamine, but “the simplest and safest recommendation” may just be to eat more healthfully. You can completely eliminate carnitine from the diet, since our body makes all we need, but choline is an essential nutrient so we do need some. Thankfully, we can get all we need in fruits, vegetables, beans, and nuts. “However excess choline, such as that found in eggs, may be worth avoiding.”

Need we worry about high-choline plant foods, like broccoli? Consumption of cruciferous vegetables is associated with a significantly longer life and less cardiovascular disease mortality, as you can see at 5:34 in my video. To see what was going on, researchers took the vegetable highest in choline, brussels sprouts, and had people eat two cups a day for three weeks. What happened? Their TMAO levels actually went down. It turns out that brussels sprouts appear to naturally downregulate that TMAO liver enzyme—not enough to make you stinky, but just enough to drop TMAO.

And, people who eat completely plant-based may not make any TMAO at all—even if you try. You can give a vegan a steak, which contains both choline and carnitine, and there will not even be a bump in TMAO because vegetarians and vegans have different gut microbial communities. If we don’t eat steak, then we don’t foster the growth of steak-eating bacteria in our gut. So forget the cow—how about getting a fecal transplant from a vegan? From a TMAO standpoint, we may not have to eat like a vegan as long as we poop like one.


Can you sense my frustration as I read paper after paper proposing those ridiculous (but profitable!) answers when the safe, simple, side-effect-free solution was staring them in the face the whole time? It makes me think of so many parallels, not the least of which are:

For more on TMAO, the “smoking gun” of diet-microbiome-disease interactions, see:

In health,

Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live presentations:

Kidney Toxins Created by Meat Consumption

As I discuss in my video How to Treat Heart Failure and Kidney Failure with Diet, one way a diet rich in animal-sourced foods like meat, eggs, and cheese may contribute to heart disease, stroke, and death is through the production of an atherosclerosis-inducing substance called TMAO. With the help of certain gut bacteria, the choline and carnitine found concentrated in animal products can get converted into TMAO. But, wait a second. I thought atherosclerosis, or hardening of the arteries, was about the buildup of cholesterol. Is that not the case?

“Cholesterol is still king,” but TMAO appears to accelerate the process. It seems that TMAO appears to increase the ability of inflammatory cells within the atherosclerotic plaque in the artery walls to bind to bad LDL cholesterol, “which makes the cells more prone to gobble up cholesterol.” So TMAO is just “another piece to the puzzle of how cholesterol causes heart disease.”

What’s more, TMAO doesn’t just appear to worsen atherosclerosis, contributing to strokes and heart attacks. It also contributes to heart and kidney failure. If you look at diabetics after a heart attack, a really high-risk group, nearly all who started out with the most TMAO in their bloodstream went on to develop heart failure within 2,000 days, or about five years. In comparison, only about 20 percent of those starting out with medium TMAO levels in the blood went into heart failure and none at all in the low TMAO group, as you can see at 1:21 in my video.

So, those with heart failure have higher levels of TMAO than controls, and those with worse heart failure have higher levels than those with lesser stage heart disease. If you follow people with heart failure over time, within six years, half of those who started out with the highest TMAO levels were dead. This finding has since been replicated in two other independent populations of heart failure patients.

The question is, why? It’s probably unlikely to just be additional atherosclerosis, since that takes years. For most who die of heart failure, their heart muscle just conks out or there’s a fatal heart rhythm. Maybe TMAO has toxic effects beyond just the accelerated buildup of cholesterol.

What about kidney failure? People with chronic kidney disease are at a particularly “increased risk for the development of cardiovascular disease,” thought to be because of a diverse array of uremic toxins. These are toxins that would normally be filtered out by the kidneys into the urine but may build up in the bloodstream as kidney function declines. When we think of uremic toxins, we usually think of the toxic byproducts of protein putrefying in our gut, which is why specially formulated plant-based diets have been used for decades to treat chronic kidney failure. Indeed, those who eat vegetarian diets form less than half of these uremic toxins.

Those aren’t the only uremic toxins, though. TMAO, which, as we’ve discussed, comes from the breakdown of choline and carnitine found mostly in meat and eggs, may be increasing heart disease risk in kidney patients as well. How? “The cardiovascular implication of TMAO seems to be due to the downregulation of reverse cholesterol transport,” meaning it subverts our own body’s attempts at pulling cholesterol out of our arteries.

And, indeed, the worse our kidney function gets, the higher our TMAO levels rise, and those elevated levels correlate with the amount of plaque clogging up their arteries in their heart. But once the kidney is working again with a transplant, your TMAO levels can drop right back down. So, TMAO was thought to be a kind of biomarker for declining kidney function—until a paper was published from the Framingham Heart Study, which found that “elevated choline and TMAO levels among individuals with normal renal [kidney] function predicted increased risk for incident development of CKD,” chronic kidney disease. This suggests that TMAO is both a biomarker and itself a kidney toxin.

Indeed, when you follow kidney patients over time and assess their freedom from death, those with higher TMAO, even controlling for kidney function, lived significantly shorter lives, as you can see at 4:44 in my video. This indicates this is a diet-induced mechanism for progressive kidney scarring and dysfunction, “strongly implying the need to focus preventive efforts on dietary modulation,” but what might that look like? Well, maybe we should reduce “dietary sources of TMAO generation, such as some species of deep-sea fish, eggs, and meat.”

It also depends on what kind of gut bacteria you have. You can feed a vegan a steak, and they still don’t really make any TMAO because they haven’t been fostering the carnitine-eating bacteria. Researchers are hoping, though, that one day, they’ll find a way to replicate “the effects of the vegetarian diet…by selective prebiotic, probiotic, or pharmacologic therapies.”


For more on this revolutionary TMAO story, see:

For more on kidney failure, see Preventing Kidney Failure Through Diet and Treating Kidney Failure Through Diet.

In health,

Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live presentations:

How Not to Die from Diabetes

We’ve known since the 1930s that type 2 diabetes can be prevented, arrested, and even reversed with a plant-based diet. Within five years of following the diet, about a quarter of the diabetic patients in that early study were able to get off insulin altogether.

Plant-based diets are relatively low in calories, though. Is it possible their diabetes just got better because they lost so much weight? To tease that out, we need a study where people are switched to a healthy diet but forced to eat so much food they don’t lose any weight. Then we could see if plant-based diets have specific benefits beyond all the easy weight loss. We had to wait 44 years for such a study, which I then discuss it in my video How Not to Die from Diabetes.

Subjects were weighed every day. If they started losing weight, they were made to eat more food—so much more food in fact that some of the participants had problems eating it all. They eventually adapted, though, so there was no significant weight change despite restricting meat, eggs, dairy, and junk.

Without any weight loss, did a plant-based diet still help? Overall insulin requirements were cut about 60 percent, and half the diabetics were able to get off their insulin altogether. How many years did that take? Not years. An average of 16 days. Only 16 days.

Let’s be clear: We’re talking about diabetics who had had diabetes as long as 20 years and injected 20 units of insulin a day. Then, as few as 13 days later, they were off their insulin altogether, thanks to less than two weeks on a plant-based diet—even with zero weight loss. It’s astonishing. Twenty years with diabetes, and then off all insulin in less than two weeks. Twenty years with diabetes because no one had told them about a plant-based diet. For decades they were just 13 days away at any time from being free.

In my video, I show data from patient #15: 32 units of insulin while on the control diet and then, 18 days later, after switching to the plant-based diet, on no insulin at all. None. Lower blood sugars on 32 units less insulin. That’s the power of plants. And that was without any weight loss. His body just started working that much better once it was provided with the right fuel.

As a bonus, their cholesterol dropped like a rock to under 150. Just as “moderate changes in diet usually result in only moderate reductions in LDL cholesterol levels,” how moderate do you want your diabetes?

“Everything in moderation” may be a truer statement than some people realize. Moderate changes in diet can leave diabetics with moderate blindness, moderate kidney failure, moderate amputations—maybe just a few toes or something. Moderation in all things is not necessarily a good thing.

Remember the study that purported to show that diets high in meat, eggs, and dairy could be as harmful to health as smoking, suggesting that people who eat lots of animal protein are four times as likely to die from cancer or diabetes? If you look at the actual study, you’ll see that’s simply not true. Those eating a lot of animal protein didn’t have just 4 times the risk of dying from diabetes, they had 73 times the risk of dying from diabetes! A 73-fold increase in risk. And those who chose moderation, only eating a “moderate” amount of animal protein, had 23 times the risk of death from diabetes.


The first time someone visits NutritionFacts.org can be overwhelming. With videos on more than 2,000 health topics, where do you even begin? Imagine stumbling onto the site not knowing what to expect and the new video-of-the-day is about how a particular spice can be effective in treating a particular form of arthritis. It would be easy to miss the forest for the trees, which is precisely why I created a series of overview videos that are essentially taken straight from my live, hour-long 2016 presentation How Not to Die: Preventing, Arresting, and Reversing Our Top 15 Killers.

The other videos in this series are:

Inspired to learn more about the role diet may play in preventing and treating diabetes? Check out some of these other popular videos on the topic:

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations: