How the Egg Industry Tried to Bury the TMAO Risk

“Metabolomics is a term used to describe the measurement of multiple small-molecule metabolites in biological specimens, including bodily fluids,” with the goal of “[i]dentifying the molecular signatures.” For example, if we compared the metabolic profile of those with severe heart disease to those with clean arteries, we might be able to come up with a cheap, simple, and noninvasive way to screen people. If heart patients happened to have something in their blood that healthy people didn’t, we could test for that. What’s more, perhaps it would even help us understand the mechanisms of disease. “To refer to metabolomics as a new field is injustice to ancient doctors who used ants to diagnose the patients of diabetes” (because the ants could detect the sugar in the diabetics’ urine).

The first modern foray discovered hundreds of substances in a single breath, thanks to the development of computer technology that made it possible to handle large amounts of information—and that was in 1971, when a computer took up nearly an entire room. “[N]ew metabolomics technologies [have] allowed researchers to measure hundreds or even thousands of metabolites at a time,” which is good since more than 25,000 compounds may be entering our body through our diet alone.

Researchers can use computers to turn metabolic data into maps that allow them to try to piece together connections. You can see sample data and a map at 1:28 in my video Egg Industry Response to Choline and TMAO. Metabolomics is where the story of TMAO started. “Everyone knows that a ‘bad diet’ can lead to heart disease. But which dietary components are the most harmful?” Researchers at the Cleveland Clinic “screened blood from patients who had experienced a heart attack or stroke and compared the results with those from blood of people who had not.”

Using an array of different technology, the researchers identified a compound called TMAO, which stands for trimethylamine N-oxide. The more TMAO people had in their blood, the greater the odds they had heart disease and the worse their heart disease was.

Where does TMAO come from? At 2:19 in my video, you can see a graphic showing that our liver turns TMA into TMAO—but where does TMA come from? Certain bacteria in our gut turn the choline in our diet into TMA. Where is the highest concentration of choline found? Eggs, milk, and meats, including poultry and fish. So, when we eat these foods, our gut bacteria may make TMA, which is absorbed into our system and oxidized by our liver into TMAO, which may then increase our risk of heart attack, stroke, and death.

However, simply because people with heart disease tend to have higher TMAO levels at a snapshot in time doesn’t mean having high TMAO levels necessarily leads to bad outcomes. We’d really want to follow people over time, which is what researchers did next. Four thousand people were followed for three years, and, as you can see in the graph at 3:10 in my video, those with the highest TMAO levels went on to have significantly more heart attacks, strokes, or death.

Let’s back up for a moment. If high TMAO levels come from eating lots of meat, dairy, and eggs, then maybe the only reason people with high TMAO levels have lots of heart attacks is that they’re eating lots of meat, dairy, and eggs. Perhaps having high TMAO levels is just a marker of a diet high in “red meat, eggs, milk, and chicken”—a diet that’s killing people by raising cholesterol levels, for example, and has nothing to do with TMAO at all. Conversely, the reason a low TMAO level seems so protective may just be that it’s indicative of a more plant-based diet.

One reason we think TMAO is directly responsible is that TMAO levels predict the risk of heart attacks, strokes, or death “independently of traditional cardiovascular risk factors.” Put another way, regardless of whether or not you had high cholesterol or low cholesterol, or high blood pressure or low blood pressure, having high TMAO levels appeared to be bad news. This has since been replicated in other studies. Participants were found to have up to nine times the odds of heart disease at high TMAO blood levels even after “controll[ing] for meat, fish, and cholesterol (surrogate for egg) intake.”

What about the rest of the sequence, though? How can we be certain that our gut bacteria can take the choline we eat and turn it into trimethylamine in the first place? It’s easy. Just administer a simple dietary choline challenge by giving participants some eggs.

Within about an hour of eating two hard-boiled eggs, there is a bump of TMAO in the blood, as you can see at 4:51 in my video. What if the subjects are then given antibiotics to wipe out their gut flora? After the antibiotics, nothing happens after they eat more eggs. In fact, their TMAO levels are down at zero. This shows that our gut bacteria play a critical role. But, if we wait a month and give their guts some time to recover from the antibiotics, TMAO levels creep back up.

These findings did not thrill the egg industry. Imagine working for the American Egg Board and being tasked with designing a study to show there is no effect of eating nearly an egg a day. How could a study be rigged to show no difference? If we look at the effect of an egg meal (see 5:32 in my video), we see it gives a bump in TMAO levels. However, our kidneys are so good at getting rid of TMAO, by hours four, six, and eight, we’re back to baseline. So, the way to rig the study is just make sure the subjects hadn’t eaten those eggs in the last 12 hours. Then, you can show “no effect,” get your study published in the Journal of the Academy of Nutrition and Dietetics, and collect your paycheck.


Unfortunately, this appears to be part for the course for the egg industry. For more on their suspect activities, see:

For more on the TMAO story, 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:

How to Lower Your Sodium Intake

Reduction of salt consumption by just 15 percent could save the lives of millions. If we cut our salt intake by half a teaspoon a day, which is achievable simply by avoiding salty foods and not adding salt to our food, we might prevent 22 percent of stroke deaths and 16 percent of fatal heart attacks—potentially helping more than if we were able to successfully treat people with blood pressure pills. As I discuss in my video Salt of the Earth: Sodium and Plant-Based Diets, an intervention in our kitchens may be more powerful than interventions in our pharmacies. One little dietary tweak could help more than billions of dollars worth of drugs.

What would that mean in the United States? Tens of thousands of lives saved every year. On a public-health scale, this simple step “could be as beneficial as interventions aimed at smoking cessation, weight reduction, and the use of drug therapy for people with hypertension or hypercholesterolemia,” that is, giving people medications to lower blood pressure and cholesterol. And, that’s not even getting people down to the target. 

A study I profile in my video shows 3.8 grams per day as the recommended upper limit of salt intake for African-Americans, those with hypertension, and adults over 40. For all other adults the maximum is 5.8 daily grams, an upper limit that is exceeded by most Americans over the age of 3. Processed foods have so much added salt that even if we avoid the saltiest foods and don’t add our own salt, salt levels would go down yet still exceed the recommended upper limit. Even that change, however, might save up to nearly a hundred thousand American lives every year.

“Given that approximately 75% of dietary salt comes from processed foods, the individual approach is probably impractical.” So what is our best course of action? We need to get food companies to stop killing so many people. The good news is “several U.S. manufacturers are reducing the salt content of certain foods,” but the bad news is that “other manufacturers are increasing the salt levels in their products. For example, the addition of salt to poultry, meats, and fish appears to be occurring on a massive scale.”

The number-one source of sodium for kids and teens is pizza and, for adults over 51, bread. Between the ages of 20 and 50, however, the greatest contribution of sodium to the diet is not canned soups, pretzels, or potato chips, but chicken, due to all the salt and other additives that are injected into the meat.

This is one of the reasons that, in general, animal foods contain higher amounts of sodium than plant foods. Given the sources of sodium, complying with recommendations for salt reduction would in part “require large deviations from current eating behaviors.” More specifically, we’re talking about a sharp increase in vegetables, fruits, beans, and whole grains, and lower intakes of meats and refined grain products. Indeed, “[a]s might be expected, reducing the allowed amount of sodium led to a precipitous drop” in meat consumption for men and women of all ages. It’s no wonder why there’s so much industry pressure to confuse people about sodium.

The U.S. Dietary Guidelines recommend getting under 2,300 milligrams of sodium a day, while the American Heart Association recommends no more than 1,500 mg/day. How do vegetarians do compared with nonvegetarians? Well, nonvegetarians get nearly 3,500 mg/day, the equivalent of about a teaspoon and a half of table salt. Vegetarians did better, but, at around 3,000 mg/day, came in at double the American Heart Association limit.

In Europe, it looks like vegetarians do even better, slipping under the U.S. Dietary Guidelines’ 2,300 mg cut-off, but it appears the only dietary group that nails the American Heart Association recommendation are vegans—that is, those eating the most plant-based of diets.


This is part of my extended series on sodium, which includes:

If you’re already cutting out processed foods and still not reaching your blood pressure goals, 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, year-in-review presentations:

The Benefits of Wakame Seaweed Salad on Blood Pressure

I used to think of seaweed as just a beneficial whole-food source of minerals like iodine, for which it is the most concentrated dietary source. Indeed, just a daily half-teaspoon of mild seaweeds, like arame or dulse, or two sheets of nori should net you all the iodine you need for the day. But, the intake of seaweeds is advised not only as a whole-food source of iodine, but also, evidently, “for the prevention of lifestyle-related diseases, including cancer, cardiovascular and cerebrovascular disease….” Based on what?

As I discuss in my video Wakame Seaweed Salad May Lower Blood Pressure, the reasoning is that the Japanese live long and eat seaweed, so there is speculation that seaweed might have “influence on life expectancy,” based on suggestive reports. But when we see long lists of the supposed benefits a particular food is purported to have, such as “compounds found in [seaweed] have various biological activities including anticoagulant, anti-viral, antioxidant, anti-allergic, anti-cancer, anti-inflammatory, anti-obesity, and neuroprotective properties,” we need to know if they are based on clinical data, meaning studies with actual people, or so-called preclinical data, that is, from test tubes and lab animals. I mean, what are we supposed to do with a study talking about the effects of “seaweed-restructured pork diets” on rats? Those researchers tried to use seaweed, as well as other ingredients, to “improv[e] the ‘image’ of meat product.” Researchers also tried to add grape seeds to meat, they tried flaxseeds, they tried walnuts, they tried purple rice, and they even tried “thong-weed.”

When you look at epidemiological studies, where you compare the diets and disease rates within a population, you see that Japanese pre-schoolers who eat seaweed tend to have lower blood pressures, suggesting “seaweed might have beneficial effects on blood pressure among children.” That could make sense given all the minerals and fiber in seaweed, but cause and effect can’t be proven with this kind of study. Perhaps other components of the diet that went along with seaweed eating that made the difference.

It’s even harder to do these kinds of studies on adults, since so many people are on high blood pressure medications. University of Tokyo researchers took an innovative approach by comparing the diets of people on different intensities of medication: low-dose of a single blood pressure drug, high-dose of a single drug, and multiple drugs. And, although they all had artificially normalized blood pressure “as a result of effective medication,” those who ate the most fruits and sea vegetables tended to be the ones on the lower dose of a single drug, supporting a dietary role for seaweed. An interesting finding, but why not just put it to the test?

A double-blind, crossover trial found that seaweed fiber lowered blood pressure, apparently by pulling sodium out of the system. Real seaweed couldn’t be used in the study, because the subjects wouldn’t be able to be fooled with a placebo, but why not just put whole powdered seaweed into pills? That was finally attempted ten years later. Compared to doing nothing, subjects receiving a daily dose of dried wakame powder in capsules had beautiful drops in blood pressure. The researchers, however, desalinized the seaweed, taking out about two-thirds of the sodium naturally found in it. So, we still don’t know if eating seaweed salad is actually going to help with blood pressure. What we need is a randomized, controlled trial with plain, straight seaweed. No one had ever done that research, until…they did!

Six grams of wakame, with all of its natural sodium, led to a significant drop in blood pressure, especially in those who started out with high pressure. The subjects experienced only minor side effects and ones that could be expected with increasing fiber intake. A nice thing about whole-food, plant-based interventions is that we sometimes get good side effects, such as the resolution of gastritis (stomach inflammation) some subject had been having, as well as the disappearance of chronic headaches. 


What other foods might help with high blood pressure? See:

For more on preventing and treating hypertension, one of our leading killers, see:

Want more on seaweed and iodine? Check out:

My video Salt of the Earth: Sodium and Plant-Based Diets further addresses the sodium question.

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: