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:

What Happens if You Add Milk to Tea?

Our endothelium, the inner lining of our blood vessels that controls the function of every artery in our body, “appears to play a critical role in a variety of human disorders, including peripheral vascular disease, stroke, heart disease, diabetes, insulin resistance, chronic kidney failure, [cancer, and blood clots]….” Unfortunately, endothelial cells only live about 30 years, and their replacements don’t seem to function as well. So, “[a]s men and women approach the ages of 40 and 50, there is a progressive decline in endothelial function.” At age 50 or 60, we “can no longer tolerate this risk-factor burden that [we] were once able to tolerate at age 10 or 20,” thanks to this progressive decline in endothelial function.

Or, at least, that’s what we used to think.

As I discuss in my video Tea and Artery Function, there are increasing data to suggest that age is not an immutable risk factor—the decline in artery function is not just an inevitable consequence of aging Researchers did not see the same progressive decline in a Chinese population studied. The older Chinese people in their 60s had the arterial function of young folks in their 20s. “These data suggest that progressive endothelial dysfunction is not an inevitable consequence of aging but might be related to prolonged exposure to environmental factors more prevalent in westernized countries than in China.” What could it be? Traditional Chinese diets include green tea, which has been shown to have a beneficial effect on endothelial function within 30 minutes of consumption, lasting about two hours. It wasn’t the caffeine, which alone had no effect. They suspect it was the flavonoid phytonutrients in the leaves.

Black tea appears to work about just as well as green tea, but then why is green tea associated with lower heart disease risk while black tea is not? In fact, in two British studies, tea consumption was associated with an increased risk of coronary artery disease. Maybe it’s because the Brits commonly drink their tea with milk, whereas green tea is typically drank straight? If only there were a country that drank black tea, but without milk. There is. The Netherlands. In those studies, black tea was associated with the same drop in risk as the green tea studies. So, maybe it is the milk. But you can’t really know until you put it to the test.

Researchers found the “addition of milk to black tea completely prevents the biological activity of tea in terms of improvement of endothelial function.” So, that could explain it. It appears the milk protein casein is the culprit, though soy protein was recently found to have the same nutrient binding effect. The European Society of Cardiology issued a press release about the study showing the protective effect of tea “is totally wiped out by adding milk” and suggested consumers should consider cutting down. Milk-drinkers were not amused: “As long as the reported results are not confirmed in a fair number of humans who drink their tea outside the lab setting, we will continue to add milk to ours.” The researchers responded, challenging the notion that their study wasn’t big enough. They had 16 subjects, and the results were highly significant. Across those 16 people, the “addition of milk to tea not only reduced, but completely blunted the effects of tea….The rationale for drinking tea in a lab setting was that only under these conditions could the influence of other beverages and food be controlled for.” They were doing an experiment after all. Were they supposed to drag the equipment to a Starbucks or something?

“As doctors,” the milky tea drinkers asserted, “we would not prescribe a new drug to patients if it was studied only in one small study. In analogy, milk abstinence should not be recommended to tea drinkers…” They apparently were forgetting that the reason we don’t prescribe drugs without overwhelming evidence is that drugs can kill. So the benefits better outweigh the risks, but what’s the downside of a little milk abstinence?


If this is what one plant can do, imagine the effects of a whole diet centered around plant foods. That’s the subject of my video Plant-Based Diets and Artery Function.

Do be careful about green tea from China if you eat the leaves, though. See Lead Contamination of Tea.

I answer other questions you may have about tea in these videos:

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: