 Almost 2,500 years ago, Hippocrates say that all disease begins in the gut. Feed our gut bacteria right with whole plant foods, and they feed us right back with beneficial compounds like butyrate, which are gut bugs made from fiber. Feed them wrong, on the other hand, and they can produce detrimental compounds like TMAO, which are gut bugs made from cheese, seafood, eggs, and meat. Now, we used to think that TMAO only contributed to cardiovascular diseases like heart disease and stroke, but more recently, it's been linked to everything from psoriatic arthritis to polycystic ovary syndrome. I'm most concerned about our leading killers, though. If we look at the top 10 causes of death in the United States, we know about heart disease and stroke, killers number 1 and 5, but recently an association has been found between blood levels of TMAO and the risks of various cancers, killer number 2. It could be the inflammation caused by TMAO that explains the link between TMAO and cancer, but it could also be oxidative stress, such as free radicals, DNA damage, or a disruption in protein folding. Killer number 4 are chronic obstructive pulmonary diseases like emphysema, and TMAO is associated with premature death in patients with exacerbated COPD, though they suspect it's just due to them dying from more cardiovascular disease. The link to stroke is a no-brainer, no pun intended, because of the higher blood pressure associated with higher TMAO levels as well as the greater likelihood of clot formation in those with atrial fibrillation, and those with higher TMAO levels also appear to have worse strokes and four times the odds of death. Killer number 6 is Alzheimer's disease. Does TMAO even get up into the brain? Yes, TMAO is present in human cerebrospinal fluid which bathes the brain, and indeed the levels are higher in both those with mild cognitive dysfunction and those with Alzheimer's disease and dementia. In the brain, TMAO has been shown to induce neuronal senescence, meaning deterioration with age, increased oxidative stress, and impaired mitochondrial function, all of which may contribute to brain aging and cognitive impairment. Killer number 7 is diabetes, and people with higher TMAO levels are personally 50% more likely to have diabetes, too. Killer number 8 is pneumonia. TMAO predicts fatal outcomes in pneumonia patients even without evident heart disease. And killer number 9 is kidney disease, and TMAO is strongly related to kidney function and predicts fatal outcomes there as well. Over a period of five years, more than half of chronic kidney disease patients who started out with an average or higher TMAO levels were dead, whereas among those in the lowest third of levels, nearly 90% remained alive. OK, OK, so how can we lower the TMAO levels in our blood? Because TMAO originates from dietary sources. We could limit our intake of choline and carnitine-rich foods, but they're quote-unquote so widespread we're talking meat, eggs, and dairy. Therefore, restriction of foods rich in TMAO-creating nutrients may not be practical. I mean, can't we just get a vegan fecal transplant? Vegan donors were kind enough to provide the investigators with a fresh morning sample. If you remember, if you give a vegan a steak, despite all of the carnitine in the meat, they make almost no TMAO compared to a meat eater, presumably because they haven't been fostering steak-eating bugs in their gut. Remarkably, even if you give plant-based eaters the equivalent of a 20-ounce steak every day for two months, only about half start ramping up production of TMAO, knowing just how far their gut flora had to change. The capacity of veggie feces to churn out TMAO is almost non-existent, so instead of eating healthier, why not just get some of that sweet vegan poop off the brown market? In a double-blind or randomized controlled trial, research subjects either got vegan poop or their own poop back. The complete stool production was stirred, not shaken, and then infused through a hose down their nose, and it didn't work. First of all, the vegans they recruited for their study started out making TMAO themselves, as opposed to the other study where they didn't make any at all. This may be because the other study required the vegans to have been plant-based for at least a year, and this study didn't. So yeah, not much of a change in TMAO running through their bodies two weeks after getting the vegan poop, but the vegan poop they got seemed to start out with some capacities to produce TMAO in the first place. So the failure to improve after the vegan fecal transplant could be related to limited baseline microbiome differences, as well as the continuation of an omnivorous diet after the transplant. What's the point of trying to reset your microbiome if you're just going to eat meat? Well, other researchers didn't want to switch people to a plant-based diet, since they knew that alone can change your microbiome and they didn't want to introduce any extra factors. Bottom line, no pun intended. It looks like there may not be any shortcuts. We may just have to eat a healthier diet.