August 14, 2020
Last week, I attended – virtually, of course, the annual International Conference on Nutrition in Medicine cosponsored by the GW University School of Medicine and the Physician’s Committee for responsible medicine. Dr. Tang’s talk about how our bodies differ from each other based on the composition of the gut micro biome was fascinating. He is the Research Director for Heart Failure and Trasplant at Cleveland Clinic.
He explained that each person has a different nutritional response when eating the same foods. Their sugar, insulin and triglyceride level changes vary from one person to the next. 30-50% of this difference can be explained by genetic factors (i.e. in identical twins). Macronutrient content in the labels only explain about 40% of the response. Something in our bodies, beyond our own genes has a role in how our body processes a particular food. It turns out that it’s the microbes that live inside us. If we characterized our genetic self, we’d be 1/10 human and 9/10 microbes!
Our microbiome changes from birth until weaning, then stabilizes for decades. At 50-60 years old, there seems to be another shift. Across the human race, we know there is only 3% variation in our genes from one person to another, but probably over 50% variation in microbes.
Research is now ongoing about how certain microbes might mimic cells in our bodies, like heart cells. Antibodies can then be produced as a response which then damage our own body organs and cause damage or exaggerate prior damage, as in rheumatic heart disease. A viral infection might also rev up antibody production and contribute to viral myocarditis, severely damaging the heart muscle. The combination of certain microbes and specific genetics for immune responses can make some people more susceptible to these changes.
We are starting to understand that the host and microbe metabolism interact all the time. We have known that after eating fiber, for instance, our own metabolism breaks it down into glucose. Now we know that microbes produce short chain fatty acids (SCFAs) from indigestible fiber, which can affect inflammatory and immune response, affect blood pressure, and improve the barrier function of the gut, limiting certain chemicals from entering the bloodstream.
Much of the recent microbiome research has revolved around TMAO (trimethylamine N-Oxide), since high levels in our blood predict a high risk of death, heart attack and stroke in those with cardiac disease. Diet can account for 10-15% of our blood level of TMAO. Animal products, including eggs, have carnitine and choline, which contain TMA. Certain microbes can extract the TMA, the body absorbs and oxidizes it to TMAO, and excretes it through the kidney. Interestingly, the higher the TMAO level in the blood, the lower the fraction of it is excreted by the kidney. So the level spirals upward with more and more animal products.
Research is ongoing to see if bacteria can be inhibited from extracting the TMA. They could still survive, but just use other fuel sources. Some extra-virgin olive oils have molecules that mimic TMAO and may be able to reduce TMA reactions. As such, they can result in less clotting, kidney damage and heart remodeling. Since humans do not use the same enzymes, this kind of strategy should be safe. Of course more study is needed. The majority of our plasma and urine levels of TMAO are not understood, but perhaps impacting the additional supply from our microbes can help human health.
When we take antibiotics for infections, we unintentionally decrease the number of microbes in our gut. With this, we see the blood levels of TMAO go down. Three weeks later, they rise again. Our microbes are very resilient, so after antibiotics, our own microbes return in the same distribution as before. Along the same lines, probiotics do not have any clear benefit in that it is difficult for any additional bacteria to take root; most are eliminated. Dr. Tang noted that, in fact, there are potential downsides to using probiotics. They may have some components that produce TMAO; yogurt as a probiotic can have sugar which has calories and can thus add to other medical issues. So far the data is mixed.
A key point that he wanted to make is that the TMAO levels in vegans and vegetarians are lower than in others. If they are given carnitine pills, over the course of months, bacteria can be induced to produce TMAO. Regardless of initial diet, those with the highest TMAO levels seem to respond most to a more plant-based diet by lowering their TMAO levels. With this, they also have a reduced risk of heart attacks and strokes. The speaker related that changing to a more plant-based diet can be the equivalent of stopping smoking and has great potential for improved health on a population level.
Studies over the past 5 years have shown that TMAO decreases with caloric restriction, intermittent fasting, and the use of aspirin and statins. In fact, this may explain in part why aspirin and statins reduce the rate of heart attacks and strokes. The TMAO level increases with high protein diets, especially Paleo and Atkins type diets. There are indeterminate results for the use of B12, probiotics, fermented dairy, Mediterranean diet and fecal microbial transplant.
TMAO is only one of the pathways being studied. There is an additional pathway being examined related to phenylalanine that increases our platelet activity and can cause clotting, as well as others.
Dr. Tang’s message was that our bodies – 10% human, 90% microbes – do a balancing act on a daily basis. Whatever we choose for our nutrition then creates a complex interface between our living components. As a cardiologist, he sees tremendous promise in PREVENTION by more plant-based nutrition- not only regarding cardiovascular and kidney disease, but also obesity, diabetes, cancer and inflammatory illnesses.
In other talks at this conference, speakers discussed how a plant-based diet can impact a genetic tendency for early heart attacks and strokes. Exercise, while very important for good health, does not reverse the effects of an unhealthy diet that includes many animal products and highly processed foods. If you have animal products on a daily basis, consider setting aside one day a week, or one meal every day, when you avoid animal products. Each serving of fruits and vegetables that you add on a daily basis decreases your risk of heart disease and death. Prevention and reversal of chronic disease through diet is the GOAL!