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The Link between Heart and Gut

“All disease begins in the gut.” – Hippocrates

We are what we eat, and so are the bugs within us. The contribution of what we eat to the gut microbiota (formerly called gut flora) has a powerful effect on our physiology. The intestine microbiota is the whole Universe of living, breathing and actively participating organisms that are fundamental to both our health and disease processes. We co-evolved, we are symbionts, and we require microbes to survive. Our bugs help us digest foods, break down toxins, make vitamins and create an anti-inflammatory barrier against invaders. Their presence or absence is linked to obesity, heart disease, depression or inflammatory bowel disease. If we count the number of bacteria in our intestines, it’s far greater than the number of cells in the body or even the number of genes in our genome. We have tens of trillions of microorganisms, including about thousand different species of known bacteria with more than three million genes. In fact, our homo sapience DNA constitutes only about 10% of the total DNA we have; the rest are bacterial genes. From the genetic point of view, therefore, the two million unique bacterial genes found in our microbiome makes us more microbial than human. The whole microbiota within us can in total weigh up to two kilos. One-third of our gut bacteria is the same to most people, but two-third, just like our fingerprints is unique to each one of us. In other words, the bacteria in our intestine are like our ID card. As research in this new field progresses, we are gaining more information about the relationship between gut microbiota and our health with a rapidly growing number of disorders linked to microbial imbalance like cardiovascular disease.

Researchers at the Cleveland Clinic noticed that the often quoted association between red meat consumption and the risk of coronary heart disease might be related to more than just saturated fat. In their new study, more than 10,000 people at risk of heart disease were asked to provide blood samples. All participants were followed for three years to see if any of them had a heart attack or died of heart disease. That study and a series of additional experiments led to the conclusion that red meat contains a substance called carnitine which seems to be a culprit. The word carnitine comes from the original Latin word cranes, meaning flesh. It is found in the root of a carnivore, but it can also be found in smaller amounts in fish, chicken and dairy products. The fascinating thing is that carnitine isn’t dangerous by itself. In fact, we need it to build up the cells. The problem begins when carnitine gets metabolised by the intestine bacteria that transform carnitine into so-called TMAO - a substance (amino oxides) in the blood that enables cholesterol to get into artery walls and also prevents the body from eliminating surplus cholesterol. In this particular study with the red meat eaters, it turned out that within a couple of hours after having a steak, TMAO levels in the blood skyrocketed. Interestingly, the outcome was dramatically different when a vegetarian person ate a steak as literally no TMAO appeared in the blood proving that vegans don’t have as many of the gut bacteria needed to make TMAO, as meat eaters. This finding was confirmed when meat eaters were given antibiotics to wipe out their gut bacteria. After eating a steak, they no longer had TMAO in their blood. The reason why bacteria really enjoy the carnitine is probably because they use it as a fuel. In another study, scientists tried to determine whether people with high blood carnitine or TMAO levels were at higher risk of coronary heart disease than those with lower levels. They analysed blood samples from more than 2,500 people, asking if carnitine or TMAO levels may predict heart attacks independently of traditional risk factors like high blood pressure, high cholesterol levels or smoking. The study has shown that blood levels of TMAO predict future risk of a heart attack, stroke and death.

Scientists at the University Medical Centre Groningen in the Netherlands were looking at how much of the variation in BMI (Body Mass Index) and blood lipid levels could be explained by gut bacteria. Having the understanding to what extent the gut microbiota may control our lipids could help develop new treatments to prevent heart disease targeting the unwanted bacterial community.

Researchers collected data from nearly 900 people. All participants were weighed, provided a blood sample to measure full lipid profile (the levels of HDL, LDL, total cholesterol, and triglycerides) and faecal sample to identify the bacteria it contained. Additionally, participants completed questionnaires about their lifestyle habits including diet, medical history and the medication they were taking. The study has identified 34 bacteria in the intestines that may have an impact on weight and blood lipid levels. Interestingly, people who had normal blood lipid levels had more diverse microbiota. The composition of individual gut bacteria was linked to 4% of the variations in HDL cholesterol levels, 6% of the variation in triglycerides and 5% of the differences in body weight despite age, gender and genetics. The study has shown a clear evidence that the gut microbes have a significant influence on both body mass index and blood lipid levels. Our knowledge about gut bacteria is still in its infancy as it takes time to understand such a complex system shaped by a diversity of individual factors like the foods we eat, the area we live in, the way we move our bodies or interact with others. The human gut microbiota is too influential to be ignored. Some researchers already refer to the bacterial community in our gut as an additional independent organ playing an essential role in our overall health and well-being.

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