Alarming new research in the US has shown that it is not just the consumption of saturated fats and cholesterol in red meat which predisposes meat-eaters to developing heart disease. Following tests, new and startling evidence has emerged which appears to show that saturated fats and cholesterol play only a minor role in the causation of heart disease.
The main culprit is in fact, a previously little-researched chemical produced by the bacteria in the intestines following the consumption of red meat. This chemical is rapidly converted by the liver into another chemical called TMA. It’s this which then enters the blood stream and increases the risk of heart disease.
In an experiment, five meat eaters and one vegan who had not eaten meat for over a year each ate a steak. They were then all immediately blood tested. The blood results revealed a simultaneous soaring of TMAO levels in all but the vegan. Further studies showed that regular red meat eaters generally carry TMAO in their blood whereas vegans and vegetarians do not. Meat eaters who took carnitine tablets readily made TMAO. Research using mice showed that those who were fed red meat displayed high levels of TMAO in their blood and subsequently developed heart disease whereas those on a meat-free diet did not.
The ramifications of the studies are intriguing. New treatments for heart disease could be developed including an antibiotic which could eradicate the bacterial cause of TMAO production altogether. Screening for TMAO in the blood could be used to assess a patient’s risk of developing heart disease.
There are still many unanswered questions, however. It is not definitively proven that TMAO causes heart disease, and at this point in time the gut bacteria which cause its production have not yet been identified. Although concerned by the researchers’ findings, scientists are still keen to stress that red meat does contain protein and B vitamins, both of which are important for good health.
A further independent study has shown that the substance carnitine could also be responsible for heart disease. Carnitine is also found in chicken, fish, and dairy products, although in smaller quantities. It is also contained in some health food supplements and energy drinks such as those used by bodybuilders and sportsmen. Carnitine itself is not dangerous. It is when it enters the gut and is metabolised by intestinal bacteria that problems arise, as it is then converted to TMAO in the bloodstream.
It would appear then that those of us who follow a vegan diet are not as able to produce TMAO as meat eaters and therefore hypothetically do not harbour as many of the requisite gut bacteria responsible for its production.
The researchers then gave the meat eaters antibiotics which killed off virtually all of their gut bacteria. They they consumed red meat and carnitine pills again but this time the blood tests revealed no TMAO in their blood at all. It was therefore concluded that the gut bacteria were responsible for the production of TMAO.
So, are people with high levels of TMAO or carnitine in their blood at higher risk of heart disease? Studies of over 2,500 subjects showed that high levels of both TMAO and carnitine did predict heart attacks independently of high blood pressure, smoking, or raised cholesterol. However, on further analysis, it was deduced that this effect was solely down to TMAO.
It is therefore theorized by the researchers that TMAO facilitates the osmosis of cholesterol across the artery walls and into the blood, whilst simultaneously preventing the excretion of excess cholesterol and it is this double whammy which leads to the increased risk of heart disease and heart attack.