A recent study showed that a compound found in red meat called L-carnitine could be responsible for increasing the risk of vascular disease by altering the bacteria found in our guts . Lets look at this study in further detail.
L-carnitine and choline (found in excess amounts in eggs, dairy products) is broken down by our gut microbes into a compound called TMA, which is then converted by liver enzymes into TMAO - associated with cardiovascular disease and atherosclerosis. TMAO is detected in the blood of omnivores but not vegans, following the intake of L-carnitine capsules for three days. It seems a species of bacteria belonging to the genus Prevotella is the main bacterial population that metabolises carnitine into TMAO.
And interesting point is that the presence of TMAO has no effect on the expression of the receptor for LDL (low density lipoproteins or bad cholesterol) or cholesterol production genes. So how can TMAO increase atherosclerosis? In the liver it prevents the breakdown of cholesterol into bile acids. It appears that TMAO also reduces a process called reverse cholesterol transport – the expulsion of excess cholesterol by gut cells, and macrophages in atherosclerotic plaques. TMAO does this by lowering the presence of cholesterol transporters in the gut. Thus if excess cholesterol cannot be eliminated from the circulation by gut cells, or the artery wall by macrophages, the development of atherosclerosis and the risk of cardiovascular disease increases.
So now we know how red meat on its own can increase cardiovascular disease. Over the years it has been documented how the food industry handles red meat to enhance its visual appeal and marketability such as the use of red food colouring and soaking meat in salt water to enrich its flavour. We cannot establish on what scale such tampering has affected the health of the general population. But one thing is for certain, don’t eat meat that looks red.
 Koeth, R. a, Wang, Z., Levison, B. S., Buffa, J. a, Org, E., Sheehy, B. T., … Hazen, S. L. (2013). Intestinal microbiota metabolism of L-carnitine, a nutrient in red meat, promotes atherosclerosis. Nature Medicine, 19, 576–85. doi:10.1038/nm.3145
You’ve heard all the usual health advice to keep your heart healthy or reduce your risk of cancer, but sometimes you are tempted by that mouth-watering piece of cake in the patisserie window or want to miss that workout for the day to catch your favourite TV show. And to be honest there is no harm in occasionally being a little lazy and treating yourself. But maybe you would find it easier to be healthy if you understand why taking such health precautions are good for you. In my previous post, you learned what causes heart attacks and strokes. Now here is how you can prevent them happening to you.
1) Ditch the lard
As mentioned in my previous post, fats are essential to start the atherosclerotic process. If there is too much ‘bad cholesterol’ (otherwise known as low density lipoproteins or LDL) and another type of fat call triglycerides, in your blood from all those hamburgers or a full English breakfast (red meat is particularly high in fat), they will deposit in curved or branching arteries triggering the immune response where macrophages initially consume the fats, clear them from the artery and break them down into cholesterol, which become a vital part of the cell membrane. However the amount of LDL eventually overwhelms macrophages, so they die and deposit in the artery wall contributing to the build up of the atherosclerotic plaque. And why in particular is LDL so dangerous? The clue is in the name, the particles are of a low density and thus are small enough to fit through the spaces between endothelial cells and deposit inside the artery wall, while also being more easily consumed by macrophages. The dying macrophages also contribute to the problem, as their cell membranes become part of the growing plaque increasing the level of cholesterol inside. And it’s not just the fat inside your arteries that creates problems. As more fat is consumed, the body primarily deposits the excess fat around the abdomen resulting in an increase in number and size of fat cells, called adipocytes, which are full of triglycerides and cholesterol. And crucially these adipocytes release chemicals, which increase the aggressive immune activity of macrophages, making them more likely to build up and cause damage in the artery wall.
2) Keep working out
The recommended amount is equivalent to half an hour everyday, my suggestion is to do as much as you can! Research suggests that physical activity; particularly aerobic exercise (such as running, cycling, swimming) can lead to better control of the production of inflammatory signals, which would normally mobilise the immune cells, such as macrophages, responsible for exacerbating atherosclerosis. In fact exercise stimulates the production of anti-inflammatory signals, which dampen down the potentially damaging inflammation, reduce adipocytes, help macrophages to expel cholesterol, reduce growth of the plaque, and in already advanced plaques it can increase the thickness of the fibrous cap (by promoting the growth of smooth muscle cells) therefore it is less likely to rupture and create a blood clot. So it is never too late to start exercising, even as you get older it could save your life!
3) Eat your five-a-day or even more!
Studies show that the more fruit and vegetables you eat, the lower your risk of suffering a heart attack or stroke, particularly with green leafy vegetables and fruits such as apples. Research is ongoing to establish exactly why fruit and vegetables are so beneficial. Early studies suggest a protein called sulforaphane – found in green vegetables such as broccoli – can suppress the activation of endothelial cells, thus it could reduce atherosclerosis by preventing the chain of events that start the disease process.
Earlier I mentioned the dangers of LDL or ‘bad cholesterol’. But there is also ‘good cholesterol’ otherwise called high density lipoproteins or HDL. And as you’ve probably guessed from the name, HDL is not dangerous to the artery wall like LDL because the particles are of a high density and are unable to squeeze in between the endothelial cells and deposit in the artery wall. In addition, HDL serves many benefits. HDL can reduce the inflammatory actions and the entry of macrophages into plaques while increasing their exit from atherosclerotic plaques, thus reducing the size of plaques even if they are already large in size. HDL also promotes the breakdown of cholesterol and its excretion by macrophages, thus reducing the fat content of plaques. So how can you increase your HDL levels? Foods that are known to increase HDL levels in the blood are: fish, high fibre foods (such as oats, fruit, vegetables, grains), nuts, legumes, yogurt, fruit juice, dark chocolate, garlic, and red wine (or dark grape juice if you don’t drink alcohol). And if you have been prescribed statins, keep taking them as they reduce LDL levels while increasing HDL in your blood, and have many anti-inflammatory benefits.
4) Don’t add salt to taste
A high intake of salt increases blood pressure, and the higher your blood pressure the higher your risk of suffering a heart attack or stroke. A higher salt concentration in your blood promotes the diffusion of fluid; primarily water, into the circulation increasing blood volume and thus increasing pressure and potentially damaging the blood vessel wall, particularly the endothelial cells. When pulses of blood are pumped around the body, the arteries need to expand and relax with each pulse of blood that moves through. But if the endothelial cells are damaged, they cannot send signals to stimulate the expansion of the vessel wall further increasing the pressure created by flowing blood and imposing stress on the cells. All of these events increase inflammation creating the conditions for atherosclerosis to begin and further increase blood pressure.
5) Don’t give in to your sweet tooth
There is no doubt about the association between high sugar intake and cardiovascular disease, but we still don’t really know why this is the case. Studies performed so far suggest that high blood glucose levels can increase inflammation, promote the entry of macrophages into the artery wall and possibly interfere with the expulsion of cholesterol by macrophages. It also appears that LDL is increased in diabetics, thus sugar and cholesterol may work together to promote atherosclerosis. While more studies are needed to firm up these conclusions, the link between diabetes and cardiovascular disease is very clear so don’t tickle you sweet tooth too often!
6) Limit the booze
Early studies demonstrate that light drinking (up to the recommended 2-3 units of alcohol a day) reduces atherosclerosis, and the risk of strokes and heart attacks, but consuming higher amounts of alcohol on a regular basis increases atherosclerosis significantly. But a recent small-scale study published by New Scientist  showed that when regular social drinkers gave up alcohol for a month, they experienced a large drop in liver fat, blood glucose and cholesterol, and improved their sleep quality and concentration, although more scientific evidence is needed to back up these results. So you can still enjoy that tipple, but only in moderation.
Any questions? Please comment below
Dr. Anusha Seneviratne
My research is funded by the British Heart Foundation. To donate click sponsor me below.
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