The endothelium is the lining of our arteries and consists of a single layer of tile-like cells. The endothelium is central to artery health and disease. Anything that compromises the health of the endothelium has an immediate effect on the flow of blood to every organ. Atherosclerosis, the obstruction of arteries by cholesterol, is merely the end result of repeated endothelial damage. Every fat and cholesterol laden meal causes an inflammatory storm within the arteries that lasts for many hours and has a measureable effect on endothelial function.
Endothelial cells are continually releasing nitric oxide and many other chemical messengers that control blood flow and blood clotting. Nitric oxide (NO) is the key player. It diffuses into the muscular layer of the artery wall and causes the muscle cells to relax a little. The physics of pipes and fluids dictates that a small increase in the diameter of the vessel results in a big increase in blood flow. This provides for minute to minute adjustment of blood flow so that each area of the body gets enough blood for its needs but no more. There is good reason for this locally acting system. Just having maximum blood flow everywhere at once would result in a fatal drop in blood pressure such as can occur in anaphylactic shock. On the contrary, constricting all of the arteries at once would send blood pressure sky high.
Healthy endothelium has a non-stick “Teflon” quality which assists in blood flow, prevents blood clotting, and resists the uptake of plaque promoting cholesterol. The non-stick endothelium and the associated flexible red blood cells allow blood to flow smoothly through tiny capillaries. Direct observation of blood flowing through these capillaries has shown that eating fats, including polyunsaturated fats, causes blood to sludge and stop flowing.
Our current medical paradigm of endothelial health is focussed almost exclusively on the long term damage that accumulates over years – atherosclerosis – and the physical obstruction to blood flow that this causes. It is well accepted that reducing high cholesterol and other risk factors reduces heart risk within weeks to months by stabilising cholesterol plaques so that they are less likely to burst like pimples. But despite the recognition that endothelial function is central to atherosclerosis and erectile dysfunction, the effect of diet on the hour to hour function of the endothelium is too often ignored. A single fatty meal has bee shown to impair the ability of arteries to dilate for up to five hours (then its time for the next fatty meal).
Meat, other animal “protein” foods and fatty processed foods generate an inflammatory storm within the blood which lasts for many hours. Long term consumption of these foods results in a chronic state of inflammation as part of the so called metabolic syndrome. The inflammatory reaction is in response to toxic levels of fats and other substances within the blood. High levels of insulin and other hormones, high blood sugar levels, and blood milky with fat are part of the body’s attempt to process the rich food. Animal “protein foods” include inflammatory substances other than saturated fat and protein. Carnitine from meats and choline from eggs result in elevated blood levels of the toxic TMAO. Meat also contains endotoxins and both meat and dairy are sources of the foreign inflammatory molecule Neu5Gc. All of this is associated with high levels of oxidative stress within the blood. Under these conditions the “bad cholesterol” particles, LDL, become oxidised and really bad. With all of this going on it is not surprising that the endothelial cells become damaged and unable to maintain their frenetic output of chemical messengers.
Damaged endothelial cells cannot produce enough nitric oxide to dilate arteries fully when more blood flow is required. When blood supply is already compromised, for example by coronary artery disease, a fatty meal may be enough to tip the balance, resulting in angina (heart pain). Endothelial dysfunction also explains the phenomenon of angina in patients with only minimal coronary artery obstruction. Erectile dysfunction in young to middle aged men is an indicator that their endothelium is compromised and unable to release enough nitric oxide to produce an adequate blood flow. More subtle symptoms of endothelial compromise may include decreased exercise capacity, mental clouding and perhaps even conditions such as altitude sickness and migraines. Older persons have many years of accumulated endothelial damage and often quite gross atherosclerosis in which the endothelium is little more than scar tissue. With their nitric oxide production already seriously impaired, any additional short-term assault on the endothelium will have a more marked effect.
Endothelial cells in arteries all over the body are generally maintaining some degree of artery dilation all of time. Dietary factors that impair nitric oxide production will have a whole body effect, increasing the muscle tone of all arteries just a little bit and thus increasing the resistance of the whole vascular system. The body tries to compensate for this by ordering the heart to pump harder to maintain normal flow by raising the blood pressure. Damaged endothelium therefore contributes to hypertension.
As mentioned earlier the endothelial cells do a lot more than just regulate blood flow with nitric oxide, so damaging them has many other consequences. Healthy endothelium down regulates the blood clotting systems so that thrombosis (blood clotting within the vessel) is less likely to occur whereas severely damaged endothelium may even promote thrombosis (as its designed to do when blood vessels are ruptured by trauma). Damaged endothelium loses it’s Teflon quality and both cholesterol particles and white blood cells then stick to it and gain entry into the sub endothelial space between the endothelium and the muscular layer of the artery. This is the first stage of atherosclerosis.
The adverse effects of the typical Australian diet on endothelium is also about what is not being eaten. Whole plant foods are loaded with phytochemicals that are not present in animal products. These phytochemicals include protective substances that neutralise oxidative stress, reduce inflammation and enhance the health of the endothelium, reducing the uptake of cholesterol into the artery wall and the development of atherosclerosis. Nitrate containing green leafy vegetables, such as kale provide the substrate for nitric oxide production. Dr Caldwell Esselstyn now recommends that his patients with severe heart disease consume vegetables such as kale throughout the day to compensate for the impaired capacity of diseased and aged endothelium to produce nitric oxide. The sequence of events from kale to arteries is quite complicated and even involves bacteria in the tongue.