I love this clip. It sums up much of the madness that is the British and American attitude to food, heart attacks and their cause. In my blog What is saturated fat?, I went into what this substance actually is and the positive sides to saturated fat. Reading it won’t take long. As the clip says, there is an assumption that eating saturated fat raises cholesterol and this blocks our arteries, leading to heart attacks. In fact, there is no evidence linking saturated fat to heart attacks. Eating lard, butter or goose fat does not automatically clog up your arteries. Neither does it raise cholesterol. This blog explores why cholesterol is implicated when an artery gets damaged.
Damaged arteries make the body activate the blood clotting system, which forms a blood clot over the damaged artery wall. The clot is called a thrombus. This, of course, is exactly what happens if we cut our knee. Now with the knee, the blood clot forms a scab whilst the skin underneath heals and then the scab falls off. However if the ‘scab’ fell off the artery wall, it would then trundle through the artery until the artery narrowed where it would jam the blood flow – and we would all be dropping like flies from heart attacks or strokes. So instead the clot is drawn into the arterial wall and disposed of.
The popular statin-led theory states that eating saturated fat raises our cholesterol level, which damages the arteries, causing blood clots which need to be removed. In other words, there is too much LDL cholesterol floating about, caused by eating too much butter or lard. As mentioned in the previous blog, LDL cholesterol is known as the bad cholesterol. According to this theory, LDL gets oxidised and then sticks to the artery wall, causing damage. Resultant blood clots build up to form plaques. As cholesterol is found inside these plaques, its presence is taken to mean it caused the plaque. This is a tenuous assumption. Cholesterol is a natural anti inflammatory, a steroid, and part of the body’s defence mechanism, and it might just be that this why cholesterol is there. However, its presence fits the current zeitgeist that high cholesterol causes heart attacks. 1
To be fair to current dogma, a subsection of LDL cholesterol called Lp(a) is clot forming and is attracted to damaged artery walls. High Lp(a) levels do put people at higher risk of heart attacks. But just measuring LDL cholesterol will not give a reading of Lp(a) levels. One can have low LDL cholesterol levels, but still be a terrible risk of having a heart attack or stroke. The previous blog explains more about Lp(a).
There is another theory which has nothing to do with cholesterol or fat in the diet, but does explain how blood clots lead to heart attacks. Some doctors and scientists have not been completely bludgeoned by saturated fat hysteria and their research has discovered things in our blood called pre-endothelial cells. These are produced by our bone marrow, and travel about the blood stream in their billions looking for breaches in the artery walls. Their job is to prevent arterial clots reaching too big a size. If a blood clot has got there first, they cover the clot entirely and transform themselves into new artery walls (the medical name for an artery is endothelium). Usually they are then broken down and the artery wall is as good as new. The theory advanced by scientists at Duke Health.org is that as we age, our bone marrow produces less of these cells, so repair to arteries is slowed down, hence why we are more prone to heart attacks when older. Sadly that link just leads us to the hospital now, so here is a link to a research paper about the same topic, but positing ways of healing damaged arteries: http://hyper.ahajournals.org/content/46/1/7.short With repeated damage to the artery wall, new clots form over the existing ones and slowly large plaques build up. These will either block the artery or break off and trundle through the artery until they reach a narrow point, where they lodge and cause either a heart attack or stroke.
This is one of the mechanisms that statins are effective at dealing with. To prevent over formation of blood clots following a heart attack or stroke, anti-clotting medication is prescribed, eg aspirin, warfarin, ACE inhibitors and statins. But in a situation where LDL cholesterol and saturated fat are reckoned to cause heart attacks, many doctors call for everybody over 50 to be taking a statin for its cholesterol lowering abilities. The trouble is that cholesterol is not the cause of the problem.
Incidentally, it is also the anti-clotting ability of alcohol that gives one of the health benefits of moderate drinking.
To reiterate, arteries are not physically clogged up by eating lard – they are clogged up by scabs on damaged arterial walls 2 . Returning to the assumed fact that eating saturated fat pushes up cholesterol levels, even Ancel Keys, father of the low fat myth, said:
There’s no connection whatsoever between cholesterol in food and cholesterol in blood. And we’ve known that all along. Cholesterol in the diet doesn’t matter at all unless you happen to be a chicken or a rabbit. Ancel Keys, PhD, Professor Emeritus at University of Minnesota, 1997.3
So what is the basis for this myth? Well, the reason Dr Keys referred to rabbits is due to the amusing beginning of research linking saturated fat to heart attacks. An 18th Century Russian researcher, Dr Nikolai Anitschkov, fed rabbits a high cholesterol diet – full of the dreaded animal fats. And indeed their arteries did thicken and fill with cholesterol, and so the myth that saturated fats lead to increased cholesterol levels was given life. Of course, it is another well known fact that bunny rabbits are not lard eaters – it wasn’t Mr McGregor’s lardy thighs that Peter Rabbit was after – but Mr McGregor’s lettuces. In fact, what Dr Nikolai Anitschkov proved is that eating a diet that is very wrong for us raises our cholesterol levels. There is no doubt that this would happen, as one of the many good things cholesterol does for us is lower inflammation in the body, and raised levels indicates there is serious inflammation going on somewhere. If we eat a diet full of transfats, rancid fat, highly processed and refined foods, this is highly unnatural for us and ultimately makes us ill. But to blame raised cholesterol is like seeing many fire engines driving past. The next day huge devastation is found some miles from where we live – so therefore the fire engines, making all that dee dah noise, must have caused all that damage. So excessive chip consumption will not do our arteries any good at all. However there is another culprit, and that will be explored in another blog: stress.
- A theory of why HDL cholesterol is good is that somehow HDL cholesterol is supposed to burrow through into the plaque that forms, extract the LDL cholesterol, burrow back out of the plaque and take the scab to the liver for disposal. [↩]
- What causes the damage to these walls is the subject of another blog [↩]
- Ancel Keys, “Letter-Normal Plasma Cholesterol-Heart disease Theory Is Wrong,” New England Journal of Medicine 325 (1991): 584 [↩]