Monday, September 30, 2013

Cholesterol - fact or fiction?

Since my doctor put me on a low cholesterol diet with the possibility (threat?) of prescribing statins if no positive results were seen, I've been doing quite a bit of reading on the subject. In my search for books on how to lower my cholesterol, I found just as many - if not more - with titles like "The Great Cholesterol Con" or "The Great Cholesterol Myth". I had read about fats in books on Sports Nutrition, on food and on diets, such as the Paleo Diet but I hadn't fully made the link with cholesterol as it wasn't something I had ever been particularly worried about. If you are interested, I suggest you read one of the books on the subject for yourselves as the closer you get to the proverbial horse's mouth, the better. I particularly recommend "The Great Cholesterol Myth".

It is very easy to get distracted by conspiracy theorists who leap too enthusiastically on hidden agendas. For example, just because a researcher has some financial connection with the pharmaceutical company that produces the drug he is investigating doesn't automatically mean that the opposite of his or her findings is true or, for that matter, that the research is invalid. It is cause for concern, however, and a sharp eye is required to spot the all too frequent abuses of statistics. Just as Keppler's discovery that the planets actually move in elliptical orbits is a refinement rather than an outright contradiction of the previously held beliefs, I think it is possible to pick out a coherent and convincing narrative amongst all the confusing stories currently being peddled. Part of the confusion seems to stem from the ever persistent (and commercial) debate between high fat and high carb diets. This is my take:

First of all, it's important to bear in mind that cholesterol is fundamental to human life and is found in every cell, with a particularly high concentration in the brain (this accounts for about 25% of all body cholesterol). In fact, the body is able to synthesize cholesterol so it is perhaps no wonder that it can be so notoriously difficult to modify our cholesterol levels through diet, as it may be that the body makes more when it ingests less and vice versa. Statins actually work by inhibiting the metabolic pathways that lead to the manufacture of cholesterol.

The current theory for the cause of cardiovascular disease is that (a) atherosclerotic plaques are caused by elevated levels of cholesterol, particularly transported by the "bad" Low Density Lipoproteins (LDL) in the blood and (b) it is the consumption of saturated fat that leads to these high levels of LDL in the first place. Lastly, (c) statins reduce the level of cholesterol and therefore help fight cardiovascular disease (CVD). It seems reasonable to blame cholesterol for the build up of plaques, as these plaques themselves can be seen to be made up of cholesterol, but is it a question of blaming the firemen for the fire and then firing them?

Surprisingly, while there are no well designed scientific studies supporting either of the hypotheses (a) or (b), a small but significant reduction in CVD mortality rates due to taking statins has been measured in a group of men who have a known history of CVD, appearing to validate (c). Interestingly, the overall mortality rate was unchanged so you are really just swapping one piece of bad news for another (in women, there was no significant difference in either mortality rate).

We've been lead to believe that LDL is "bad" while HDL is "good" because it hoovers up the cholesterol in the bloodstream. In what seems like a parallel of splitting the atom (I kind of lost inetrest when electrons, protons and neutrons turned out to be made up of "quarks" with very silly names) apparently there is a good type of LDL (LDL-A) and a less good type of HDL (HDL-3).

One theory that seems to fit the evidence, is that the arteries are first damaged by high blood pressure, toxins (e.g., from smoking) or free radicals leading to oxidation and inflammation; the cholesterol that is found at the scene of the crime may actually be doing what it is known to be good for - fighting toxins. There is some evidence to suggest that the real villain is in the form of oxidized LDL which sticks to the artery walls and then sets off the process of inflammation. This would mean that the build up of the plaques is actually caused by smoking, hypertension and stress, and not by cholesterol per se. We are all familiar with acute inflammation - when we cut a finger and it goes red around the edges - but chronic inflammtion is when the inflammation - or the cycle of cleaning out the dead cells and replacing them with new ones - simply does not stop.

For the very same reason that cholesterol is good at fighting toxins, having too low levels of cholesterol can actually be bad - for example, one study showed that, in a group of men, the chance of dying of AIDS was actually four times greater for those with low levels of cholesterol (< 160 mg/dL). I'm certainly no expert but treating CVD by lowering your cholesterol seems to me akin to treating an autoimmune disease by shutting down the immune system or "curing cancer" by inhibiting cell regeneration completely. In the case of statins, you are also shutting down the production of coenzyme Q10 which has some very important functions, among which, ironically, is to provide fuel to the muscles and particularly to the heart.

The "Great Cholesterol Myth" also claims that sugar rather than fat - via increased blood pressure and inflammation - is also culpable and the link between heart disease, obesity and daibetes. So now you really have to choose between fat and carbs (because a low fat diet implies a high carb diet and vice versa) and it may be that it is more a question of which fats and carbs you eat.

So what, then? I'm going to continue my experiment of one, to see whether I can reduce my cholesterol levels slightly by eating what I think is, after all, a healthy diet, with just enough carbs to fuel my training. I also plan to keep leading an active life (obviously!) and to try to keep my stress levels down. I might also start to take some anti-oxidants more than anything to help recover from training. Nothing too contraversial then.

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