There’s some people out there, smart ones even, who don’t believe that elevated cholesterol levels are dangerous for your health. One reader recently read The Cholesterol Myth by U. Ravnskov, MD, PhD and wrote to ask my opinion on his anti-cholesterol rhetoric. Is the whole cholesterol thing a scam, a phony issue, a myth?
The mainstream story goes like this: Animal products and some tropical oils have high levels of saturated fat. Eating a lot of saturated fat increases blood cholesterol levels. Having elevated blood cholesterol increases the chance of dying from a heart attack.
But, well, does it? Does eating saturated fat in the form of meat and whole milk and cheese and eggs and all that other good stuff really lead to heart attacks? Ravnskov’s point is that there is surprisingly little support from good randomized and controlled clinical trials to prove it.
But since Ravnskov stepped down from his soapbox there’s been some new evidence supporting the role of dietary intake of saturated fat (and that means cholesterol as the body sees it) in the development of heart disease. A Harvard study reviewed the literature to date (as of June, 2009) and pooled the existing research to look for an overall effect of replacing saturated fat with poly-unsaturated fat in the form of vegetable and fish oils.
They found that people who replaced saturated fat in their diets with poly-unsaturated fat had a 19% reduced risk of heart disease troubles like heart attacks. For each 5% energy increase of poly-unsaturated fat in the diet substituting for saturated fat, there was a 10% reduction in risk. It was “dose dependent” so a little reduction of saturated fat helped a little and a big reduction helped a lot. The longer people stuck to the diet change, the greater the benefit that was seen.
The risk of heart disease was reduced by 24% for each 1 mmol/l reduction in total cholesterol. This finding is consistent with results of observational studies of total cholesterol levels and the risk of heart disease.
The Harvard review provides proof from randomized, controlled clinical trials – the gold standard for medical evidence that reducing saturated fat in the diet (and thus cholesterol) and replacing it with poly-unsaturated fat reduces heart attacks. It’s not a myth.
And nobody’s talking drugs here. This is about diet. It’s about what you put into your body.
But there’s one caveat. Because the trials included in this study looked only at replacing saturated with poly-unsaturated fat, it’s not possible from this evidence alone to distinguish between the benefits of reducing saturated fat and the benefits of increasing poly-unsaturated fat. It’s likely they work in concert.
Other studies looking at replacing saturated fat with carbohydrates weren’t so supportive. This may be because of the choice of carb. If participants were eating more refined grains and sugar, then the inflammatory condition inspired by their choices may have counterbalanced any beneficial effect of lowering saturated fat. We know that fructose without fiber (Dr. Lustig’s poison without its antidote) increases triglycerides and the small, dense (ie dangerous) form of LDL. That small form of LDL is what climbs up under the lining of blood vessel walls and forms atherosclerotic plaques of cholesterol that eventually rupture causing a heart attack.