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Saturated fat has been the biggest public health danger apart from smoking for five decades. Ever since the second world war, we’ve known that it caused atherosclerosis, which in turn leads to heart disease, strokes and damaged circulation. It’s just an unfortunate passenger in foods like red meat and fish. If only we could cut it out of our diets altogether, we’d all be a lot healthier.
The trouble is, not a word of that is true. Not one.
So why has it been demonised for so long? And if fat isn’t to blame for heart disease, strokes and obesity, what is?
Fat and atherosclerosis
The ‘lipid hypothesis’ states that saturated fat causes atherosclerosis. This is a hardening and thickening of the arterial walls that narrows the blood vessels, leading to higher blood pressure – inevitably, since the same volume of blood must travel down a thinner tube.
Atherosclerosis is very real, and it affects over 15 million people in America alone. But there’s no real evidence that it’s caused by saturated fat.
Why do people think it is?
In 1913, a Russian physiologist fed high doses of cholesterol to rabbits and found that it was associated with atherosclerotic changes. In rabbits. At several hundred times the normal human dose. The next step was to start looking for atherosclerosis in people with heart disease - and for high-fat diets in people with both. Al three were commonly found together.
Fast forward to 1948 and the American Heart Association was building a case for the ‘Prudent Diet,’ replacing lard and butter with corn oil and soybean oil. We’ve been hearing the same song for all the decades since.
Trouble is, there’s never been any really good evidence that atherosclerosis is eve associated with heart disease deaths – or that it’s caused by saturated fat. We’re looking at a massive case of ‘post hoc ergo proctor hoc’ –just because they were found together, people assumed a connection when there never was one. Japanese natives had a prevalence of atherosclerosis of about 65% in 1952, according to a major study at the time – compared with Americans at 75%, even though the Japanese diet was much lower in animal fats. When corpses from 14 countries around the world were autopsied for atherosclerosis, they all had similar prevalences, no matter where they came from. They came from countries with high fat and low fat diets, and from countries with high and low rates of heart disease.
Fat and Heart Attacks and Strokes
What about heart attacks and strokes? Just because atherosclerosis isn’t the culprit doesn’t mean fat doesn’t cause heart attacks and strokes. This belief is so ingrained that it’s easy to play on it in shockingly ignorant ways. I recently saw a presentation by a man seeking to make converts to vegetarianism make the following argument: ‘I don’t want to eat any fats that are solid at room temperature, because they’ll stay solid in my arteries.’ That’s not the ‘lipid hyposthesis’ –it’s just nonsense. (How long does lard, for instance, stay solid at body temperature? Hold some and find out!) But the lipid hypothesis is so ingrained that it’s easy to sell this stuff.
Fat has been shown to be associated with heart attacks and strokes – but the science was poor. In 1953, Ancel Keys published a study of six countries that showed a correlation between fat consumption and deaths from heart attacks.