My Times column on the U-turn over cholesterol and saturated fat:
If you are reading this before breakfast, please consider having an egg. Any day now, the US government will officially accept the advice to drop cholesterol from its list of “nutrients of concern” altogether. It wants also to “de-emphasise” saturated fat, given “the lack of evidence connecting it with cardiovascular disease”.
This is a mighty U-turn, albeit hedged about in caveats, and long overdue. The evidence has been building for years that eating cholesterol does not cause high blood cholesterol. A 2013 review by the American Heart Association and the American College of Cardiology found “no appreciable relationship between consumption of dietary cholesterol and serum [blood] cholesterol”.
Cholesterol is not some vile poison but an essential ingredient of life, which makes animal cell membranes flexible and is the raw material for making hormones, like testosterone and oestrogen. Your liver manufactures most of the cholesterol found in your blood from scratch, and adjusts for what you ingest, which is why diet does not determine blood cholesterol levels. Lowering blood cholesterol by changing diet is all but impossible.
Nor is there any good evidence that high blood cholesterol causes atherosclerosis, coronary heart disease or shorter life. It is not even a risk factor in people who have already had heart attacks. In elderly people — ie, those who have the most heart attacks — the lower your blood cholesterol, the greater your risk of death. Likewise in children.
From the very first, the studies that linked the ingestion of cholesterol and saturated animal fats to cardiovascular disease were not just flawed, but tinged with scandal.
In the 1950s, an upsurge in heart disease in American men (probably caused mostly by smoking) led the physiologist Ancel Keys to guess that dietary cholesterol was to blame. When that seemed not to fit, he switched to saturated fat as a cause of high blood cholesterol. To make his case he did things like leave out contradictory data, shift points on graphs and skate over inconvenient facts. He then got big charities and state agencies on side and bullied his critics into silence.
His most famous study, the seven-country study, started out much larger; he dropped 16 countries from the sample to get a significant correlation. Add them back in and it vanishes. Hidden in his data is the fact that people in Corfu and Crete (in the same country) ate the same amounts of saturated fats, but the Cretans died 17 times more frequently of heart attacks.
In the 1970s, the famous Framingham Heart Study stumbled on the fact that people with high cholesterol over the age of 47 (long before most people have heart attacks) lived longer than those with low cholesterol, and that those whose cholesterol dropped faced higher risk of death. But the consensus ignored this and sailed on.
If challenged to show evidence for low-cholesterol advice, the medical and scientific profession has tended to argue from authority — by pointing to WHO guidelines or other such official compendia, and say “check the references in there”. But those references lead back to Keys and Framingham and other such dodgy dossiers. Thus does bad science get laundered into dogma. “One of the great commandments of science is ‘Mistrust arguments from authority’,” said Carl Sagan.
Eventually, the medical profession began to distinguish between cholesterol and the proteins that carried it, with a distinction emerging between “good” high-density lipoproteins, and “bad” low-density ones. The fatty plaques in arteries are made partly of cholesterol, true, but they form on scars and irregularities caused by other problems: smoking, infections, damage, age. The lipoproteins and cholesterol are part of the repair kit. You don’t blame a fire engine for a fire. We’ve confused effect with cause.
The battle is not over. The medics and scientists who have been insisting for 20 years that the cholesterol emperor has no clothes, and that low-carb, high-fat diets are safer, have been ostracised as quacks and flat-earthers for so long that the habit will die hard. People such as Uffe Ravnskov in Sweden, author of Ignore the Awkward: How the Cholesterol Myths are Kept Alive and Malcolm Kendrick, a GP in Macclesfield, author of The Great Cholesterol Conand Doctoring Data, will not soon be welcomed back into the fold. A scientific consensus can be very intolerant of heretics.
Nonetheless, the medical establishment here too is tiptoeing away from its previous advice to avoid eating cholesterol and saturated fat. It is covering the retreat with a smokescreen, redirecting its fire on trans fats (with more justification), or on sugar. That’s what lies behind all this talk about the dangers of sugar these days — a huge paradigm shift away from the low-fat, low-cholesterol diet. I am not about to say the advice about sugar will also prove wrong.
Indeed, the evidence that insisting on low-fat diets caused people to eat more carbohydrates, and that led to the explosion in obesity and diabetes, looks pretty strong — so far. After all, the main route by which the body lays down fat is to manufacture it from excess sugar in the liver. But why did carbohydrate consumption start to increase so rapidly in the 1960s? At least partly because of the advice to avoid meat and cheese. Obesity and diabetes are the price we have paid for getting fat and cholesterol so wrong.
How about a full, drains-up inquiry into how the medical and scientific profession made such an epic blunder and caused so much misery to people? Consider not just the damage that was done to people’s lives by faulty advice, but to the livelihoods of dairy and beef farmers and egg producers (I declare an interest as a very small producer of free-range eggs). Which has more sugar: an apple or an egg?
But what about statins? In men they lower cholesterol and they prevent heart disease. True, but the connection is not necessarily causal. Statins do a lot of other things, including reducing inflammation, which may be why they deter heart attacks. There are statin sceptics, too, who think the side-effects of taking them are not worth it, and that far too much of the evidence in favour of them comes from the pharmaceutical industry.
We like to think clinging stubbornly to dogmas was a habit of doctors in past centuries, but it still goes on. Medicine needs to get better at changing its mind.