On full cream milk, sugar, the corruption of science, and the virtue of humility

Some advice for people who are interested in finding the truth (and why I drink whole milk instead of semi-skimmed)

Over 20 years ago, I had a short conversation in a supermarket which, in a small way, was life changing. I was in what was then the Nisa shop in Aberfeldy, and was putting some milk in my shopping basket, and I looked up and saw a lady of my acquaintance. I said something rather apologetic about buying full cream milk instead of semi-skimmed, and she immediately responded by telling me that there was no reason to apologise: full cream milk was healthier than semi-skimmed.

In fact, the lady had actually written a book on the subject of diet. Her name was Maisie Steven, and the first edition of her book The Good Scots Diet had been published a few years before. “And”, she assured me, “Doctor Yellowlees thinks the same.”

Now this was interesting. A doctor who believed in using full cream milk instead of semi-skimmed? This came as a surprise. And furthermore, Doctor Yellowlees was known for taking an interest in nutrition. He was now retired, but in his many years as a GP in Aberfeldy, he had actively encouraged his patients to pursue a healthy diet, and was well known for doing so. And he had written all about it in his book,  A Doctor in the Wilderness.

So, as a result of this conversation, I bought a copy of Dr. Yellowlees’ book. And reading it did change my life, in that it changed my eating habits. Specifically, it made me cut down on anything that contained processed sugar. And one of the sources that Dr. Yellowlees quoted in his argument in favour of cutting down on sugar was a book entitled Pure, White and Deadly by John Yudkin. (I have also continued to full cream milk, though I did notice that as the years passed, semi-skimmed would increasingly becoming the standard default variety of milk. But that’s another story.)

I mention all this because of a fascinating article by Ian Leslie published in the Guardian last week. Read it and weep. It isn’t short, but it’s worth the time. Leslie tells the story of what happened to Yudkin (who was professor of nutrition at Queen Elizabeth College, London, from 1954 tot 1971) because of his views about sugar:

When, in 1957, John Yudkin first floated his hypothesis that sugar was a hazard to public health, it was taken seriously, as was its proponent. By the time Yudkin retired, 14 years later, both theory and author had been marginalised and derided. Only now is Yudkin’s work being returned, posthumously, to the scientific mainstream.”

But the criticism Yudkin faced was not just because of his views on the dangers of sugar. It was also because he questioned the link between high amounts of saturated fat in the diet and heart disease. He argued that fat in the diet (even saturated fat and cholesterol) was not the big problem.

And research has backed him up:

repeated attempts to prove a correlation between dietary cholesterol and blood cholesterol failed. For the vast majority of people, eating two or three, or 25 eggs a day, does not significantly raise cholesterol levels. One of the most nutrient-dense, versatile and delicious foods we have was needlessly stigmatised. The health authorities have spent the last few years slowly backing away from this mistake, presumably in the hope that if no sudden movements are made, nobody will notice. In a sense, they have succeeded: a survey carried out in 2014 by Credit Suisse found that 54% of US doctors believe that dietary cholesterol raises blood cholesterol.

That is shocking enough. But here is something even more shocking:

“The National Heart, Lung and Blood Institute decided to go all in, commissioning the largest controlled trial of diets ever undertaken. . . . At the end of the trial, it was found that women on the low-fat diet were no less likely than the control group to contract cancer or heart disease. This caused much consternation. The study’s principal researcher, unwilling to accept the implications of his own findings, remarked: “We are scratching our heads over some of these results.” A consensus quickly formed that the study – meticulously planned, lavishly funded, overseen by impressively credentialed researchers – must have been so flawed as to be meaningless.”

Note the words “unwilling to accept” and “a consensus quickly formed”.

In the last 10 years, things have started to change. Studies are increasingly questioning the links between dietary fat and heart disease. Yudkin’s Pure, White and Deadly was republished after being out of print for years. And yet, according to Ian Leslie, “Many nutritionists refused to accept these conclusions. The journal that published [a study that questioned the link between a high intake of saturated fat and heart disease] prefaced it with a rebuttal . . . which implied that since [the] findings contradicted every national and international dietary recommendation, they must be flawed.” Leslie adds “The circular logic is symptomatic of a field with an unusually high propensity for ignoring evidence that does not fit its conventional wisdom. “

One of the things that I find particularly striking about the article is what it says about the scientific community and scientific knowledge.

The scientific community is made up of human beings, who sometimes use flawed logic, and who can sometimes be very unwilling to listen to anything that challenges a current consensus. As I read this, what struck me was what Ian Leslie was saying echoed things that I had read about other fields of scientific enquiry – completely unrelated to nutrition and diet.

About the same time that I read Doctor in the Wilderness, I read Darwin on Trial by Philip Johnson, Professor of Law at the University of California, who looked at the evidence for the Darwinian theory of evolution. In the book, Johnson also described the reaction of the scientific community to scientists who questioned the current scientific consensus. It was very similar to the way that the nutrition science community responded to those who questioned the link between dietary fat and heart disease.

More recently, I read Andrew Montford’s The Hockey Stick Illusion which describes the reaction of the climate science community to the work of Steve McIntyre and Ross McKitrick who questioned the way climate scientist Michael Mann (no relation) had analysed his data, thus throwing into doubt his conclusions.

In all three cases – the link between dietary fat and heart disease, the theory of evolution, and climate change – the same pattern emerged. A consensus was challenged, and those who challenged it faced derision, sneering, and personal attack. And in all three cases, the scientific establishment was, at the very least, complicit in that treatment.

Andrew Montford’s The Hockey Stick Illusion has a significant subtitle: “Climategate and the corruption of science.” And that is also what Philip Johnson and Ian Leslie were pointing to. Science was corrupted. As Ian Leslie says, scientific inquiry is “prone to the eternal rules of human social life: deference to the charismatic, herding towards majority opinion, punishment for deviance, and intense discomfort with admitting to error. ” As a result, scientific knowledge, even in the 21st century, is very incomplete.  And yet we think we know everything, because we compare ourselves only with  previous generations.  But in 200 years, people will, no doubt, see us as outdated and ignorant.  

And the moral of the story? Surely it is that it is that we should be suspicious of charismatic figures, cautious about accepting opinions simply because they are those of the majority (i.e. those that are currently fashionable), and willing to listen to those who are challenging prevailing orthodoxies.

Perhaps above, all, the moral is that we should be prepared to admit it when the evidence suggests that we are wrong. There is a lot to be said for open-mindedness and humility.

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