Anyone who thinks it's enough to rest an argument on "settled science" or a "scientific consensus" ought to read about John Yudkin.
Yudkin was a British professor of nutrition who, in 1972, sounded the alarm about sugar in diets, saying that if sugar were treated like any other food additive "that material would be promptly banned." He said sugar, not fat, was the more likely cause of obesity, heart disease and diabetes.
For his efforts, Yudkin was branded a shill for the meat and dairy industries. His work was dismissed as "emotional assertions," "science fiction" and "a mountain of nonsense." Journals refused to publish his papers. He was uninvited from nutrition conferences and was ridiculed by the scientific community.
"Prominent nutritionists combined with the food industry to destroy his reputation, and his career never recovered," writes Ian Leslie in a lengthy piece titled "The Sugar Conspiracy" that was published recently in The Guardian.
Nutritionists, Leslie explains, had decided that dietary fat was the enemy of good health, based in large part on a huge Seven Countries Study, published in 1970, which looked at 12,770 middle-aged men in countries ranging from the U.S. to Yugoslavia.
"The Seven Countries study had become canonical, and the fat hypothesis was enshrined in official advice," Leslie writes. By 1980, the U.S. government issued its first Dietary Guidelines telling the country to cut back on saturated fats and cholesterol, and Americans dutifully complied.
That's precisely when the nation's obesity rate started to skyrocket. While the obesity rate barely changed from 1960 to 1980 -- going from 13% to 15% -- over the following two decades – 1980-2000 – the rate jumped to 35%.
"At best, we can conclude that the official guidelines did not achieve their objective; at worse, they led to a decades-long health catastrophe," Leslie writes.
Nutritionists are only now grudgingly beginning to admit that their approach to nutrition guidelines could have been, well, wrong, and Yudkin's work is only now being rediscovered. The federal government, for example, quietly admitted recently that there's nothing wrong with eating cholesterol.
So why didn't scientists wise up sooner?
Leslie correctly points out that, despite the patina of pure objectivity, "scientific inquiry is prone to the eternal rules of human social life: deference to the charismatic, herding toward majority opinion, punishment for deviance, and intense discomfort with admitting to error."
That's not to say the scientific method doesn't eventually correct these errors, but the process isn't fast or painless.
For example, when a major study of low-fat diets found that they had no positive effect on women's health, "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," Leslie notes.
Yudkin's plight should be a cautionary tale to anyone who thinks we should blindly follow a scientific consensus, particularly when it involves extraordinarily complex entities like the human body, or when the consensus is used to push public policies that could affect vast populations.
It's not as though the nation's entire obesity problem is the result of the faulty nutrition advice – lots of other factors are at work.
Still, had nutritionists listened to a "fat-denier" like Yudkin four decades ago, we might have avoided the scale of today's obesity epidemic, which has claimed millions of lives.
You can read Ian Leslie's entire article here.
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