At Real Clear Science, Ross Pomeroy explains how historical “expert knowledge” and government cheerleading pointed in exactly the opposite direction of today’s experts and government regulators:
For decades, the federal government has been advising Americans on what to eat. Those recommendations have been subject to the shifting sands of dietary science. And have those sands ever been shifting. At first, fat and cholesterol were vilified, while sugar was mostly let off the hook. Now, fat is fine (saturated fat is still evil, though), cholesterol is back, and sugar is the new bogeyman.
Why the sizable shift? The answer may be “bad science.”
Every five years, the Dietary Guidelines Advisory Committee, composed of nutrition and health experts from around the country, convenes to review the latest scientific and medical literature. From their learned dissection, they form the dietary guidelines.
But according to a new editorial published in Mayo Clinic Proceedings, much of the science they review is fundamentally flawed. Unlike experiments in the hard sciences of chemistry, physics, and biology, which rely on direct observational evidence, most diet studies are based on self-reported data. Study subjects are examined for height, weight, and health, then are questioned about what they eat. Their dietary choices are subsequently linked to health outcomes — cancer, mortality, heart disease, etc.
That’s a poor way of doing science, says Edward Archer, a research fellow with the Nutrition Obesity Research Center at the University of Alabama, and lead author of the report.
“The assumption that human memory can provide accurate or precise reproductions of past ingestive behavior is indisputably false,” he and his co-authors write.
Two of the largest studies on nutritional intake in the United States, the CDC’s NHANES and “What We Eat,” are based on asking subjects to recall precisely what and how much they usually eat.
But despite all of the steps that NHANES examiners take to aid recall, such as limiting the recall period to the previous 24 hours and even offering subjects measuring guides to help them report accurate data, the information received is wildly inaccurate. An analysis conducted by Archer in 2013 found that most of the 60,000+ NHANES subjects report eating a lower amount of calories than they would physiologically need to survive, let alone to put on all the weight that Americans have in the past few decades.