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. (continue reading)