Ever wonder why the headlines keep coming up with different and contradictory things we are supposed to eat and not eat? It’s because nutrition science is notoriously very not good.
Pointing this out is a recent editorial in The Journal of the American Medical Association. (1)
Nutrition science is mostly based on watching what people eat. Since everybody keeps eating, if they are not eating one thing then they are probably eating more of something else. The alternative uncontrolled diets may or may not be evil. Trying to control in a blinded prospective way everything human study subjects eat is very expensive and hard. You can only do studies like this for a short time rather than for a lifetime and you can only measure surrogates of disease propensity, like blood cholesterol or blood pressure. Or you can study animals. That is usually not definitive because they don’t eat people food in their real natural lives for the most part. In humans most of what gets done has to be observational.
Meta-analysis of multiple studies is a technique of gathering together multiple studies of a question and analyzing the larger data pool. This improves the evidence when the input studies are good. But in the case of nutritional studies these authors show that a meta-analysis may actually be worse than any of the individual input studies. They mention several befuddling recent headlines based on new meta-analysis evidence. For example, ” a New York Times commentary proclaiming ‘Butter is Back’ and a Time magazine cover displaying an artistic butter swirl and the bold headline ‘Eat Butter,’ and cited by the 2015 Dietary Guidelines Advisory Committee. The following year, a Gallup poll registered a sharp decline in the number of US adults limiting fat in their diets.”
While we struggle with these incontrovertible facts of nutrition science we should take dietary recommendations we read in the Portsmouth Daily Times &c with a spoonful of sugar and a grain of salt. We should be even slower to institute public policies based on this sloppy stuff.
John DiTraglia M.D. is a Pediatrician in Portsmouth. He can be reached by e-mail- firstname.lastname@example.org or phone-354-6605.