There’s plenty of blame to go around.
Written by: Matt Fitzgerald
The average health-conscious American is a little confused about what constitutes an optimal diet. One source of confusion is the tremendous volume of nutrition information to which we are exposed. It so saturates our culture that even those who avoid reading nutrition books and magazine articles get plenty of it. For example, just yesterday at the grocery store I grabbed a watermelon from a large crate that had a full paragraph about the merits of lycopene (a nutrient with highly touted antioxidant properties) printed on its side.
Those who conscientiously try to heed the news of each new “miracle nutrient” that’s identified and every other sort of nutrition discovery that comes along can easily become overwhelmed. I imagine my fellow shoppers wandering through the supermarket aisles thinking, “Let’s see, to prevent liver cancer I need carotenoids, which are in carrots; and to balance my prostaglandins I need alpha-linolenic acid, which is in salmon; and to lower my cholesterol I need plant sterols, which are in – dammit, I can’t remember!” No one can retain it all, and the quantities of information we do retain are overwhelming enough to make shopping, planning meals, and eating a far more enervating set of activities than they should be.
A second source of confusion is the fact that so much of the nutrition information we get is contradictory. Why can’t the nutrition authorities keep their story straight? There’s a host of reasons. Here are some of them:
Human nutrition is complex. There’s just no getting around the fact that human nutrition is a breathtakingly complex subject. There are tens of thousands of biologically active chemicals at work in the human body, and almost all of them are derived from food in one way or another. Scientists are only able to study one or two small pieces of the intricate puzzle of human metabolism at a time. All too often, they are unable to observe how these pieces are affected by other, unseen pieces, and as a result they draw conclusions that will have to be retracted or revised when these other pieces come into view. Good scientists understand that all of their conclusions are tentative and subject to later revision, but we often have little choice but to base our dietary decisions on the tentative conclusions of nutrition scientists, and it can be frustrating when they are in fact changed.
One example of this dynamic is the story of margarine. Scientists and doctors advocated margarine as a healthier alternative to butter in the 1960s because margarine is lower in saturated fats than butter, and a link between saturated fat and heart disease had been recently discovered. What these doctors and scientists did not know at the time is that trans fats, of which margarine is full, are far worse. The advice to replace butter with margarine has since been retracted.
Scientists are human. While nutrition science in general can’t be blamed for its piecemeal progress, individual nutrition scientists frequently commit avoidable errors that only increase our confusion once they are exposed. More often than you might think, poorly designed nutrition studies and poorly interpreted data yield false conclusions that must be corrected later. Common problems include small sample sizes, faulty data collection methods, lack of adequate placebo controls, and dismissal of unexpected results.
In some cases, studies are designed or interpreted badly with full awareness of the researchers, because they want to please the party (often a food industry corporation) funding the study. In other cases, researchers are so keen on seeing their pet hypothesis validated that, well, they make it right. An example of this latter scenario comes from a large, international study that sought a correlation between cholesterol levels and heart disease in 27 countries. According to the raw data there was only a weak correlation, but inexplicably, in their analysis of this data, the researchers leading the study simply threw out data from countries that defied their expectations and found a much stronger correlation in the remaining data. Years later the correlation between total blood cholesterol levels and heart disease was proven to be much weaker than we were once led to believe.