A Peak Behind Diet Research

The federal government is releasing its latest five-year revision of the healthy eating guidelines. It’s based on the latest research, of course. I know people who periodically overhaul their eating habits based on what appears to be the latest research. The first problem with this is that they often rely on mainstream media presentations of the research. These presentations often are misleading. They leave out key details and qualifications, and emphasize one or two points far more than the researchers do. The second problem is that the research is not as reliable as many people believe.

This post is devoted to demonstrating the difficulty of devising a good study of healthy eating and explaining why you should use the research with caution.

Our foray into nutrition science demonstrated that studies examining how foods influence health are inherently fraught. To show you why, we’re going to take you behind the scenes to see how these studies are done. The first thing you need to know is that nutrition researchers are studying an incredibly difficult problem, because, short of locking people in a room and carefully measuring out all their meals, it’s hard to know exactly what people eat. So nearly all nutrition studies rely on measures of food consumption that require people to remember and report what they ate. The most common of these are food diaries, recall surveys and the food frequency questionnaire, or FFQ.

Several versions of the FFQ exist, but they all use a similar technique: Ask people how often they eat particular foods and what serving size they usually consume. But it’s not always easy to remember everything you ate, even what you ate yesterday. People are prone to underreport what they consume, and they may not fess up to eating certain foods or may miscalculate their serving sizes.