The story used language which suggests that the diet was responsible for the differences in IQ observed by the researchers — something this study wasn’t designed to prove. And it doesn’t explain, in terms of actual food, how much worse (or better) a diet had to be to be linked to cognitive deficits (or improvements). It didn’t compare the effects of diet with other factors — such as talking to and interacting with children — that have been linked to better cognitive development in other studies.
Parents are very interested in strategies that can help their kids do better in school and get ahead in life. But they don’t always focus on approaches that are well supported by the evidence (remember “Baby Einstein“?). While it makes sense that a nutritious diet might have beneficial effects on brain development, the data so far are preliminary and the effects observed are small. If these limitations aren’t carefully explained, the results might distract parents from other strategies that have better evidence to support their effectiveness. For now, the key take-away from this research is that we need more studies on the long-term effects of early childhood nutrition on development.
There is some research suggesting that diets with a lot of junk food cost less than diets that are rich in fresh fruits and vegetables. This might be a factor that explains why low-income families tend to eat more junk food than families that are well off. Frozen vegetables (and fruits) are also healthy choices and may be a better alternative for low-income families. The story could have brought this factor into the discussion.
Although some data are presented, the results are not clearly explained. For example, the story says that “for every one point increase in processed foods consumption,” the children “lost 1.67 points in IQ.” We are never given any explanation as to what a “one point increase in processed foods” might mean. An extra hot dog each week? An additional serving of mac and cheese? There should have been some attempt to characterize these measurements in terms corresponding to actual food. Similarly, there’s also no discussion of what these IQ differences translate to in terms ability to read, write, and function in a classroom or in other aspects of life. In their study, the authors characterized the associations between diet and IQ as “weak.”
In a sense, this story is all about the potential developmental harms of a high-calorie, nutrient poor diet.
This was an observational study that was incapable of proving cause and effect, but the study is rife with language suggesting that junk food causes lower IQ and healthy food makes IQ go up (e.g. “Processed, Fatty Foods May Dumb Down Your Kids” and “healthful diet for toddlers can boost intelligence.”) The story also never discussed any of the limitations that might cause a study like this to overestimate the effects of diet on IQ. One of these is the fact that families who eat healthily tend to have other attributes that are associated with better cognitive performance, such as parents who read more to their kids and who don’t let them watch as much TV. Although the researchers attempted to adjust for these factors, they acknowledge that they “cannot exclude the possibility of residual confounding.” In addition, kids with learning problems and lower IQ may be more likely to choose foods that are high in fat and sugar despite parents’ attempts to get them to eat healthily. In this case, it’s the low IQ that causes the poor diet, and not the diet which causes the low IQ. The story should have communicated this.
The over-the-top headline crossed the line into fear mongering. The findings were not strong enough to warrant this kind of bold warning.
The story included comments from an dietitian who spoke about the potential detrimental effects of poor nutrition on cognitive development. It would have been helpful to hear from an expert on neurodevelopment, who could have commented on the size of the effects observed and their relevance to real world performance. A comment from a pediatrician about counseling families on healthy diets also would have been helpful.
The story should have mentioned other techniques that can encourage better neurodevelopment. Most notably, time spent talking to and interacting with children in early childhood has been associated with striking differences in later IQ.
The availability of healthy foods is not generally in question, although it may be difficult to find fresh produce in urban areas that aren’t served by grocery stores.
This study is part of a fast-growing field of research into the effects of early childhood nutrition on a variety of later health outcomes. The story could have mentioned this larger context, but it didn’t.
This story is not based on a press release.