Close readers of this website will remember that my sister, Shelley, is addicted to chocolate. Perhaps it’s because of the bacteria in her microbiome. Perhaps it’s due to some weakness in her personality. Perhaps it’s not her fault; perhaps it is her fault. Mostly, I’ve written about the origins of her addiction. How did she come to be this way? (It’s a question that weighs heavily on a younger brother).
There’s another dimension that I’d like to focus on today: the outcome of her addiction. What are the results of being addicted to chocolate? As it happens, my sister is very smart. She’s also very focused and task oriented. She earned her Ph.D. in entomology when she was 25 and pregnant with her second child. Could chocolate be the cause?
I thought about this the other day when I browsed through the May issue of Appetite, a scientific journal reporting on the relationship between food and health. The tittle of the article pretty much tells the story: “Chocolate intake is associated with better cognitive function: The Maine-Syracuse Longitudinal Study”.
The Maine-Syracuse Longitudinal Study (MSLS) started in 1974 with more than 1,000 participants. Initially, the participants all resided near Syracuse, New York. The study tracks participants over time, taking detailed measurements of cardiovascular and cognitive health in “waves” usually at five-year intervals.
The initial waves of the study had little to do with diet and nothing to do with chocolate. In the sixth wave, researchers led by Georgina Crichton decided to look more closely at dietary variables. The researchers focused on chocolate because it’s rich in flavonoids and “The ability of flavonoid-rich foods to improve cognitive function has been demonstrated in both epidemiological studies … and clinical trials.” But the research record is mixed. As the authors point out, studies of “chronic” use of chocolate “…have failed to find any positive effects on cognition.”
So, does chocolate have long-term positive effects on cognition? The researchers gathered data on MSLS participants, aged 23 to 98. The selection process removed participants who suffered from dementia or had had severe strokes. The result was 968 participants who could be considered cognitively normal.
Using a questionnaire, the researcher asked participants about their dietary habits, including foods ranging from fish to vegetables to dairy to chocolate. The questionnaire didn’t measure the quantity of food that participants consumed. Rather it measured how often the participant ate the food – measured as the number of times per week. The researchers used a variety of tests to measure cognitive function.
And the results? Here’s the summary:
Seems pretty clear, eh? But this isn’t an experiment, so it’s difficult to say that chocolate caused the improved function. It could be that participants with better cognition simply chose to eat more chocolate. (Seems reasonable, doesn’t it?).
So the researchers delved a little deeper. They studied the cognitive assessments of participants who had taken part in earlier waves of the study. If cognition caused chocolate consumption (rather than the other way round), then people who eat more chocolate today should have had better cognitive scores in earlier waves of the study. That was not the case. This doesn’t necessarily prove that chocolate consumption causes better cognition. But we can probably reject the hypothesis that smarter people choose to eat more chocolate.
So what does this say about my sister? She’s still a pretty smart cookie. But she might be even smarter if she ate more chocolate. That’s a scary thought.