Attempting to define the word “intelligence” is a complex and often difficult endeavor. Is intelligence simply the numerical result measured by an IQ test? How much of a role does working memory play in determining how “smart” you are? What about individuals who may perform worse than their peers on cognitive tests, but demonstrate acutely developed social and emotional acumen?
Scientists and philosophers have grappled with these questions since the notion of hierarchical intelligence differences was first conceived. Raymond Cattell and John Horn bifurcated intelligence into two distinct types: “crystallized intelligence”: knowledge amassed from experience and education and “fluid intelligence”: the capacity for critical thinking and problem-solving in novel situations, without relying on acquired knowledge. Both intelligences intimately interact with one another, and both are malleable over time. However, fluid intelligence is somewhat more stable than its counterpart.
No matter how you define intelligence, one thing is clear: just as you can become “smarter” by studying deeply and widely, there are also a number of influences that can make you “dumber.” For decades, researchers had been documenting a massive increase in average IQ, known as the Flynn effect. However, starting in the 1990s, researchers began to notice a drop in IQ in certain countries. This purported downturn may be related to a number of factors, but perhaps one of the most rampant among them is the prevalence today of high-fructose diets.
In a UCLA study conducted over a six-week period, one group of rats consumed fructose water, while another group consumed fructose water supplemented with DHA, an omega-3 fatty acid that protects against damage to your brain’s synapses. Before this diet began, all of the rats were trained on how to navigate a specific maze. When the rats completed the maze again after the six-week period, the researchers found that those who had consumed only fructose — and no DHA — performed significantly worse than the other test group.
Fernando Gomez-Pinilla, one of the study’s authors, elaborates, “The second group of rats navigated the maze much faster than the rats that did not receive omega-3 fatty acids … The DHA-deprived animals were slower, and their brains showed a decline in synaptic activity. Their brain cells had trouble signaling each other, disrupting the rats’ ability to think clearly and recall the route they’d learned six weeks earlier.”
Furthermore, “insulin had lost much of its power to influence the brain cells,” (a phenomenon known as insulin resistance) in the fructose-only rats. Gomez-Pinilla contends that “fructose is the culprit behind the DHA-deficient rats’ brain dysfunction. Eating too much fructose could block insulin’s ability to regulate how cells use and store sugar for the energy required for processing thoughts and emotions” — ultimately proving detrimental to overall learning and memory.
Of course, while one of the most important steps you can take for your health in general is to cut back on sugar, Gomez-Pinilla says that, “consuming DHA regularly protects the brain against fructose’s harmful effects … It’s like saving money in the bank. You want to build a reserve for your brain to tap when it requires extra fuel to fight off future diseases.”
This study adds to previous research that suggests eating a diet populated with fatty, processed foods with too much sugar content in early childhood can have cumulative effects on IQ. A University of Bristol study found that, “Kids who ate junky fast-food diets at age 3 had a small drop in IQ at age 8.5, compared with kids eating healthy foods. The association persisted even after researchers controlled for other environmental factors that can influence IQ, such as parental education level, maternal diet in pregnancy, socioeconomic status, and stressful life events. For each unit increase in processed food diets, children lost 1.67 points in IQ. By contrast, for each unit increase in healthy diets, children gained 1.2 IQ points.”
The phrase, “You are what you eat,” has been used with such frequency that it has nearly devolved into a stale platitude, but the nugget of truth buried beneath the banality still remains. By extension, if our brains are the seat of intelligence, consuming too much sugar could mean that our ability to think and to reason will begin to resemble its fuel: one-dimensional and artificially derived, deceptively substantial with none of the nutritive value.
