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Not the croissants!!

In a new study published in the journal Personality and Individual Differences, a team of French scientists has linked refined carbohydrates to worse cognitive function — even when consumed by young, healthy adults.

Though some diet industry folks might tell you to steer clear from carbs entirely, that's not sound advice. Your body needs carbs for energy, as does your brain.

But not all carbs are created equal. Complex, unrefined carbohydrates like whole grains are an essential piece of a well-rounded diet; industrialized, refined carbohydrates like white bread, on the other hand, which go through a process stripping them of nutritional properties like bran, starch, and fiber — think treacly breakfast cereals and snack cakes — aren't good for much more than a quick sugar hit, as opposed to a sustained energy boost.

And of course, as most quick fixes go, your body will soon be craving more — a habituation that, in this case, may eventually lead to insulin disorders and other chronic ailments, neurological disorders included.

As the scientists note in their study, the introduction of refined carbs into the human diet is a very recent phenomenon, at least in the grand scheme of human history. They didn't come around until well into the 20th century, along with the rest of mass-production culture — and our brains, the scientists say, may well be suffering for it.

"A massive diet switch has occurred in the occidental world since the second half of the 20th century, with a dramatic increase in refined carbohydrate consumption generating numerous deleterious health effects," reads the study's abstract. "Physiological mechanisms associated with refined carbohydrate consumption," it continues, "such as hyperinsulinemia and insulin resistance, may impact cognition in healthy people before overt obesity, metabolic disease onset or dementia."

In other words, because research in this area tends to focus on older adults who have already developed chronic illness, the scientists specifically chose to study younger adults, who may experience negative cognitive impacts of refined carbohydrates prior to developing any long-term condition like diabetes or dementia.

"To date, studies on the link between the long-term consumption of refined carbohydrates and cognition have mainly been carried out on older individuals or in a pathological context," they write. "Nevertheless, early life exposure to refined carbohydrates may be particularly toxic to cognitive functioning, and neurocognitive deficits induced by a diet high in refined carbohydrates may manifest before overt obesity or metabolic disease onset."

In order to close that gap, the researchers enlisted 95 healthy young adults, all between the ages of 20 and 30 and recruited from the University of Montpellier in France. In order to "limit cultural heterogeneity, only individuals declaring European ancestry" were studied.

Each day, a group of three or four participants were asked to show up to the research lab. Upon arrival, they were asked to first take a test called Wechsler's digit symbol substitution cognitive test. They would then have their glucose tested, and after that, they were given one of two very specific breakfasts.

Each extremely French breakfast — which was given to students at random — consisted of 500 calories and was relatively similar. However, there was one big difference: one group's breakfast of whole wheat bread, butter, cheese, a raw fruit and a non-sweetened beverage contained unrefined carbs only, while the other group, who were fed a French baguette made from processed flour, jam, fruit juice and a non-sweetened beverage with sugar available, was made using refined carbohydrates.

Then, after breakfast, there were more tests. At both half an hour and one and a half hours after finishing their morning meal, participants' glycemic indexes were measured again. With the third glycemic check-in, they were asked to take that Wechsler cognitive test for a second time. Individuals were also asked to complete questionnaires that detailed questions about their personal life, history, and diet.

The researchers were able to confirm that the participants who chowed down on the refined flour baguette saw a "significant immediate effect" on their glycemia. Using questionnaires, the researchers were also able to determine that the more someone consumed refined carbohydrates between meals, they experienced lower cognitive performance, an effect that was "maintained when controlling for potential confounding effects such as age, sex, BMI, physical activity, parental home ownership, chronic energy intake of the three mealtimes, and immediate consumption of refined carbohydrates."

As a disclaimer, there are certainly some caveats to this study. As the researchers were careful to note, the participants in the study weren't exactly diverse. It was also pretty heavily rooted in questionnaires, a method of study that can't prove firm cause-and-effect.

Still, if anything, this study serves as a useful reminder of how important it is to focus on the prevention — rather than a reactive treatment — of chronic illnesses. Our bodies, brains included, might depend on it.

"Our study reinforces the belief that the most promising research should focus on prevention in healthy persons," wrote the study authors. "We have shown that cognition in healthy individuals is impacted by chronic refined carbohydrate consumption, indicating that neurocognitive deficits induced by this type of diet may manifest before overt obesity, metabolic disease onset or dementia."

"Thus," they added, "the identification of modifiable factors that could be targeted in interventions to prevent future health impairment is pivotal."

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