It may be common knowledge that high-sugar, high-fat junk food (think: fried foods, milkshakes, pastries, cakes and cookies) aren’t good for your waistline, but could they also be harming your brain? For older adults, mounting research indicates that a diet high in processed foods — food full of fat, sugar, cholesterol and artificial ingredients — could increase the risk of Alzheimer’s disease for aging adults.
In a 2018 study, scientists from Brock University in Ontario, Canada used mice to test whether diet affects the chances of developing Alzheimer’s. For thirteen weeks, they gave one group of mice a diet high in fat and sugar, and another group a normal diet, according to study results published in Physiological Reports.
When the researchers measured levels of inflammation levels in the brain’s memory center (the hippocampus), and the area of the brain responsible for decision-making and social behavior (the prefrontal cortex), they found that the brains of the mice who ate a high-fat, high-sugar diet had more inflammation, cellular stress and insulin resistance. These factors are all associated with degenerative brain diseases like Alzheimer’s and other forms of dementia.
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In the control group, inflammation levels in the brain rose, too, which the researchers interpreted as a sign that diet isn’t the only factor at play: Aging itself may bring about inflammation, potentially causing some people to develop Alzheimer’s.
According to the study’s authors, the evidence shows that a poor diet may increase the effects of aging.
“These results add to our basic understanding of the pathways involved in the early progression of [Alzheimer’s] … and demonstrate the negative effects of a [high-fat, high-sugar] diet on both the prefrontal cortex and hippocampal regions,” the study team wrote.
A junk food diet as a risk factor for Alzheimer’s disease
Both poor diet and obesity have been linked to Alzheimer’s in the past. In a study in 2017, MRI scans of the brain revealed that people who were obese, smoked, had elevated cholesterol levels, high blood pressure or diabetes had more beta-amyloid in their brains — the sticky protein that builds into plaques in the brains of people with Alzheimer’s.
Having just one of those risk factors increased the likelihood of elevated amyloid levels in the brain by 88 percent; two or more risk factors nearly tripled the likelihood of elevated beta-amyloid plaques. Amongst those risk factors, obesity stood out—it alone nearly doubled the chances of elevated amyloid in later life.
Sugar, in particular, has been implicated in Alzheimer’s disease. Some scientists even refer to Alzheimer’s disease as ‘Type 3 diabetes’ because of the difficulty Alzheimer’s brains seem to have in breaking down glucose, the brain’s main source of energy.
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High levels of blood sugar have been shown to cause memory problems even when they are not at levels that qualify as diabetic and the fluctuation in blood sugar is mild. And of course, Type 2 diabetes itself is a risk factor for dementia, raising the lifetime likelihood of being diagnosed with the disease by 75 to 100 percent. Some scientists have even shown that diabetes drugs show promise in helping to treat Alzheimer’s and possibly other forms of dementia.
The evidence does start to add up — diets high in sugar and fat are likely bad for both the brain and the body. But while this study corresponds with other evidence that shows diet can affect brain health, it was conducted on mice, not people. More research is needed to see if the same findings hold true in humans.
Can a healthy diet help protect the brain from Alzheimer’s?
It’s hard to prove that a healthy diet is enough to prevent brain diseases like Alzheimer’s and dementia but health experts continue to preach the benefits of diets rich in vegetables, whole grains, fruits, olive oil as well as proteins like fish and other seafood, like adherents to the Mediterranean diet traditionally eat.
Some researchers believe that scientists have struggled to make the connection between diet and brain health either because there isn’t any or because past studies have been inappropriately crafted.
Last month, a Nutrition for Dementia Prevention Working Group made up of 27 researchers in the Alzheimer’s and dementia field published a list of dietary recommendations in the journal The Lancet Health Longevity to help the development of future studies examining the link between food and brain health.
Thanks for this article. It isn’t remotely surprising that diets high in sugar are linked with degenerative brain diseases. It would be shocking if such diets weren’t linked to Alzheimer’s. I do think your article unnecessarily demonizes fats. The types of foods you reference (cookies, milkshakes, etc) are generally higher in carbohydrates than they are in fats, and are really bad for you! The study has apparently shown a link between high sugar and high fat diets, and degenerative brain disease. I wonder what they mean by “high fat” as many/most fats are quite healthy, while most most carbs are not. I suspect the results would have been even much worse if they used a high sugar, high carb diet. Of course, processed sugar is entirely carbs and contains no fat.
Do the study again except just feed the mice sugar. Feed another set of mice only fats. Color me unsurprised when your results are different.