As we age, it is common for brain health to slightly decline. For instance, it may be harder to remember things and multitasking may become more difficult.
Previous research shows there are several healthy choices people can make throughout their lives to potentially slow brain aging.
These include being physically active, prioritizing sleep, managing stress, not smoking, staying mentally stimulated, and following a brain-healthy diet, such as the MIND diet.
When it comes to diet, past studies further show that certain foods may also impact future brain health. For example, studies have reported that consuming a high-fat diet may negatively impact memory formation, and consuming too much salt may lead to cognitive impairment.
“Brain health is at the core of wellbeing,” Michael D. Kendig, PhD, senior lecturer in the School of Life Sciences at the University of Technology Sydney in Australia, told Medical News Today. “We now know that diet has a major influence on brain health over the lifespan, with the ability to protect against, or increase the risk of cognitive decline.”
Kendig is the senior author of a new study review in the journal Nutritional Neuroscience, which found that, while switching to a healthier diet may benefit brain function, it may not fully reverse cognitive issues caused by eating a high-sugar diet, via analysis of data from animal models.
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For this review, researchers analyzed findings from 27 previous studies using rodent models. The animals were all fed high-fat, high-sugar diets for at least 2 weeks. Some rodents were then placed back on their normal healthy food or continued on the high-fat, high sugar diet.
Researchers waited at least 24 hours before scientists assessed the animals’ cognition status.
“Much of the world now eats a dietary pattern characterized by higher than ideal intake of sugar, sodium, and saturated fat,” Kendig said.
“We know that these diets can impair cognitive function — even after a few days or weeks — but not as much is known about what happens to cognition when a bad diet stops, even though this is happening all the time in day-to-day life when people decide to improve eating habits,” he added.
“This led us to review all the studies on this question in preclinical models [in rats and mice],” Kendig explained.
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“Animal models are especially valuable here because in people, multiple aspects of lifestyle are likely to change when someone’s diet improves — perhaps [they] may start exercising more, cut alcohol, and/or generally feel more confident about their ability to look after themselves (self-efficacy). All of these might contribute to improvements in cognition, making it more difficult to isolate the effects of nutrition specifically. The controlled conditions of animal experiments allow us to do this very precisely.”
– Michael D. Kendig, PhD
At this study’s conclusion, researchers did find that rodents that were switched back to a healthy diet performed better on memory tasks than those that continued on the unhealthy diet.
However, scientists determined that memory recovery depended on the composition of the unhealthy diet. Memory recovery was seen in rodents who were fed a high-fat diet, but not in those fed a diet only high in sugar or a combined high-fat, high-sugar diet.
“This was an unexpected result that requires more research,” Kendig explained. “We interpreted this to suggest that recovery of memory was prevented when the unhealthy diets contained sugar — either sugar alone, or combined high fat/sugar.“
“A tentative conclusion is that high-sugar diets may promote forms of cognitive impairment that are more persistent after diet quality improves,” he told us.
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“I think this result points to the fact that high-fat diets impact the brain in different ways than high-sugar or combined high-fat, high-sugar diets,” the scientist added.
“For example, several studies have shown that high-sugar diets may produce a stronger neuroinflammatory response in the brain than high-fat diets. This could explain why unhealthy diets containing sugar promote more lasting cognitive impairments,” he hypothesized.
As these findings all come from animal studies, MNT asked Zack Ramilevich, MD, a neurologist with the Marcus Neuroscience Institute, part of Baptist Health South Florida, whether or not these findings may extend to humans.
“Absolutely, and I believe there is a strong translational basis for it,” Ramilevich, who was not involved in the review, commented.
“We already have robust clinical evidence linking high-sugar high-fat diets to structural changes in the human brain. Specifically, an accelerated volume loss in the hippocampus, our primary memory-forming center. Because the fundamental neuroanatomy and metabolic pathways governing memory are conserved between rodents and humans, it stands to reason that our brains share a similar capacity for recovery. There is no clear biological reason to believe human brains are uniquely excluded from the benefits of removing a metabolic insult.”
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– Zack Ramilevich, MD
Ramilevich said thatthe ideal next step in this research would be transitioning from animal models to trials in humans.
“Furthermore, the next phase of this research needs greater stratification into different types of fats and sugars, rather than just lumping them together as ‘unhealthy food’,“ he continued.
“Since the current data hints that high-fat diets might actually offer better memory recovery than high-sugar diets, future studies must isolate the specific cognitive impacts of fructose versus glucose, and explicitly separate inflammatory saturated fats from possibly beneficial omega-3 fatty acids to see exactly how they interact with our memory centers,” said Ramilevich.
MNT also spoke with Dung Trinh, MD, internist for the MemorialCare Medical Group and chief medical officer of the Healthy Brain Clinic in Irvine, CA, who said while the findings of this study are encouraging, they’re also cautionary.
“It is encouraging because switching to a healthier diet appeared to improve memory performance in animal models,” Trinh, who was likewise not involved in the review, detailed.
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“But it is cautionary because the improvement was incomplete, especially after diets high in sugar or combined high-fat/high-sugar diets,“ he emphasized.
According to Trinh: “The key message is not that brain health is fixed or that damage is irreversible, but that prevention may be more powerful than rescue. Diet quality matters, and prolonged exposure to unhealthy diets may have lasting effects on memory-related brain systems.”
He said it’s important for researchers to continue to find new ways in which people may be able to retain their brain health as they age through their diet because brain aging and dementia risk are among the greatest public health challenges we face, and diet is one of the few risk factors that can be modified across the lifespan.
“We do not yet have a cure for Alzheimer’s disease or most causes of cognitive decline, so prevention and risk reduction are essential,” added Trinh.
“If certain dietary patterns can protect memory systems, reduce inflammation, improve metabolic health, and support vascular function, that gives patients and physicians practical tools long before symptoms begin. The most valuable research is not just about adding years to life, but preserving independence, memory, mobility, and quality of life,” he concluded.
