Canadians are living longer than ever, but a concerning gap is emerging between lifespan and healthspan—the years spent in good health. A scientific study published in JAMA highlights this issue, noting the United States has the largest such gap. With dementia affecting an estimated 42% of Americans over 55, according to the National Institutes of Health, protecting cognitive function is crucial. The good news? A 2024 report in The Lancet states about 45% of dementia cases may be preventable through diet and lifestyle.
The Hidden Danger of Your Afternoon Snack
One everyday habit that quietly threatens brain health is reaching for a sugary treat in the afternoon. Brain health experts point to substantial research connecting high-sugar diets, particularly afternoon consumption, with an increased risk of cognitive decline.
Julie Andrews, a registered dietitian specializing in the MIND diet, explains the mechanism. Sugary foods cause rapid spikes in blood glucose. "Studies show large variations in blood glucose levels over a long period of time can increase dementia risk," she says. This damage stems from harm to the brain's blood vessels, increased body-wide inflammation, and starving brain cells of necessary fuel.
Dr. Alvaro Pascual-Leone, a neurology professor at Harvard Medical School, adds that chronically unstable blood sugar can lead to brain insulin resistance, where brain cells cannot use glucose properly. This condition, sometimes unofficially called type 3 diabetes, can result in memory loss and dementia.
Why Afternoon Spikes Are Especially Harmful
The timing of your sugar intake matters significantly. Dr. Pascual-Leone notes that glucose tolerance is naturally lower in the afternoon compared to the morning, making blood sugar spikes from snacks even more dramatic.
Furthermore, experts agree that a sugary snack later in the day can interfere with sleep quality. Dr. Dung Trinh, Chief Medical Officer of Healthy Brain Clinic, emphasizes that poor sleep is a known risk factor for dementia. Dr. Pascual-Leone clarifies that during sleep, the brain clears out neurotoxic proteins like beta-amyloid and tau. When sleep is disrupted, these proteins accumulate, interfering with neuron communication and increasing dementia risk.
Sugar's impact isn't just metabolic. Dietitian Kelli McGrane notes that high sugar intake overstimulates the brain's dopamine-driven reward system. Over time, this can negatively affect learning, memory, and mood regulation.
Smart Swaps for Brain-Healthy Cravings
The experts stress that you don't need to eliminate sugar entirely—enjoyment is also important for well-being. The key is moderation and smarter choices.
Not all sugars are equal. "Whole fruit comes in a package with fiber, which slows down how fast sugar is absorbed, vitamins, minerals and antioxidants that help protect brain cells," Dr. Trinh explains. This means berries or an apple won't cause the same rapid blood sugar spike as a cookie.
When you do indulge, pair a sugary treat with fiber, protein, or healthy fats to blunt the blood sugar spike. Andrews advises against consuming sugar alone. Also, avoid waiting until you're overly hungry, as this leads to poorer, quicker choices.
For a satisfying sweet snack, experts recommend dark chocolate (rich in brain-supporting flavanols) or a mix of berries and nuts. The berries provide antioxidants, while the nuts offer satiety and stabilize blood sugar.
The consensus is clear: a diet high in sugar elevates dementia risk. By being mindful of intake, especially in the afternoon, and choosing smarter snacks, you can take significant steps to protect your long-term brain health.
