Snack wisely to protect your memory.

You might notice something in common among the items that earned a spot on our list of six foods you should be eating every day for better brain health, according to a dietitian: they're high in antioxidants, fiber and healthy fats. But one thing they—and most of the core components of the brain-boosting MIND diet—are not super-high on? The glycemic index, which is related to their impact on blood sugar.

Often, foods that deliver a heavy "glycemic load" are rich in refined carbs. And a study published in the journal Alzheimer's & Dementia found that one time of day is most impactful to steer clear of these potentially brain-blasting foods. People who ate a daily afternoon snack high in refined carbs were more likely than their peers who opted for a lower-carb snack to develop dementia or Alzheimer's disease later in life.

To determine this, the researchers used data from the Three-City Study, a French population-based cohort of 9,294 people 65 years of age and older. They chose a representative subsample of 2,777 individuals from this group to complete a food frequency questionnaire for breakfast, lunch, dinner and snacks between meals. Each food consumed was scored on the glycemic index. Taking into account activity levels, total calorie intake, Mediterranean-like diet (their measure of diet quality) and type 2 diabetes status, the scientists discovered that total daily glycemic load and the glycemic load at breakfast, lunch and dinner were not associated with risk for dementia and Alzheimer's disease by the time of their 12-year follow-up. The only eating occasion high in glycemic load that did matter? An afternoon snack.*

*Important to note: Each person was a carrier for apolipoprotein E 𝜀4 allele (APOE-𝜀4), a factor that has been linked to higher risk of cognitive decline. Since there's no easy way for each of us to tell if we are carriers, it certainly can't hurt to implement these health-minded strategies just in case we are.

An older woman looking off in the distance with a torn background in the back
Credit: Getty Images / Thanasis Zovoilis

They believe these stand-alone snacks—such as sweets, cereal bars, cookies and sodas—might lead to more oxidative stress within the body since they're digested quickly and consumed solo (e.g., without fiber-rich side dishes or healthy fat-based dressings) compared to more balanced meals. As a result, they spike blood sugar and create a "favorable environment for insulin resistance," the researchers note. Make it a daily afternoon habit, and this could lead to chronic inflammation and impaired glucose uptake—two factors associated with risk for Alzheimer's disease and dementia.

"During meals, carbohydrates are rarely ingested alone, and their degradation and absorption rates during digestion are modified by the other macronutrients," the scientists note, and point out a fascinating detail about the best way to possibly eat a meal. "The order of food macronutrient intake also changes the glycemic and insulinemic responses," they say. Insulin resistance is more likely "when high-glycemic index carbohydrates (e.g., rice) are eaten first and then vegetables and meat, compared to eating all these foods together."

The Bottom Line

A colorful plate full of whole foods is important any time of day, but this study is a strong reminder that balance is crucial not just at meals, but for snacks as well.

"Eating more complex carbs and keeping meals and snacks balanced with fiber, fat and protein—in addition to those carbs—can help keep blood sugars balanced," says Victoria Seaver, M.S., RD, a registered dietitian and EatingWell's deputy digital editor. "It's a healthy strategy for everyone for overall health, in addition to cognitive health."

Craving some inspiration to mix up your snack strategy? Try our 10 best healthy snack ideas, according to dietitians.