Sweet Tooth, Foggy Brain? The Surprising Link Between Diet and Memory

You are what you eat — and that applies to your brain, too. (Photo: Getty/Yahoo Health)

Research has shown it time and again: Weight gain isn’t good for your health. And according to a new study, it could be bad for your mind as well.

The study, published in the journal JAMA Neurology, shows a strong association between insulin resistance (often linked to weight gain) and a decline in memory function.

For the research, scientists studied the brain scans of 150 people with a median age of 60 at risk of developing Alzheimer’s disease but who didn’t have memory loss. The scans showed that people who had higher insulin resistance used less blood sugar in areas of the brain that are the most susceptible to Alzheimer’s. Why this is a problem: When there is less blood sugar in the brain, it doesn’t function as well, researchers say.

Insulin is a hormone that helps move glucose (aka blood sugar) from your blood into your cells for your body to use as fuel. The pancreas secretes insulin into the bloodstream, but when insulin resistance occurs, there is not enough insulin to move the blood sugar to the cells. As a result, the pancreas creates more insulin to move the blood sugar along.

Diet plays a role in all this because foods high in sugar and fat can cause blood sugar spikes, causing your insulin response to kick into overdrive to convert the nutrients into energy. But when your body doesn’t need any more energy, the rest is stored as fat. Too many blood sugar spikes can then lead to insulin resistance. (However, everyone is different; there are many factors that affect how resistant the body becomes to insulin over time. It’s best to try to keep your blood sugar on an even keel as much as possible to prevent spikes from happening.)

Related: Early Signs of Alzheimer’s Disease Found in Patients as Young as 20

“In Alzheimer’s disease, many brain regions start using less and less blood sugar,” study co-author Auriel Willette, PhD, a food science and human nutrition professor at Iowa State University, tells Yahoo Health. “It’s like trying to drink a thick milkshake through a straw that keeps shrinking.”

Willette says insulin may be giving a boost to processing blood sugar in key areas in the brain that do complex processing. If insulin resistance takes place, and there isn’t enough insulin to do the job that it should, he says forming memories can become harder. Over time, those brain cells might begin to starve and die off.

Insulin resistance is a hallmark of pre-diabetes, type 2 diabetes, and obesity. And while scientists say genetics could be at play, research has found that diet also has a role.

A review published in the journal Current Diabetes Reports found that eating a high-fat diet puts people at a greater risk of developing insulin resistance. Artificial sweeteners may also indirectly contribute to insulin resistance. A 2013 study published in the journal Diabetes Care discovered that insulin levels rose by 20 percent in people who were given the artificial sweetener sucralose (found in Splenda). If that happens repeatedly, researchers say it could cause more food cravings, insulin resistance, and weight gain.

Filmmaker Max Lugavere, who is working on a documentary called Bread Head about the role of diet and exercise on cognitive decline, tells Yahoo Health he isn’t shocked by the new findings. “When there is something metabolically awry, it could impact brain health,” he says. “Studies like this are meaningful.”

“Obviously a diet high in refined carbs and sugar … we know is one of the main causative factors in Type 2 diabetes, which is reaching high proportions globally,” Lugavere adds, so this study only serves as further evidence that cutting these kinds of foods out of our diets can help keep our brains healthy.

Luckily, registered dietitian nutritionist Beth Warren, author of Living a Real Life With Real Food, says we can do something about it. “Food choices come hand in hand with balancing blood sugar levels and decreasing the risk of insulin resistance,” she tells Yahoo Health.

Warren says it’s often helpful to make healthier swaps, like 100 percent whole-grain bread over white bread (the whole-grain version is a low-glycemic carbohydrate, which won’t cause as much of a blood sugar spike), and to eat every three hours to regulate your blood sugar.

Related: Can You Prevent Dementia Through Nutrition?

New York City registered dietitian Jessica Cording also recommends pairing foods that contain carbohydrates with protein and a healthy fat (think: an apple with almond butter). “Protein and fat has a buffering effect,” she tells Yahoo Health. “They help minimize blood sugar spikes as they slow digestion, promote satiety, and help maintain a slow-burning energy.”

Willette says moderate exercise can help as well. “You don’t need to do intense gym workouts,” he says, adding that all you need is 30 minutes a day, three days a week. “The more our muscles work, the more they sop up excess blood sugar all the time and prevent insulin resistance.”

Eat well and exercise … your future mental health depends on it.

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