A large study published last summer in Neurology reported a link between consuming ultra-processed foods—such as soft drinks, potato chips and other salty snacks, deep-fried or packaged meats, bottled condiments, prepackaged sweets and breads, and flavored breakfast cereals—and a higher risk for dementia and Alzheimer's disease. For every 10 percent increase in ultra-processed foods consumed, the risk for Alzheimer's rose 14 percent; for dementia overall, it increased 25 percent, according to the study.

Researchers from Tianjin Medical University in China tracked the diet and health of 72,803 women and men from the United Kingdom, ages 55 and older, for a decade. Participants were divided into four groups based on how much ultra-processed food they ate. None had dementia at the start of the study, but nearly 43 percent more people in the highest group of ultra-processed food intake developed dementia than in the lowest group.

Those in the lowest group consumed an average of 225 grams of ultra-processed foods per day—by weight, approximately 9 percent of their total food consumption—while subjects in the highest group took in an average of 814 grams, or 28 percent of their daily diet. (For reference, one serving of pizza weighs about 150 grams.)

The study authors estimated that a 50-gram replacement of an ultra-processed food each day with a healthier, less-processed food—eating half an apple, a bowl of bran flakes, or a serving of corn instead of a chocolate bar, for instance—was associated with a 3 percent lower risk of dementia.

These results join others that show an association between ultra-processed foods and negative health effects such as obesity, high blood pressure, high cholesterol, cancer, heart disease, stroke, and earlier death. Scientists don't know exactly why such foods are bad for the brain but believe they may increase blood pressure and contribute to buildup of artherosclerotic plaque in arteries, says Linda Hershey, MD, PhD, FAAN, a retired professor of neurology at the University of Oklahoma College of Medicine. The Tianjin researchers suggested these foods might increase inflammation, which could fuel growth of tau protein tangles—a hallmark of Alzheimer's disease.

“It's impossible to derive cause and effect from observational studies,” says David Seres, MD, professor of medicine at the Institute for Human Nutrition at Columbia University in New York City. “But this study is potentially important. It's probably not a bad idea to avoid processed foods and eat those that look like they did when they came out of the ground or off the hoof as much as possible.”

Ultra-processed foods tend to be higher in added sugar, saturated fat, and salt, and lower in protein and fiber, than fresh or minimally processed foods. About 57 percent of the calories in the average American diet come from ultra-processed foods, according to a 2022 study published in the American Journal of Clinical Nutrition.

“The vitamins, minerals, phytochemicals, and healthy fats in fruit, vegetables, whole grains, legumes, nuts, and other foods work together in a healthy diet,” says nutrition researcher Maura Walker, PhD, assistant professor of health sciences at Boston University and co-author of an editorial published with the Neurology study. She advises people to eat more fresh fruits and vegetables, frozen produce without added sugar or sauce, and even canned produce if it is low in sodium and sugar.

You can also improve your diet by checking the nutrition panel on food packages. Foods with 5 percent or less of the daily value for sugar are considered low in sugar. Buy packaged breads and cereals only if the first ingredient listed is a whole grain.

Limit consumption of sweetened, diet, and prepackaged coffee or tea drinks, says Dr. Walker. (The American Heart Association recommends no more than 6 to 9 teaspoons of added sugar per day, from all sources.) Soft drinks and bottled juices can be unhealthy whether they contain added sugar or artificial sweetener. A 2017 Boston University study published in Stroke found that drinking artificially sweetened soft drinks was associated with an increased risk of stroke and dementia. The researchers noted that people who drank more artificially sweetened soft drinks were also more likely to have diabetes, which raises dementia risk.

How to Swap Out Ultra-Processed Foods

Breakfast
Buy cereals low in added sugar (read the labels), and eat fruit salad as a side instead of bacon or sausage.

Beverages
Drink unsweetened coffee or tea or plain or sparkling water (add a squeeze or slice of citrus fruit) instead of soda, premade tea, and fruit drinks.

Lunch Meat
Choose slices of lean pork, beef, or skinless chicken or turkey instead of deli meat.

Snacks
Munch on raw vegetables or air-popped popcorn seasoned with herbs instead of chips, crackers, and other salty foods.

Dinner
Grill, bake, or pan-sear fish or roast chicken instead of heating up prepackaged fish sticks or chicken nuggets. Make a salad or steam vegetables without sauce or cheese, or cook brown rice, bulgur, or barley instead of french fries, instant noodles, and packaged macaroni and cheese.

Dessert
Enjoy a bowl of berries, fruit salad, or an apple, banana, orange, peach, or other whole fruit instead of ice cream, cookies, candy, and packaged cake or other sweets.

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For alternatives to meals that contain ultra-processed foods, read Eat Fewer Processed Foods with these Healthy Swaps for recipes developed by chef and Natural Gourmet Institute graduate Linda Monastra.