Highly Processed Foods Are Bad for Your Brain

May 29, 2024

Eating a diet containing lots of highly processed foods like chips, cookies and sodas may increase the risk of thinking and memory problems, according to a new report. It may also increase the risk of stroke. Eating foods that are unprocessed or minimally processed, on the other hand, may decrease the risk of cognitive problems and stroke.
Ultra-processed foods, which are designed to be convenient and tasty, account for more than half of the calories that Americans consume. They include most fast foods, sodas and packaged goods and are typically high in added sugars, refined carbohydrates, salt and fats, as well as synthetic flavoring agents and preservatives. They also tend to be low in protein and fiber. 
Examples of highly processed foods include many popular brands of packaged breads and crackers, soft drinks, breakfast cereals, sweetened yogurts, snack bars, ice cream, sausage, ketchup, mayonnaise and canned baked beans. “Low-fat” chips and snacks may be lower in oils but are typically still highly processed.
Unprocessed or minimally processed foods include meats such as simple cuts of beef, pork, chicken and fish, and vegetables and fruits. Whole grain breads or pastas are less processed than white bread or regular pasta.
“We found that increased consumption of ultra-processed foods was associated with a higher risk of both stroke and cognitive impairment,” said study author Dr. W. Taylor Kimberly of Massachusetts General Hospital in Boston. “Our findings show that the degree of food processing plays an important role in overall brain health,” 
For the study, researchers looked at 30,239 Americans aged 45 and older. None had a history of thinking or memory problems or stroke.
Participants filled out questionnaires about what they typically ate and drank. The researchers ranked their diets according to the kinds of foods they ate, from the least processed to the most processed. They followed participants for an average of 11 years.
By the end of the study, 768 people were diagnosed with cognitive impairment and 1,108 people had a stroke. After adjusting for age, sex, high blood pressure and other factors that could affect risk of dementia, researchers found a 10 percent increase in the amount of ultra-processed foods consumed was associated with a 16 percent higher risk of cognitive impairment, and an 8 percent increased risk of stroke. The association between ultra-processed foods and stroke was greatest among Black study participants.
Eating more unprocessed or minimally processed foods, on the other hand, was linked with a 12 percent lower risk of cognitive impairment, and a 9 percent decreased risk of stroke.
The study does not prove that eating ultra-processed foods causes memory and thinking problems and stroke; it only shows an association. And “more research is needed to confirm these results and to better understand which food or processing components contribute most to these effects,” Dr. Kimberly said.
But the findings add to a growing body of evidence showing that highly processed foods are bad for the brain. Eating highly processed fast foods and other junk foods, other studies have found, increases the chances of developing Alzheimer’s disease, the most common form of dementia overall. Eating a protein-rich, high fiber diet containing lean meats, seafood (not fried), whole fruits and vegetables, and heart-healthy fats like olive oil, on the other hand, may lower dementia risk.
And it may not take much. A study from 2022, for example, found that substituting 50 grams of unprocessed foods a day — equivalent to half an apple, a serving of corn, or a bowl of bran cereal — for the same amount of highly processed foods was associated with 3 percent decreased risk of dementia.
To cut down on processed food consumption, start by reading food labels. Many ultra-processed foods contain a long list of ingredients, including dyes, stabilizers and preservatives that may sound like something from a chemistry class. Also avoid foods with added sugars and sweeteners. In general, the fewer ingredients, the better.
By ALZinfo.org, The Alzheimer’s Information Site. Reviewed by Eric Schmidt, Ph.D., Fisher Center for Alzheimer’s Research Foundation at The Rockefeller University.
Sources: Varun M. Bhave, BA; Carol R. Oladele, PhD, MPH; Zsuzsanna Ament, PhD; et al: “Associations Between Ultra-Processed Food Consumption and Adverse Brain Health Outcomes.” Neurology, May 22, 2024
Peipei Gao, MS, and Zhendong Mei, PhD: “Food in Brain Health: Does Processing Level Matter?” (editorial). Neurology, May 22, 2024

Alzheimer's Articles