Study: Bacon, processed meats may increase risk of dementia

People who eat a diet heavy in processed meats like bacon and sausage may be at higher risk for dementia, while those who take their protein instead from nuts and legumes may lower their risk, according to a study released Wednesday.

Tracking the reported dietary habits and health outcomes of more than 130,000 participants from two large, long term health studies, researchers found that people who ate one-quarter or more servings of processed meat daily had a 14% higher risk of dementia than those who ate less than one-tenth of a serving daily. A serving was defined as two slices of bacon, one hot dog, or two ounces of sausage, salami or processed meat sandwiches.

Participants who did not eat processed meat, substituting nuts and legumes, had a 20% lower risk of developing dementia.

Researchers also found links between higher processed meat intake and accelerated aging in cognition and verbal memory. To test cognitive function in a subset of 17,458 study participants, researchers did telephone interviews, using a cognitive test commonly used for seniors. That test found that for each added reported daily serving of processed meat, there was an extra 1.61 years of cognitive aging for global cognition and 1.69 years of cognitive aging for verbal memory.

Global cognition is a composite measure of function including language, executive function and processing; verbal memory is the ability to recall and understand words and sentences.

Researchers did not uncover a significant association between dementia and eating unprocessed meat, such as hamburger, steak or pork chops.

The study by Harvard T.H. Chan School of Public Health researchers and others was scheduled to be presented at the Alzheimer's Association International Conference in Philadelphia.

“This is very good evidence that processed meat intake impacts brain health,” though the biology is not well understood, said Puja Agarwal, a nutritional epidemiologist at Rush University Medical Center in Chicago who was not affiliated with the study. High cholesterol, high blood sugar and other conditions that may follow from a diet high in processed foods “all trigger different mechanisms that may impact the central nervous system at some level,” Agarwal said.

A 2021 editorial in the American Journal of Clinical Nutrition noted processed meats’ high contents of sodium, saturated fat, nitrites and other harmful compounds “that increase oxidative stress and inflammation, which are mechanisms linked to the development of dementia.”

Dr. Fernando Gomez-Pinilla, professor of neurosurgery and integrative biology and physiology at UCLA Health, the hospital system of the University of California, Los Angeles, who was not affiliated with the study, said much of its value stemmed from its duration — as long as 43 years, for some participants. “When we are talking about diet, the most important thing is long term effects, not just what happened in one day, one week,” he said. Diet can moderate but not eliminate risk of dementia, he added.

Earlier studies have shown associations between diet and cognitive functioning. A 2023 study presented at the Alzheimer's Association International Conference linked diets heavy in ultra-processed foods to cognitive decline in middle-aged and older adults. That study tracked eating habits and cognitive test performance of 11,000 Brazilians over eight years and found a 28% faster performance decline for those who consumed more than a fifth of their daily calories in ultra-processed foods. Ultra-processed foods were defined as containing processed food substances such as oils, fats, sugars and starch with little or no whole foods.

Studies also have associated healthy eating with cognitive benefits, but more research is needed to determine if diet can prevent or delay Alzheimer’s or age-related cognitive decline, according to the National Institute on Aging.

Some of those studies have shown that the Mediterranean and MIND diets — both feature vegetables, fruits, whole grains, olive oil, beans and fish — are associated with a lower risk for dementia compared to a typical Western-style diet containing more red meat, saturated fats and sugar, according to the institute. But a recent clinical trial of older adults with a family history of dementia showed the MIND diet yielded only small improvements in cognition.

Registered dietitians said the study was not grounds for total bacon abstinence, a recommendation they said patients were unlikely to follow anyway.

“If it’s once in a while, no problem,” said Imran Syed, a registered dietitian at Northwell Health’s North Shore University Hospital. Moderation can be difficult when delis, for example, keep “refrigerators packed with cured meats,” which can be priced affordably because of their long shelf life. Consumers are better off buying meat “as fresh as possible,” he said.

Angel Planells, a Seattle-based registered dietitian nutritionist and spokesman for the Academy of Nutrition and Dietetics, a trade group for nutrition professionals, said the study highlighted the importance of healthy eating among a constellation of other possible factors for dementia, including genetics, sleep and exercise.

“This is not earth-shattering research," he said. "But the more wholesome people eat, it puts you on a better trajectory for a lot of things."