Eating greater quantities of red meat may increase risk of dementia

Red meat consumption is an established risk factor for chronic conditions, including cardiovascular disease and type 2 diabetes. A new study by investigators from Mass General Brigham, Harvard T.H. Chan School of Public Health, and the Broad Institute of MIT and Harvard found that eating greater quantities of red meat, especially in processed forms, increased risk for dementia, too. Results, published online on January 15, 2025, in Neurology^®, the medical journal of the American Academy of Neurology, highlight that replacing processed red meat with protein sources like nuts and legumes or fish may decrease dementia risk by approximately 20 percent.

"Dietary guidelines tend to focus on reducing risks of chronic conditions like heart disease and diabetes, while cognitive health is less frequently discussed, despite being linked to these diseases," said corresponding author Daniel Wang, MD, ScD, of the Channing Division of Network Medicine at Brigham and Women's Hospital, a founding member of the Mass General Brigham healthcare system.

Wang is also an associate member at the Broad Institute and an assistant professor in the Department of Nutrition at Harvard Chan School. "We hope our results encourage greater consideration of the connection between diet and brain health."

As the U.S. population ages, dementia represents a growing challenge for patients and families. Among 133,771 individuals included in this study with an average age of 49 years at baseline, 11,173 were diagnosed with dementia up to 43 years later. Data were drawn from the Nurses' Health Study (NHS) and Health Professionals Follow-Up Study (HPFS), which prospectively study thousands of participants' health and lifestyles, which may influence risk of chronic diseases like dementia. The studies include decades of detailed health information, including participants' typical diets, which they update every 2 to 4 years.

A typical serving of red meat is 3 ounces - approximately the size of a bar of soap. Those eating a daily average of one-quarter or more of a serving of processed red meats (roughly two slices of bacon, one and half slices of bologna, or a hot dog), compared to those consuming a minimal amount, (less than one-tenth a serving each day) had a 13 percent higher risk of developing dementia, adjusting for numerous clinical, demographic and lifestyle factors such as socioeconomic status and family history of dementia.

The researchers measured objective cognitive function using standard cognitive assessments. They found that this measure was also worse among those with greater processed meat consumption, with cognitive aging accelerated by approximately 1.6 years per average daily serving.

The researchers also examined self-reported subjective cognitive decline (SCD), which may precede markers of cognitive decline on standard evaluations. A greater risk of SCD was associated with consuming either processed or unprocessed meats (like beef, pork and hamburger). SCD risk increased by 14 percent for those eating one-quarter or more servings of processed meat daily compared to the minimal-consumption group, and by 16 percent for those eating one or more daily servings of unprocessed meat compared to those eating less than half a serving.

The researchers are continuing to explore factors linking red meat with dementia risk, especially those involving the gut microbiome. Trimethylamine N-oxide (TMAO), a product of the bacteria-mediated breakdown of meat, may increase cognitive dysfunction due to its effects on the aggregation of amyloid and tau, proteins involved in Alzheimer's disease, but research is limited. The saturated fat and salt content of red meat may also impair brain cells' health.

Large, long-term cohort studies are essential for investigating conditions like dementia, which can develop over decades. We are continuing to piece together this story to understand the mechanisms causing dementia and cognitive decline."

Daniel Wang, MD, ScD, of the Channing Division of Network Medicine, Brigham and Women's Hospital