A greasy burger and fries might seem like a harmless treat, but new research indicates that even one high-fat meal could impair blood flow to the brain, potentially raising the risk of stroke and dementia.
Dietary fat is essential, providing energy, aiding vitamin transport, and protecting organs when stored. It comes in two main types: saturated and unsaturated (monounsaturated and polyunsaturated), distinguished by their chemical makeup. However, their effects differ.
Saturated fats, found in indulgent meals like a takeaway pizza, are known to harm blood vessels and heart health, with impacts extending beyond the cardiovascular system.
The brain, with limited energy reserves, relies on a steady blood supply of oxygen and glucose. This is maintained through “dynamic cerebral autoregulation,” a process that stabilizes blood flow despite daily blood pressure changes, such as during exercise or standing. When impaired, these fluctuations can lead to inadequate or excessive blood reaching the brain, heightening risks of stroke and dementia over time.
Researchers, addressing this issue for the first time, studied 20 men aged 18-35 and 21 men aged 60-80. They measured vascular health before and four hours after a high-saturated-fat meal — a 1,362-calorie milkshake dubbed “the brain bomb,” made with heavy whipping cream and containing 130g of fat, mimicking a fast-food load. Tests included “flow-mediated dilatation” to assess arm vessel response and ultrasound during squats to evaluate brain blood flow regulation.
Results showed the meal reduced vessel flexibility linked to heart health in both age groups, with a more significant impact — about 10% greater — on older adults. This suggests older brains may be more susceptible. While long-term mental effects weren’t tested, prior research by the team found that high-fat meals increase free radicals and decrease nitric oxide, which may explain the observed blood flow issues.
“This has important clinical implications,” the researchers noted in an article in The Conversation. “While an occasional takeaway is unlikely to cause harm on its own, our results suggest that even one fatty meal has an immediate effect on the body.”
The study underscores the need for a low-saturated-fat diet to protect both heart and brain, especially for older adults at higher risk of stroke and neurodegenerative diseases. The National Health Service in the United Kingdom advises men to limit saturated fat to 30g daily and women to 20g, though many exceed this during weekend indulgences. This post-meal state, known as “post-prandial lipaemia,” may pose ongoing risks.
Further research is needed, including how polyunsaturated fats (found in oily fish, walnuts, and seeds) affect the brain and how women’s brains respond, given their higher stroke and dementia risk later in life.
“Our study offers a timely reminder that diet doesn’t just shape our long-term health. It also affects our body and brain in real time,” the researchers concluded. “And as we’re learning, when it comes to protecting brain health, every meal may count.”