Enjoying a greasy takeaway might feel like a fun Friday night treat, but our recent study indicates that even one high-fat meal could disrupt blood flow to the brain, possibly elevating the risk of stroke and dementia.
Dietary fat plays a key role in our nutrition. It serves as a concentrated energy source, helps transport vitamins, and, when stored, provides protection to our organs while keeping us warm.
The fats in our diet can be categorized into saturated and unsaturated, which include both monounsaturated and polyunsaturated fats, based on their chemical structures.
But these fats affect our bodies differently.
For instance, it’s well-known that indulging in a meal rich in saturated fat—like a takeaway pizza—can negatively impact our cardiovascular health. This isn’t just limited to the heart, though.
The brain, with its limited energy reserves, depends heavily on a steady blood supply to deliver oxygen and glucose necessary for its proper functioning.
One way the body manages this supply is through “dynamic cerebral autoregulation,” a process that maintains stable blood flow to the brain despite daily fluctuations in blood pressure, like when we stand up or exercise. It’s comparable to having shock absorbers to keep our brain steady under pressure.
However, when this regulation falters, managing those blood pressure changes becomes trickier, which can result in episodes of inadequate or excessive blood flow to the brain.
Over time, such issues may heighten the risk for conditions like stroke and dementia.
How does diet affect this?
After consuming a high-saturated-fat meal, blood fat levels increase, peaking around four hours later. Meanwhile, blood vessels may stiffen, reducing their capacity to relax and expand, which limits blood flow.
However, the impact on the brain during this period and how well its blood supply holds up remains largely unclear.
To explore this, we engaged 20 young men aged 18 to 35 and 21 older men aged 60 to 80. We monitored the function of blood vessels associated with heart and brain health before and four hours after they consumed a high-saturated-fat meal.
We evaluated how well a blood vessel in the arm could dilate in response to increased blood flow as an indicator of heart health. This technique is called “flow-mediated dilatation.”
To assess how well brain blood vessels responded to blood pressure variations, participants performed body-weight squats while we used ultrasound to measure blood flow during both tests.
The meal was a milkshake dubbed “the brain bomb,” primarily made from heavy whipping cream, totaling 1,362 calories and 130 grams of fat—similar to a fast-food takeaway.
The results echoed previous findings, showing that a high-fat meal hampers the dilation ability of blood vessels linked to heart health in both younger and older participants, thereby diminishing the brain’s capacity to buffer blood pressure fluctuations.
This effect was more significant—about 10%—in older adults, suggesting they might be more susceptible to the negative impacts of such meals.
Although we didn’t specifically test the long-term consequences of a high-fat meal on mental performance, earlier studies have shown that such meals increase free radicals—damaging, unstable molecules—and decrease nitric oxide, which is essential for blood vessels to relax and transport oxygen and glucose.
This may clarify the reduced blood flow regulation we detected in our research.
This presents important clinical implications. While an occasional indulgence is unlikely to be detrimental on its own, our findings indicate that even a single fatty meal can have immediate effects on the body.
The study underscores the necessity of a diet low in saturated fat to safeguard both heart and brain health, particularly for older individuals who appear more affected by such meals and are already at greater risk for stroke and neurodegenerative diseases.
The NHS recommends that men limit their saturated fat intake to 30 grams daily, while women should aim for no more than 20 grams. Nonetheless, many of us often exceed these recommendations, especially during weekend takeaways or fast-food splurges.
Moreover, we likely spend a considerable amount of our waking hours in a post-meal state, known as “post-prandial lipaemia,” when fat levels are elevated and may pose a heightened risk.
Considerations
There’s still much to understand in this area.
Public health advice suggests replacing saturated fats with polyunsaturated ones, commonly found in oily fish, walnuts, and seeds, which are linked to improved heart and brain health over time.
However, it remains unclear how the brain reacts to a high-polyunsaturated-fat meal, or how women’s brains specifically respond to high-fat meals. This is an essential area of research since women face a higher risk of stroke and dementia as they age compared to men.
This study serves as a timely reminder that our diet influences both immediate and long-term health. When it comes to maintaining brain health, it seems that every meal practically counts.
