Single milkshake can impair brain blood flow, study finds
University of South Wales researchers say high-fat meals may affect the brain's ability to regulate blood flow, with older adults showing greater impairment.
A new study from the University of South Wales finds that consuming a milkshake rich in saturated fat can impair blood flow to the brain, potentially raising the risk of stroke and dementia. Researchers say that after a high-fat meal, blood fats rise and blood vessel walls stiffen, which can hinder blood flow and force the heart to work harder. The effect appears to peak about four hours after consumption. The study recruited 20 men aged 18 to 35 and 21 men aged 60 to 80, who were tested after drinking a milkshake researchers dubbed the brain bomb because its primary ingredient was heavy whipping cream. The shake contained 1,362 calories and 130 grams of fat.
In the experiment, researchers measured the performance of arteries linked to heart and brain health before and after consumption. The team said their findings align with prior work showing that a high-fat meal can impair the ability of the blood vessels to open or dilate, a function important for regulating blood flow and blood pressure. The impairment was observed in both younger and older participants, but the older group exhibited about a 10% greater reduction, suggesting that aging may heighten susceptibility to the brain- and heart-related effects of saturated fat intake. Marley and Bailey noted that the effects peak four hours after eating and that the brain’s capacity to buffer blood pressure is compromised after such meals. They also cited evidence that high-saturated-fat meals can raise free radicals and lower nitric oxide, a molecule that helps relax blood vessels and support oxygen and glucose delivery throughout the body. The authors emphasized that the American Heart Association recommends limiting saturated fat to less than 6% of total daily calories. For a 2,000-calorie daily diet, that translates to roughly 13 grams of saturated fat per day. One tablespoon of butter contains about 7 grams, and two slices of bacon add roughly 3 grams, illustrating how easily the limit can be exceeded. 
Experts also urged substitutions toward polyunsaturated fats—found in oily fish, walnuts, seeds, avocado and olive oil—given their association with reduced heart disease risk. Still, Marley and Bailey cautioned that their study did not determine how brains in women would respond to a saturated-fat meal, noting a crucial knowledge gap because women face a different risk profile for stroke and dementia later in life. The researchers expressed hope that the findings highlight the immediate and long-term importance of nutrition for brain health. “Our findings confirmed previous research that a high-fat meal impairs the ability of the blood vessels linked to heart health to open in both young and old participants,” they wrote. “This was more pronounced (by about 10%) in the older adults, suggesting that older brains may be more vulnerable to the effects of the meal.” They added, “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.” 