Fat that's bad for the heart, brain
Saturated fat, the same "bad" fat that contributes to heart disease, is also bad for your brain. A Harvard study of 6,000 women published in Annals of Neurology found that those who ate the most saturated fat had the worst memory and thinking ability over time. Total fat consumed did not affect brain function, but the type of fat did. Those who ate the most saturated fats from foods such as red meat and butter performed the worst on cognitive tests. Those who ate the most monounsaturated fats, found in olive oil and nuts, did the best. Polyunsaturated fats and trans fats had no effect on brain health. The researchers reasoned that higher levels of inflammation created by saturated fat consumption might damage the arteries in the brain, leading to cognitive dysfunction.