Our brains are primarily comprised of fat, so you could say we're all fatheads... which explains why the type of fat we consume has an enormous effect on how well our brains work in later life - what's called "cognitive function" or "cognitive decline".
A recent study published in the journal Diabetes Care (32:635-640, 2009) found that elderly diabetic women who consumed more trans-fat (partially-hydrogenated oils) and saturated fat in their younger years were significantly more likely to experience cognitive decline when compared to elderly women who consumed the lowest levels of these fats.
One of the reasons this makes sense is because trans-fat and saturated fat increase LDL (bad) cholesterol, which contributes to increased plaque formation. The more plaque in our arteries, the lower the oxygen supply to our brain, since plaque limits blood circulation (blood carries oxygen). When brain cells don't receive adequate oxygen over time they begin to die, and that ultimately causes "cognitive decline".
On the flip side, good fats, like Omega-3 fatty acid and monousaturated fat, improve circulation and therefore, oxygen delivery to the brain.
So where do all these fats come from? Trans-fat is mainly found in processed foods; saturated fat mainly comes from foods of animal origin: meats, dairy products, and eggs; Omega-3 and monounsaturated fat are found throughout unprocessed plant foods: fruit, vegetables, whole grains and legumes (beans, lentils, peas, nuts and seeds).
So should we all expect to experience serious memory loss as we age? Absolutely not. How we eat now determines the health of our brain later. And if you want to be truly inspired to take care of your brain, make a trip to a rest home soon.