 When you read articles like this in Alzheimer's disease journals about how eating more berries may reduce cognitive decline in the elderly, they're talking about observational studies like this, where berry intake appeared to delay cognitive aging by up to two and a half years in the Harvard Nurses' Health study, or the intake of nuts, appearing to delay brain aging by two years. They're just talking about associations, meaning berry eaters and nut eaters tend to have better brain function as they age after trying to control for a bunch of other lifestyle factors. But you don't know if it's caused an effect until you put it to the test. Thankfully, we now have a growing number of interventional studies that have done just that, randomized, controlled trials where people eat berries or nuts, and you can prove it, actually show improvements in cognitive performance, raising the berry-nutty idea that we may be able to forestall or reverse the effects of neurodegeneration in aging with food. For example, this study and the effects of walnut consumption on cognitive performance. College students split up into groups doing two months of walnuts, followed by two months of placebo, or vice versa, and then they switch. How do you make a placebo nut? They baked it in. They gave people banana bread, with or without nuts. Same ingredients, just one with walnuts. And those on nuts showed a significant improvement in inference capacity, the ability to accurately draw conclusions from a set of facts. In other words, kind of critical thinking. And so on a practical level, maybe students or young professionals in fields that involve a great deal of critical thinking or decision-making could possibly benefit and gain a slight advantage through regular consumption of walnuts. Or this berry study, where they randomized folks to some crazy berry smoothie with blueberries, black currants, elderberries, lingonberries, strawberries, and a tomato. And not only did their bad cholesterol drop about 10 points, they performed better on short-term memory tests. So good for the heart, good for the brain, and not just better on like pencil and paper tests, but real-world applications. Give people concord grape juice versus some fake grape-kool-aid type placebo, and you can get improved performance, unlike everyday tasks, like quicker response times in driving tests. Why not just give people concord grapes instead of juice? Well then it's harder to create a placebo, and of course the study was paid for by welches. Okay, fruit and nuts. What about vegetables? Consumers of cruciferous vegetables like cabbage, cauliflower, kale, collards, broccoli, and brussel sprouts have been found to perform better in several cognitive tests than non-users. In terms of cognitive decline with aging, women consuming the most green leafies did better, effectively slowing brain aging a year or two, and not just cruciferous, but other dark green leafies like spinach. So maybe it's the nitrates. As we age, our cerebral blood flow drops the amount of blood flowing through our brain, which may be due to an age-related decrease in the production of nitric oxide, the open sesame molecule that dilates our blood vessels and is boosted by the consumption of nitrate-rich vegetables. This reduction in blood flow to the brain may be a major risk factor for the impairment of cognitive function and the development of neurodegenerative diseases such as dementia. We know nitrate-rich vegetables like leafy greens and beets can improve physiological performance like beet juice does for athletes, but what about cognitive performance? We'll find out next.