The thing is, there are simply too many variables. Using your example of lecithin, there are numerous studies that show it is effective in improving/reversing

The thing is, there are simply too many variables. Using your example of lecithin, there are numerous studies that show it is effective in improving/reversing fatty liver disease. https://www.bcm.edu/news/lecithin-component-may-reduce-fatty-liver https://www.bcm.edu/news/lecithin-component-may-reduce-fatty... There have been other studies that establish a link between liver health and alzheimers, even that protein from the liver can cause Alzheimer's disease in the brain. https://www.sciencedaily.com/releases/2021/09/210914152531.htm https://www.sciencedaily.com/releases/2021/09/210914152531.h... That study aims to prove that high fat content in the liver could cause Azlheimer's. So indirectly, taking lecithin may help the brain, even though it doesn't cross the blood brain barrier! Too many variables.