As Seth Roberts, I believe that brain function is more sensitive to the environment than the other body's organs; thus it's easier measure the impact of nutrition and lifestyle changes by measure the impact on brain function. The brain is the canary in a coal mine, making possible to detect early the effects of changes in someone's lifestyle.
I did want replicate the arithmetic speed test to measure brain function, used by Seth Roberts in various self-experiments (removal of mercury amalgams, ingestion of flaxseed oil, ingestion of butter), but I don't wanted to use R for it. Then, I implemented a similar algorithm in Python, with a desktop interface. It can be downloaded here. This is a rough version, developed on my lunch time yesterday and today, but it just works fine, saving the result of the tests in a SQLite database file, that can be accessed for analysis purposes (this version don't have the 'view results' function implemented yet, but i'm going to implement it in the next version).
To use the Test of arithmetic speed, download it and execute the file 'arithmeticspeed.py'. You need the Python interpreter (2.6 or later) to run it.
I'll use it to measure brain function changes and evaluate my changes in lifestyle and nutrition, and so can you!