You shouldn't be down voted. This is generally good advice. Human nutrition is still poorly understood and there is huge variation between individuals. The best that most of us can do is run our own n=1 experiments and determine empirically what seems to give the best results.
Obviously there's no way to conduct a high quality controlled experiment and eliminate bias. But you can play around with adding or removing certain foods from your diet. Look for correlations with how you subjectively feel, and objectively perform. You might find some effects that are large enough to be significant even with n=1. Or not.
