On current evidence exercise is clearly the best method for increasing useful everyday cognitive functioning.
This is the conclusion of a piece over on PsyBlog, Which Cognitive Enhancers Really Work: Brain Training, Drugs, Vitamins, Meditation or Exercise?
Ultimately, there is little conclusive scientific evidence to support the oft-claimed beneficial effects of brain training, drugs, vitamins or meditation on cognition.
Of course, that doesn’t mean they’re not worth doing.
What I take out of this is that exercise needs to be part of your daily routine.