So essentially, the most beneficial course here is getting into healthy habits and pursuing loss prevention. I haven't seen much evidence at all that otherwise well nurished and healthy people can raise their actual intelligence, but there seems to be a lot of things which can effectively reduce it, both short term and long. Removing or mitigating these can get folks closer to their potential. I think this has a lot of applications for people who worry about this. Like I've read studies quantifying I.Q loss per day of losing just 1 hour of sleep a night. After a few days parts of cognition can be effected heavily.