Here's the story as simply as I can give it to you. There's a diet, the Ketogenic diet, that has been found to stop epilepsy in many cases. It's still a bit controversial, but a lot of folks swear by it. In some separate research, it was found that the amount of altered states people have is a kind of spectrum. Only a few people never have them, and only a few people have them all the time.
Most people fall somewhere in the middle.
You don't have to be an epileptic to have these experiences. If altered states and epilepsy share a mechanism in common, then if you find that you're having a hard time staying 'grounded', then the ketogenic diet might just be the thing to help you out. The Ketogenic diet is a carefully calculated, high fat, low protein, virtually carbohydrate-free diet that is used for the treatment of Epilepsy. P.M.H. Atwater, who works with Near-Death Experiencers, and has had three such experiences herself, commented that the most grounding food she could find was Mcdonald's French fries, and many of the people she worked with agreed. French fries, being greasy, are specifically allowed in the Ketogenic diet.