Blood-brain barrier and food?

[Guest guest]

What exactly does it mean for a food to cross the blood-brain

barrier? I fight brain fog a lot of the time and have wondered what

this statement means, and what those foods are. From the statement,

I'm assuming there are foods that can't cross the blood-brain

barrier, why? Naturally, I'm curious what particular foods might

help you to be alert and sharp instead of being in a fog? Improving

my diet hasn't really helped much. There must be something else

that is causing my brain not to get the fuel it is needing. Any

ideas?

Robin