It takes a few years to work. Years ago I asked an ask-a-psychiatrist about it and he was fascinated and later I think did some research on it. I don't know what he came up with.

I worked at a camp for kids with special needs when I was in college and had a child on this diet. It was very hard to follow in an away-from-home setting and triggered a bunch of seizures for him. So I'd be somewhat afraid that any deviation from diet could trigger a major mood episode (because we did keep him as close to the diet as possible and I personally controlled what he ate b/c we decided having one person responsible for knowing the diet would be the most beneficial. But the required foods weren't always possible and so he had things off the diet and it didn't take much to start him seizing. (My superhero moment was that I was manic that summer and not sleeping. I was laying in bed half asleep and half annoyed that I was awake and the kids usually started getting up about 2 and heard a funny noise. I leaped down from my top bunk without using the ladder, ran to him and was there for his seizure before it really started. (It hurt to land though so not such a great superhero). Not that I could help much but at least I kept him from falling out of bed. The next day he had one and smacked his head and we had to sleep in the infirmary. From then on he was just glued to me for safety sake. I don't think he got to go back to camp which was sad. He was only 7 and I wonder about him a lot. He'd be in his late 20s now.