Thanks Sandy and all of you for your advice!
I think i wasn't not so clear with what i posted before. In fact, my husband was suffering from serious migraine since he was on Nilotinib 800mg. The migraine kept him more than 20 hours in the bed everyday. He couldn't move due to the headache, and became extremely sensible to light so he could only stay in bed for 20 hours in the dark, otherwise he would vomit. It wasn't a light headache that everyone could have. I understood 3 days was not enough to see the effect of Nilotinib, but 3 days without eating but staying in the dark vomitting, I don't think it is a reasonable side effect that one should accept.
We are actually on a trial of Nilotinib and one of the conditions of this trial is that when the patient got some serious side effects (level 2-3) for 3 times after taking the drug, they are allowed to lower the dose. We respect the rules and the decision of lowering the dose to 400mg once a day was a decision made together with our doctor. Now he is under the half dose and the side effects are gone.
About cutting grapefruit and other dieting rules, we have very clear guidelines from our doctor and we follow all the them strictly. We 've been having healthy diet since the first day we were on glivec.
We were told by our doctor that Nilotinib 400mg could be still as effective as Glivec 400mg, that is also why Nilotinib 400mg is one of the options in the trial. However, due to the privacy problem, we can't know if there is any 'real case' that Nilotinib half dose is working well for patients. That's why I was seeking patients with the similar situation like us.
Anyway, thanks a lot for all of your advice. We will fight hard and so do you! 
Fibi