In April this year I had the worst migraine ever. So, I decided to try cutting diet coke out of my diet, and wow what a difference! The artificial sweetener in diet drinks is aspartame, which has a huge list of side effects and health problems that it can cause. 5 months later, I have cut aspartame out of my diet completely and I haven't had a migraine in 3 months (used to get 2-3 a month) and I generally feel healthier and happier. I wasn't even drinking that much coke so it just goes to show that you don't need much to have an effect. Also, it can take quite a few weeks to leave your system completely so giving up for a week or two isn't enough, you won't feel the benefits in that short time.
For more info, read this link or just google 'aspartame'
I'm not getting into a debate here about whether aspartame is safe or not, I don't know enough about it to state publicly either way. I can however say with complete honesty that I feel 100% better since I cut it out of my diet and I haven't had a migraine for 3 months.
That's all I need to know!