I've been getting leg cramps lately. They're painful and annoying.

What can I eat or are there any supplements I can safely take in pregnancy to avoid these?

I'm already getting lots of calcium (mostly milk) and eating a balanced diet with lots of fruit and veg. I don't know what I'm missing, but I'm guessing I'm missing something in my diet and would like to make up the lack to make those cramps go away.

Any suggestions?