Walnuts are probably the best, but peanuts and cashews are fine too. They have the 'right' kind of fat in them, but you do need to avoid having too much salt and they are also high in calories. Ialso read recently that almonds are good for you:
http://www.dailymail.co.uk/health/a...nt-diabetes-heart-disease-say-scientists.html
According to my friend at work, her father, who has type 2 diabetes, eats 5 almonds a day doused in lemon juice and it helps to control his levels. She says this is quite a traditional Asian home remedy for diabetics. I've not tried it myself yet though.