Alan, until the cows come home of their own accord, wood turners will manage to perpetuate myth and rumour about the suitability of woods used in contact with food. To exacerbate this issue the supplies industry has cashed in by marketing food safe oils. This of course implies that all others are not food safe??!!
Yew and laburnum are the subject of many debates about the toxicity of wood, if you happen to have a long main, are followed by a man with a bucket and whose height is measured in hands, it is a bad idea to eat the foliage of either yew or laburnum, but there is no evidence to suggest that the interaction of food and the dried, seasoned, wood will cause the user to drop alarmingly dead. They are both beautiful timbers, and in the case of yew, has been used in the Middle Ages to make drinking vessels. There was a practice of seasoning yew by cutting it and then tethering it to the banks of a flowing river for a year to assist with the removal of the sap..
There is much seasonal movement in correctly dried holly timber, and this is a timber that I wouldn't use. Any wood used to make salt mills must be thoroughly seasoned as the salt will take up any moisture left in the wood and can cause the wood to contract further and seize the mechanism, apparently!
I have just picked up a billet of splayed holm oak which I am looking forward to making some mills from. I've made them from ash, elm, oak, yew, cherry, laburnum, robin is, apple, walnut, psalter beech, birch, and others.