I learned the hard way that the oats and cashew nuts Ted loved with a passion were partly responsible for his developing oxalate crystals when he was about 5 years old. He first blocked before he was 1 year old and they diagnosed struvite crystals. Unfortunately, the acidified foods he was put on afterwards, plus the oats and nuts, gave him the other kind of crystals. A little would have been okay, but he would tear into the bags if they weren't in the fridge and gorge himself.