Even foods that are good for your health may have some properties that make them less than ideal. And some things that you eat are just plain bad for you. Lectins are often cited as a property in foods that you should avoid.
DS-Lite is an IPv6 migration technology, where the access network of the service provider is running IPv6.
These will play on any original DS or DS Lite without enhancements, but will only play on the same region's DSi or 3DS. I don't think this is a complete list and I couldn't find an official list of DSi region-locked DS games, but chances are that any games on this list won't work on a different region's DSi or 3DS.