I know this thread is old, but for those who visit this thread in the future, I'm just adding some info regarding the idea that a white tongue is caused by toxins.

Aajonus Vonderplaintz, stated in a lecture linked below from 1:25:40 to 1:26:37, that a white tongue is caused when toxins (particularly toxic metals) from the brain are excreted through the tongue, where then calcium binds with the toxins and creates the white layer on ones tongue. This ultimately neutralizes the toxins, to make it safe to ingest.     

https://youtu.be/tyCZywmiZLk?t=5140

I am curious as to why this phenomenon occurs, as it has occurred to me about a week into consuming a raw carnivore diet (including some coconut water and a few mouth fulls of squashed veg and fruit juice). Could this function of the body be some kind of soft detox, if true? This, along with others, is one of the symptoms I have experienced, thus far into this diet.