The ketogenic diet can be high in a plant anti-nutrient known as oxalate.
Cooking, ‘activating’ (as the hippies call it), fermenting, pre-digesting food technology has long helped humans cope with the potential toxins in plant foods such as lectins.
Unfortunately oxalates are resilient and resist a lot of that detoxification preparation.
This thread needs some clarification on coffee in regard to oxalates.
Still, there are two solid scientific reasons to believe that coffee is very low in oxalate. The first is that all reputable testing to date has demonstrated that coffee is low in oxalate . The second is the real-world experience of low-oxalate dieters who have maintained a daily coffee habit with health benefits and without signs of oxalate-related symptoms. Other beverages, including hot chocolate, black tea, and green tea, have consistently been found to be high in oxalate and tend to trigger oxalate-related effects (the effects are variable—e.g. night-time irritable bladder)… I have a suspicion that the rumor about coffee being high oxalate originated in confusing reports on the oxalate content of instant coffee powder, which led to misinterpretation of the results. Instant coffee is indeed very high if you eat a whole cup of the undiluted powder.