the physical and "spiritual" problems are so interconnected that an unhealthy diet is part of a bigger "spiritual" thing.
Agreed, although one of my close friends who took ayahuasca with me had a healthy diet (and had fasted for a day beforehand) yet somehow managed to purge for 20 minutes at the beginning of the journey. She was vegan, and mostly ate quinoa, avocadoes, cashews, fresh fruit, tea, and chocolate. Some of the troubles she came to aya to resolve got puked up...
Anecdotal such evidence may be, but I think it makes the point. I'm not really disagreeing with you, fractal, just saying that a good diet alone might not protect you from the Purge...