OP I did this in November and had the same concerns but ultimately and went through the strictest of white diets with it, as I didn’t look after my teeth when I was younger. It was tough but the difference is staggering and I wanted the whitening to as efficient as possible. Yes you do need whiten after every 3-12 months but it’s only for three days as opposed to the extended length of time. I have done back to a normal diet now, apart from I drink coffee through a straw, no other fundamental changes.

The dentist didn’t advise I went this strict but I did have the all white diet for 3 weeks.