I've been in a highly respected choral group for over 20 years--have sung mostly in the Kennedy Center but also in Spoleto, Royal Albert Hall, Carnegie Hall, etc.    Always ignored this advice.   Yogurt is part of my diet--every day, if I can get it.   Regardless.

Never had a problem singing exactly on key.    If you have a good ear and concentrate on doing so, you can do it without difficulty.   Far more important to know at any given point what your note should sound like, especially in relation to other voices.