A lot of experts say for prolong fasting you need as minimum, Magnesium, Potassium (Cream of Tartar), sodium (salt), and if you are not getting any sun than Vitamin D. Some supplement with Zinc & Vitamin C.
With 18:6, short fasts, I’ve been told it’s not an issue. Multi-vitamins, Green powders etc…
Depends on individual health conditions & medications too.