Why would I have pellagra symptoms if I take a vitamin B multi complex everyday, am I being scammed?

Dr berg says dry feet is due to a niacin or vitamin b3 deficiency so today I had 3 spoons of nutritional yeast but he said vitamin b3 deficiency comes slowly and you recover and get worse on a gradual basis.

Why would I have pellagra symptoms if I take a vitamin B multi complex everyday, am I being scammed?
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