I know it sounds impossible but I swear it happened to me.
4/5 years ago, when I was in my early 30s, I started getting a few greys. Over the course of a couple of years they went from one grey hair to maybe 15/20.
Then I quit alcohol. Over the course of the following couple of years, all my greys disappeared. Now I am in my late 30s and I have zero grey hair. The only lifestyle change I made was quitting alcohol.
I am not sure how it is even possible but I am the living proof that this can somehow happen 