Not sure about blacks, maybe because of higher T causing more oily secretions?
For curries it's definitely diet. In the past, I could smell curry on my curry friends' jackets.
I've been eating a lot of kimchi lately because I heard it can improve your gut health, since I have some GI issues. But now my breath is a little bit putrid and smells like garlic all the time no matter how much I brush.
You are what you eat.