Rolling Stones song...

Ok a friend of mine and I have had a long standing debate over what the lyrics of "Brown Sugar" mean. Is it about black women, heroin or both?

Lyrics:
Gold coast slave ship bound for cotton fields,
Sold in a market down in New Orleans.
Scarred old slaver know he's doin' alright.
Hear him whip the women just around midnight.
Ah Brown Sugar how come you taste so good
(A - ha) Brown Sugar, just like a young girl should
A - huh.

Drums beating, cold English blood runs hot,
Lady of the house wond'rin where it's gonna stop.
House boy knows that he's doin' alright.
You should a heard him just around midnight.
Ah Brown Sugar how come you taste so good
(A - ha) Brown Sugar, just like a black girl should
A - huh.

I bet your mama was a tent show queen, and all her boy
Friends were sweet sixteen.
I'm no schoolboy but I know what I like,
You should have heard me just around midnight.

Ah Brown Sugar how come you taste so good
(A - ha) Brown Sugar, just like a young girl should.

I said yeah, I said yeah, I said yeah, I said
Oh just like a, just like a black girl should.

I said yeah, I said yeah, I said yeah, I said
Oh just like, just like a black girl should.