I too cannot stop this unwanted trash coming into my email.
My Dr wanted me to look up the South beach diet, so I did and they asked a bunch of questions before they let you in. It was not the official website for South Beach Diet by the way.
Well after that my email was swamped with all this Junk mail I did not ask for any info either. and they neversaid they were giving all these solicitors my email addy.
How can I stop them? They have no unsubscribe on any pages and they do not respond to my emails send on their contact addy.
This is greatly affecting my work and it doesnt help me having spam filters and they being sent to my junk mail because I cannot just delete my Junk mail. I have to delete one at a time due to sometimes The Wanted emails for our business goes in junk if it doenst know the clients addy.