I tell people, "Grow some cannabis. Get off your xxx addiction. (usually opiates or alcohol..)
or
"Find a farmer in your area, negotiate a medicinal price and ask for the leaves and flowers usually thrown away; this makes the best medicine to cure your mother's cancer (of any type really)."

Response: "But I can't, it's illegal in my country, yaha yada."

This is where I get stressed, and my voice changes a bit:

"Then do it anyway, and work to get your laws changed. It's called Civil Disobedience; there is a proud tradition. Besides, you are going to be very discreet and not get caught."