Some forms of cancer are hereditary. I suppose that you view these people as "defectives" and should be sterilized or murdered, so that they don't breed....right?
Absolutely NO cancer is "preventable" through whatever you imagine is going to stave it off! Prostate cancer, if you are a male, is a cancer that you WILL get at some point in your life....if you live long enough.
Leukemia, in all of it's forms, hits without warning and no matter what one eats, exercises one does, WILL strike any age, any sex, any age.
Many people who have NEVER smoked, been around smokers, have lived and eaten well/whatever YOU might consider "correctly", get LUNG CANCER!
I can go on, but hope that these few examples have shamed you and put you in your place...in a corner, wearing a gigantic dunce cap!
And no onto heart disease and strokes.
These also run in families; at least the predisposition to it does. Yet there are many people who eat all the wrong thing, are fat, and never exercise at all, who NEVER have any heart problems at all!
Consider yourself BUTT-HURT in the extreme; you stupid, uneducated, sorry excuse for a human being.
Tony Snow comes to mind.
God, I miss him.