Masturbation Sin or Natural?

I've been arguing at standpoint with this debate. My parents and grandparents claim it is natural, but 3 of my youth groups say it is a sin. This debate is tearing me apart for 3 weeks now! This poll is open for all backgrounds and both sides. This is why I placed this question in general society. If I chose health, natural act would win. If I chose spirituality, sin would win. I want to hear both sides duke it out.