Cameron Diaz doesn't flush the toilet.

The 'My Sister's Keeper' actress does all she can to be environmentally friendly, and believes it is a waste of water to pull the chain every time she has relieved herself.

She said: "I do follow the, 'If it's yellow leave it mellow, if it's brown flush it down' saying. I believe in that 100 per cent.

"But there are a couple of rules. You can't go more than two or three times, if it's consecutive, if you're drinking a lot of water, without flushing. But if you have coffee or something, it's going down!"

The 36-year-old actress - who drives a Toyota Prius, a hybrid electric car - has been interested in green issues since she was a child, and credits her parents with making her environmentally aware.

She explained to US TV talk show host Jay Leno: "It's one of those things that is just a lifestyle choice. I was brought up that way so it's something that I automatically do. I'm rigged that way."