Liu is a famous old Chinese doctor in Shanghai. He likes to treat lung cancer with watercress.

Recently, British scientists found that eating nearly 60 grams of watercress every day can prevent lung cancer. People who smoke more than 20 cigarettes every day should eat nearly 180 grams of watercress every day. The Sunday Times claimed that its anti-cancer effect benefited from a substance called Petit. The Norich Food Research Institute has been conducting experiments to extract this substance.