One in three of the seven million cancer death worldwide is caused by nine potentially modifiable risk factors, according to a study from Harvard Medical School ( Lancet, November 19, 2005.) Being overweight causes your full fat cells to release chemicals that cause inflammation that can lead to cancer. Lack of fruit and vegetables deprives you of antioxidants that prevent cancer. Lack of exercise increases inflammation that causes cancer by the same mechanism as full fat cells . Smoking exposes you to nicotine that causes blood vessels to grow and nourish cancer cells. Excess alcohol dehydrates cells, which can cause cancer. Unprotected sex exposes you to cancer-causing viruses. Urban air pollution and indoor smoke from solid fuels expose you to carcinogens in the air, and contaminated injections expose you to viruses and other agents that cause cancer. You can improve your odds against cancer by avoiding overweight, eating lots of fruits and vegetables, exercising, avoiding smoking and alcohol, practicing safe sex, and avoiding indoor and outdoor air pollution whenever possible. Avoid injections unless they are necessary for health.