**9.2.1 Physical activity**

Five percent of cardiovascular mortality rate is caused by low physical activity. 13% is the estimated value for CRC (Slattery & Potter, 2002). This is probably due to the combination of low physical activity, nutrition, lifestyle, and their cross-interactions. The mode of action of physical activity upon CRC is not clear, but decrease in inflammation and insulin levels is supposed. A middle intensive physical activity 3-4 times per week with 1.5 h duration is advisable. Increased physical activities, especially in men, reduce the risk for CRC with 40- 50% (Scottish Intercollegiate Guidelines Network. Management of Colorectal cancer. A national clinical guideline., 2003).

#### **9.2.2 Tobacco smoking**

Many authors consider CRC as tobacco-related, taking into account the duration of smoking. It is estimated that 12% of the cases of CRC are related to smoking (Courtney et al., 2004). The present study confirmed the role of tobacco smoking as a risk factor for CRP and CRC. The risk is elevated proportionally to the years of smoking. Tobacco smoking disrupts conjugation of glutathione, cytochromes and damages DNA (Pfohl-Leskowitcz et al, 1999). Inhalation of carcinogens from tobacco smoke could trigger microsatellite instability (Yang et al., 2000).
