adenomas (Giovannucci et al., 1993b; Kahn et al., 1998). A dose-response relationship has been observed across several studies, and some evidence suggests that even moderate drinkers (those who consume one drink a day) are at higher risk of colorectal cancer than nondrinkers (World Cancer Research Fund and American Institute for Cancer Research, 1997).
The effects of alcohol may be exacerbated by low levels of folate (Freudenheim et al., 1991). In the Health Professionals Follow-Up Study, an increased risk of colon cancer was observed only among those current and past drinkers who consumed lower levels of methionine or folate in their diets (Giovannucci et al., 1995b). Because alcohol is an antagonist of folate-related methyl group metabolism, it may cause an imbalance in DNA methylation, which may then contribute to colorectal carcinogenesis.
Although a number of cohort studies have examined the association between alcohol consumption and lung cancer, few have adequately adjusted for the effects of smoking. Those that have adjusted adequately have yielded inconsistent findings. Four cohort studies have shown a positive association (Klatsky et al., 1981; Kvåle et al., 1983; Pollack et al., 1984; Potter et al., 1992), and four have yielded null results (Gordon and Kannel, 1984; Bandera et al., 1997; Woodson et al., 1999; Breslow et al., 2000).
Data on alcohol consumption in the United States indicate that the top 20 percent of drinkers consume more than 85 percent of all alcohol consumed (Greenfield and Rogers, 1999). Men and young adults ages 18 to 29 years are disproportionately represented among those with the highest alcohol consumption levels. The National Health Interview Survey (1998) indicates that at each age, the proportion of current drinkers is highest among non-Hispanic white men, followed by African-American men, and then Hispanic men (National Center for Health Statistics, 2000). Among women, the proportion of current drinkers is also highest among non-Hispanic white women at each age.
There is overwhelming evidence that lifestyle factors affect cancer risk. As detailed throughout this chapter, current epidemiological evidence links the major behavioral risk factors with several major cancers. Tobacco use causes cancers of the lung, oropharynx, larynx, esophagus, bladder, kidney, and pancreas and contributes to the risk of leukemia as well as cancers of the