tant risk factor for colon cancer. An increasing number of epidemiological studies have found that the consumption of large amounts of sugar and foods with a high glycemic index is associated with an increased risk of colon cancer (Giovannucci, 1995b). On the basis of this growing evidence relating insulin, glycemic load, and colon cancer risk, further research is needed to determine if the insulin pathway might also contribute to other major malignancies.
The proportion of adults consuming the recommended five servings of fruits and vegetables a day has been estimated to be no more than 32 percent (Krebs-Smith et al., 1995a; Krebs-Smith et al., 1995b; Thompson et al., 1999; Li et al., 2000). Although these estimates are clearly low for the entire population, there is also considerable variation across subgroups defined by sex, race or ethnicity, education, and income. The levels of fruit and vegetable consumption are lower among men than among women (Subar et al., 1995; Kamimoto et al., 1999). One study showed that the level of fruit and vegetable consumption was lowest among Hispanics (Thompson et al., 1999), another found higher levels of consumption among whites than African Americans ages 55 and older (Kamimoto et al., 1999), and other studies have found lower levels of consumption of fruits and vegetables among individuals with lower incomes and lower levels of educational attainment (Subar et al., 1995; Thompson et al., 1999).
Although the level of consumption of red meat has decreased substantially in the population as a whole (U.S. Department of Agriculture, 1999), lower-income households have experienced less of a reduction than higher-income households (Interagency Board for Nutrition Monitoring and Related Research, 1993). In general, dietary trends in the last 60 years in the United States have shown a complex relationship with social class. Among those with higher socioeconomic status, diets have improved in regards to cancer and heart disease risk, whereas among those at lower socioeconomic classes, diets have worsened in the last half of the 20th century (Popkin et al., 1996).
Alcohol consumption has both beneficial and harmful effects on health. A U-shaped relationship between mortality and consumption of alcohol was described as early as 1926 (Pearl, 1926). A number of studies since then have shown that persons who drink heavily have higher rates of death from certain types of acute death, such as poisoning (Anderson, 1995), injuries (Andreasson et al., 1988; CDC, 1995), violence (Andreasson et al., 1988), and suicide (Andreasson et al., 1988), whereas the long-term use of alcohol increases the risk of death from cirrhosis (Norton et al., 1987),