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DRI DIETARY REFERENCE INTAKES FOR Vitamin C, Vitamin E, Selenium, and Carotenoids
Many investigators have reported that those who smoke, on average, have lower plasma carotenoid concentrations compared to individuals that don't smoke (Brady et al., 1996; Chow et al., 1986; Comstock et al., 1988; Fukao et al., 1996; Herbeth et al., 1990; Margetts and Jackson, 1996; Pamuk et al., 1994; Stryker et al., 1988; Witter et al., 1982). The greater the intensity of smoking (cigarettes per day), the greater is the decrease in serum carotenoid concentrations. Fukao et al. (1996) studied 1,902 Japanese men in a cohort study and showed a dose-dependent decline in geometric mean serum β-carotene with greater smoking intensity (Table 8-5).
While smokers ingest less β-carotene than nonsmokers, it is unclear at present whether or not the lower serum concentrations seen can be fully explained by the reduced β-carotene intakes of smokers, as discussed recently by Brady et al. (1996). Many studies find differences in serum carotenoid concentrations even after adjusting for intake. However, because dietary intake is necessarily measured with some error, it is unclear whether full adjustment is possible. Tobacco smoke is known to be highly oxidative, and the gas phase of tobacco smoke has been shown to destroy β-carotene and other carotenoids in in vitro studies of human plasma (Handelman et al., 1996). As demonstrated recently by Baker et al. (1999), both smoke and gas-phase smoke oxidize β-carotene to carbonyls, epoxides, and nitro derivatives. Thus, it is possible that the smoke oxidatively degrades β-carotene in vivo and thus contributes to the reduction in circulating levels.
TABLE 8-5 Serum β-Carotene in Men in Relation to Smoking