Differences in Nicotine Metabolism

Differences In Nicotine Metabolism May Explain Ethnic Variations In Lung Cancer Rates

January 15, 2002 (Journal of the National Cancer Institute)

Chinese-Americans take in less nicotine per cigarette than whites and Latinos, allowing Chinese-American smokers to smoke fewer cigarettes than their ethnic counterparts to achieve the same nicotine-related effects, a new study suggests.

These findings may explain why Chinese-Americans have a lower rate of lung cancer than other ethnic groups, conclude Neal L. Benowitz, M.D., and colleagues at the University of California at San Francisco. Their results appear in the Jan. 16 issue of the Journal of the National Cancer Institute.

For years, scientists have puzzled over the impact of ethnicity on smoking behavior and risk of lung cancer. In 1998, Benowitz and his colleagues reported that African-Americans take in more nicotine per cigarette than whites, which may explain why African-Americans have a higher incidence of lung cancer.

The authors suggested that differences in intake of toxins from cigarette smoke may account for some or most of the ethnic variation in lung cancer risk.

In the new study, the authors analyzed nicotine intake per cigarette and nicotine metabolism among 37 Chinese-American, 40 Latino, and 54 white volunteers. All 131 participants were from the San Francisco Bay area and were healthy smokers. The ethnic groups differed in age, average daily cigarette consumption, type of cigarette smoked, and duration of smoking; however, the number of cigarettes they smoked per day reflected national averages of cigarette consumption for each ethnic group.

Each participant received an infusion of deuterium-labeled nicotine and cotinine, a byproduct of nicotine metabolism. The authors then estimated each ethnic group's daily intake of nicotine and the rate of nicotine metabolism. The authors found that Chinese-Americans took in statistically significantly less nicotine per cigarette than whites or Latinos. Chinese-American smokers also metabolized nicotine 35% more slowly than white or Latino smokers.

Finally, the authors observed a statistically significant correlation between the rate of nicotine metabolism and the intake of nicotine from cigarette smoke. The authors note that this correlation is consistent with the hypothesis that slow nicotine metabolism may contribute to the lower nicotine intake they observed in Chinese-American smokers.

In contrast to Chinese-American smokers, Latino smokers took in similar amounts of nicotine per cigarette and appeared to metabolize nicotine at a similar rate as white smokers. Nevertheless, the authors note that Latinos smoke fewer cigarettes on average and have a lower incidence of lung cancer. This phenomenon may be related to cultural differences, they say.

The authors conclude that understanding the rate of metabolism among different ethnic groups may be important in choosing optimal doses of the nicotine medications used to help smokers stop smoking.

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