Table 5

Three-way interaction for NAT2 phenotype, CYP1A2 phenotype, and red meat preference

CYP1A2 Phenotypea
NAT2bDonenesscNdORe (95% CI)NAT2DonenessNOR (95% CI)
≤MedianRare/medium59.931.0≤MedianRare/medium65.911.0 (0.6–1.7)
≤MedianWell-done28.271.6 (0.8–3.1)≤MedianWell-done16.240.9 (0.4–1.8)
>MedianRare/medium56.801.0 (0.6–1.8)>MedianRare/medium70.941.1 (0.7–1.8)
>MedianWell-done22.340.8 (0.4–1.6)>MedianWell-done33.242.1 (1.0–4.2)
P for interactionf = 0.13
  • a As determined by the urinary ratio (17U + 17X):137X; median = 5.1.

  • b NAT2 phenotype as determined by the urinary ratio (AFMU:1X); median = 1.1.

  • c Rare/medium includes did not eat, rare, medium-rare, and medium. Well-done includes well-done and very well-done.

  • d Number of cases/number of controls.

  • e ORs (95% CIs) adjusted by unconditional logistic regression for age, sex, ethnicity, pack-years of cigarette smoking, number of cigarettes, cigars, and pipes smoked during the 2 weeks preceding the caffeine test, lifetime recreational physical activity, lifetime aspirin use, body mass index 5 years ago, years of schooling, and intakes of nonstarch polysaccharides from vegetables and calcium from foods and supplements.

  • f Based on the likelihood ratio test comparing the model with interactions with one containing only main effects for these three variables.