Person:

Le, Ngoan

Background: Heterocyclic amines (HCAs) in cooked meats may play a role in colorectal cancer (CRC) development. Objectives: We aimed to prospectively examine the association between estimated intakes of HCAs and meat-derived mutagenicity (MDM) in two cohorts of health professionals, the Health Professionals Follow-up Study (HPFS) and the Nurses’ Health Study (NHS). Methods: In 29,615 men and 65,875 women, intake of the HCAs 2-amino-3,8-dimethylimidazo(4,5-j)quinoxaline (MeIQx), 2-amino-1-methyl-6-phenylimidazo(4,5-b)pyridine (PhIP), 2-amino-3,4,8-trimethylimidazo(4,5-f)quinoxaline (DiMeIQx), and MDM was estimated using a 1996 cooking questionnaire, the 1994 food frequency questionnaire, and an online database. Cox proportional hazards models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) and to adjust for potential confounders. Estimates for both cohorts were pooled using random-effects meta-analysis. Results: Between 1996 and 2010, 418 male and 790 female CRC cases were identified. Meat mutagen intake was not statistically significantly associated with risk of CRC [highest vs. lowest quintile, pooled HR (95% CI) for MeIQx: 1.12 (0.93, 1.34), p for trend 0.23; PhIP: 1.10 (0.90, 1.33), p for trend 0.35; MDM: 1.03 (0.86, 1.24), p for trend 0.75] or subtypes of CRC defined by tumor location (proximal or distal colon, or rectum). When analyzed by source of meat, PhIP from red but not from white meat was nonsignificantly positively associated with CRC and significantly positively associated with proximal cancers [HR (95% CI) per standard deviation increase of log-transformed intake: PhIP red meat: CRC: 1.06 (0.99, 1.12), proximal: 1.11 (1.02, 1.21); PhIP white meat: CRC: 0.99 (0.94, 1.04), proximal: 1.00 (0.93, 1.09)]. Conclusions: Estimated intakes of meat mutagens were not significantly associated with CRC risk over 14 years of follow-up in the NHS and HPFS cohorts. Results for PhIP from red but not from white meat warrant further investigation. Citation: Le NT, Michels FA, Song M, Zhang X, Bernstein AM, Giovannucci EL, Fuchs CS, Ogino S, Chan AT, Sinha R, Willett WC, Wu K. 2016. A prospective analysis of meat mutagens and colorectal cancer in the Nurses’ Health Study and Health Professionals Follow-up Study. Environ Health Perspect 124:1529–1536; http://dx.doi.org/10.1289/EHP238

Although the association between red meat consumption and colorectal cancer (CRC) is well established, the association across subsites of the colon and rectum remains uncertain, as does time of consumption in relation to cancer development. As these relationships are key for understanding the pathogenesis of CRC, they were examined in two large cohorts with repeated dietary measures over time, the Nurses’ Health Study (n = 87,108 women, 1980–2010) and Health Professionals Follow-up Study (n = 47,389 men, 1986–2010). Cox proportional hazards regression models generated hazard ratios (HRs) and 95% confidence intervals (CIs), which were pooled by random-effects meta-analysis. In combined cohorts, there were 2,731 CRC cases (1,151 proximal colon, 816 distal colon, and 589 rectum). In pooled analyses, processed red meat was positively associated with CRC risk (per 1 serving/day increase: HR = 1.15, 95% CI: 1.01–1.32; P for trend 0.03) and particularly with distal colon cancer (per 1 serving/day increase; HR = 1.36; 95% CI: 1.09–1.69; P for trend 0.006). Recent consumption of processed meat (within the past 4 years) was not associated with distal cancer. Unprocessed red meat was inversely associated with risk of distal colon cancer and a weak non-significant positive association between unprocessed red meat and proximal cancer was observed (per 1 serving/day increase: distal HR = 0.75; 95% CI: 0.68–0.82; P for trend <0.001; proximal HR = 1.14, 95% CI: 0.92–1.40; P for trend 0.22). Thus, in these two large cohorts of US health professionals, processed meat intake was positively associated with risk of CRC, particularly distal cancer, with little evidence that higher intake of unprocessed red meat substantially increased risk of CRC. Future studies, particularly those with sufficient sample size to assess associations by subsites across the colon are needed to confirm these findings and elucidate potentially distinct mechanisms underlying the relationship between processed meat and subtypes of unprocessed red meat with CRC.