Red meat consumption has been positively associated with
colorectal cancer; however, the biological mechanism underlying this relationship is not understood. Red meat is a major source of
iron, which may play a role in colorectal
carcinogenesis via increased crypt cell proliferation, cytotoxicity, and endogenous N-nitrosation. In a nested case-control study within the Prostate, Lung, Colorectal, and
Ovarian Cancer Screening Trial, we prospectively evaluated multiple
iron exposure parameters, including dietary intake and serum measures of
iron,
ferritin,
transferrin, total
iron binding capacity (TIBC), and unsaturated
iron binding capacity (UIBC) in relation to incident colorectal
adenoma in 356 cases and 396 matched
polyp-free controls. We also investigated variation in eight key genes involved in
iron homeostasis in relation to colorectal
adenoma in an additional series totaling 1,126 cases and 1,173 matched controls. We observed a positive association between red meat intake and colorectal
adenoma [OR comparing extreme quartiles (OR(q4-q1)) = 1.59, 95% CI = 1.02-2.49, P(trend) = 0.03]. Serum TIBC and UIBC were inversely associated with colorectal
adenoma (OR(q4-q1) = 0.57, 95% CI = 0.37-0.88, P(trend) = 0.03; and OR(q4-q1) = 0.62, 95% CI = 0.40-0.95, P(trend) = 0.04, respectively). Colorectal
adenoma was not associated with serum
ferritin,
iron, or
transferrin saturation or with polymorphisms in genes involved in
iron homeostasis. Serum TIBC and UIBC, parameters that have a reciprocal relationship with overall
iron load, were inversely related to colorectal
adenoma, suggesting that individuals with lower
iron status have a reduced risk of developing colorectal
adenoma.