Table 4.

Multivariable HR (95% CI) of colon adenomas by site and stage according to quartile of heme iron intake

Proximal colon adenomas (n = 344)Distal colon adenomas (n = 622)
Nonadvanced (n = 240)aAdvanced (n = 104)bNonadvanced (n = 351)aAdvanced (n = 291)b
CasesHRc (95% CI)CasesHRc (95% CI)CasesHRc (95% CI)CasesHRc (95% CI)
Total heme iron (mg/day)
 <0.75471.00281.00661.00641.00
 0.75–<1.07611.39 (0.94–2.05)220.82 (0.46–1.45)911.39 (1.01–1.93)671.09 (0.77–1.55)
 1.07–<1.45741.83 (1.22–2.74)301.14 (0.64–2.03)921.46 (1.03–2.06)891.52 (1.07–2.18)
 ≥1.45581.66 (1.03–2.69)240.98 (0.49–1.95)1021.71 (1.16–2.54)711.36 (0.89–2.10)
Ptrend0.03a0.870.0120.089
Non-nitrosylated heme-iron (mg/day)
 <0.63481.00301.00671.00621.00
 0.63–<0.92601.30 (0.88–1.91)240.76 (0.44–1.32)971.41 (1.03–1.94)651.11 (0.78–1.58)
 0.92–<1.24771.72 (1.15–2.55)260.78 (0.43–1.40)891.29 (0.91–1.83)861.58 (1.10–2.26)
 ≥1.24551.35 (0.84–2.17)240.71 (0.36–1.40)981.46 (0.99–2.15)781.63 (1.07–2.47)
Ptrend0.180.370.120.011
Nitrosylated heme iron (mg/day)
 <0.06521.00231.00741.00761.00
 0.06–<0.13641.30 (0.90–1.89)211.01 (0.56–1.85)861.14 (0.83–1.56)700.91 (0.65–1.26)
 0.13–<0.23631.33 (0.91–1.96)301.59 (0.90–2.82)881.15 (0.83–1.59)740.94 (0.67–1.32)
 ≥0.23611.39 (0.92–2.12)301.86 (1.00–3.46)1031.34 (0.95–1.88)710.92 (0.63–1.33)
Ptrend0.180.0240.100.75
  • aPhomogeneity proximal vs. distal, nonadvanced adenomas = 0.96, 0.96, and 0.99 for total heme iron, non-nitrosylated heme iron, and nitrosylated heme iron, respectively.

  • bPhomogeneity proximal vs. distal, advanced adenomas = 0.46, 0.038, and 0.036 for total heme iron, non-nitrosylated heme iron, and nitrosylated heme iron, respectively.

  • cCox proportional hazards model with the ages of individuals as the time scale, and adjusted on colorectal cancer in first-degree relatives, educational level, smoking status, menopausal status, physical activity, BMI, total energy, intake of alcohol, fibers, dietary and supplemental calcium, and dietary zinc. Nitrosylated and non-nitrosylated heme iron were simultaneously included in the model.