A dietary pattern that is associated with C-peptide and risk of colorectal cancer in women.

PURPOSE: Higher serum C-peptide concentrations have shown to be associated with an increased risk of colorectal cancer (CRC). Therefore, we used diet information to identify food groups that correlated with fasting serum concentrations of C-peptide and assess the association of this dietary pattern and CRC risk.
METHODS: Major food contributors to fasting C-peptide concentrations were identified with stepwise linear regression in a subsample (n = 833) of women from a large cohort. We then summed the consumption frequency of the major food contributors to form a C-peptide dietary pattern for the entire cohort (n = 66,714). Risk for CRC was computed using Cox proportional hazard model with the C-peptide dietary pattern score as the predictor.
RESULTS: In up to 20 years of follow-up, we ascertained 985 cases of CRC and 758 colon cancer. After adjusting for confounders, the C-peptide dietary pattern, characterized by higher meat, fish, and sweetened beverage intake, but lower coffee, high fat dairy, and whole grains intake, showed direct association with CRC risk (RR comparing extreme quintiles = 1.29, 95 % CI = 1.05-1.58, p trend = 0.048). The same comparison was slightly stronger for colon cancer (RR = 1.35, 95 % CI = 1.07-1.70, p trend = 0.009). In stratified analysis, there was no association between the C-peptide dietary pattern and colon cancer among lean and active women. However, for overweight or sedentary women, RR for the same comparison was 1.58 (95 % CI = 1.20-2.07, p trend = 0.002) (p for interaction = 0.007).
CONCLUSION: We derived a dietary pattern that correlated with C-peptide concentrations. This pattern was associated with an increase in colon cancer, especially among women who were overweight or sedentary.