Our findings are not consistent with a previous conventional epidemiological analysis which found little evidence of an association of circulating GIP concentrations with breast cancer risk (OR for women at and above vs. below median GIP levels: 1.06, 95% CI:0.63–1.84), though this study was restricted to 109 cancer cases and GIP was measured in non-fasting samples which could result in substantial measurement error.23 Here, GIP is linked to cancer.