In the subgroup MR analysis of the relative intake of protein and HER2-enriched breast cancer, the IVW showed a protective trend in breast cancer incidence (OR = 0.31, 95% CI = 0.11–0.90, p = 3.13 × 10−2), while MR-Egger manifested an inconsistent nonsignificant estimate. Here, ERBB2 is linked to breast cancer.