Diet with hyperinsulinaemic potential ups risk of breast cancer

Women with a dietary pattern contributing to hyperinsulinaemia and insulin resistance appear to be at increased risk of breast cancer, particularly estrogen-receptor (ER)-negative and human epidermal growth factor receptor 2 (HER2)-enriched tumours, reveals a study.

A total of 76,686 women from the Nurses’ Health Study (NHS; 1984–2016) and 93,287 women from the NHS II (1991–2017) were prospectively followed in this study. Food frequency questionnaires were used to assess diet every 4 years.

The authors then examined the insulinaemic potential of the diet using the previously established empirical dietary index for hyperinsulinemia (EDIH) based on circulating C-peptide concentrations, wherein higher scores indicated greater insulinaemic potential of the diet. Covariates included reproductive, hormonal, and anthropometric factors (height and body mass index at age 18 years); race; socioeconomic status; total alcohol intake; total caloric intake; and physical activity.

Overall, 10,602 cases of breast cancer (NHS: n=6,689; NHS II: n=3,913) were documented during 4,216,106 person-years of follow-up.

Pooled multivariable-adjusted analyses revealed that women in the highest versus the lowest EDIH quintile (Q) had a high risk of breast cancer (Q5 vs Q1: hazard ratio [HR], 1.15, 95 percent confidence interval [CI], 1.07‒1.24; p_trend<0.01).

The association between EDIH and breast cancer was strongest for ER-negative tumours (Q5 vs Q1: HR, 1.21, 95 percent CI, 1.00‒1.46; p_trend=0.02), although heterogeneity by ER status did not achieve statistical significance. Among tumour molecular subtypes, associations were strongest for HER2-enriched tumours (Q5 vs Q1: HR, 1.62, 95 percent CI, 1.01‒2.61; p_trend=0.02).

“Our findings suggest that dietary modifications to reduce insulinemic potential may reduce the risk of breast cancer,” the authors said.