The type of dietary fat consumed, but not necessary the amount, could play a role in type 2 diabetes (T2D) risk according to the first study to evaluate consumption of olive oil and incident T2D among women living in the United States.

This research, appearing in the American Journal of Clinical Nutrition, reviewed data on 59,930 women aged 37–65 from the Nurses’ Health Study (NHS) and 85,157 women aged 26–45 from the NHS II regarding type of dietary fat consumed and risk of T2D. All women were free of diabetes, cardiovascular disease (CVD), and cancer at baseline and were followed for over 22 years with food-frequency questionnaires, self-reported incidence of type 2 diabetes, and supplementary questionnaires to confirm T2D diagnosis. Olive oil consumption was evaluated as salad dressing olive oil, olive oil added to food or bread, and total olive oil intake.

Women with higher olive oil intake tended to consume more fish, whole grains, fruits and vegetables, nuts, and total energy; they also had a higher Alternate Healthy Eating Index (AHEI) score. Mean intake in the highest category (>8g/day, or >1 tablespoon/day) was 13.25g/day in the NHS and 20g/day in the NHS II. Total olive oil intake was associated with a substantially lower risk of developing T2D for both groups and each additional 8g/day intake was linked to a 6% reduced risk of T2D compared to those in the lowest intake group (never/almost never). This was, however, not statistically significant for salad dressing olive oil.  The authors estimate that substituting 8g/day of olive oil for stick (but not tub/soft) margarine, butter, or mayonnaise could reduce T2D risk by 5%, 8%, and 15%, respectively.

Next steps include additional research on the effects of high amounts of olive oil intake, specific varieties of olive oil, and the risk of cardiometabolic disorders.