Long-Term Olive Oil Consumption Lowers Risk of Diabetes
While studies conducted in the Mediterranean region show an association between olive oil intake and lowered risk of type 2 diabetes, no such study had been conducted in the US, where olive oil consumption is much lower than in Mediterranean countries, according to an article published in the August 2015 issue of the American Journal of Clinical Nutrition.
For the study, researchers from Harvard Medical School and Brigham and Women’s Hospital in the US and two Spanish universities — Rovira I Virgili University and University of Navarra — tested the hypothesis that higher olive oil consumption leads to a lower risk of developing diabetes in the US.
Investigators followed 59,930 nurses, aged 37 to 65 years from the NHS group and 85,157 nurses, aged 26 to 45 years from the NHS II group, two large cohort Nurses Health Studies (NHS) that spanned a period of 22 years. Food frequency questionnaires, completed by the nurses every four years, assessed dietary food intake of more than 130 foods including olive oil consumption in two categories – olive oil as a salad dressing and that added to food or bread.
At the end of the study, the authors identified 5,738 cases of diabetes in the NHS group and 3914 cases in NHS II group.
Results show that nurses who consumed more than one tablespoon or eight grams of total olive oil had a lower risk of developing type 2 diabetes compared to those whose diet did not include any olive oil at all. Additionally, for every eight-gram increase in olive oil consumption, their risk of developing type 2 diabetes decreased by six percent. In this study, the highest daily olive oil intake was 13.25 grams in the NHS group and 20 grams in the NHS II group.
Further analysis showed that subjects who consumed healthier diets along with higher amounts of olive oil reduced their risk of developing type 2 diabetes compared to their peers who consumed high amounts of olive oil but a less healthy diet.
Interestingly, women who consumed olive oil were more likely to have Mediterranean or Southern European roots. They ate more fish, whole grains, fruits, vegetables, and nut; exercised more and had a lower BMI compared to women who never consumed olive oil.
Furthermore, women of Mediterranean/Southern European lineage who consumed high amounts of olive oil had a 23 percent lower risk of developing type 2 diabetes compared to subjects who consumed high intake of olive oil but did not have Mediterranean/Southern European ancestry. This could be because subjects from Mediterranean families probably consumed olive oil as part of their traditional diet for a longer time than those from non-Mediterranean families.
Another interesting finding of the study was that olive oil added to bread or food showed a stronger association in lowering risk of type 2 diabetes compared to olive oil salad dressing. A possible explanation – olive oil added to food or bread is more likely to be extra virgin olive oil while that present in salad dressings is less often based on extra virgin olive oil.
In an additional aspect of the study, the authors found that hypothetically replacing one tablespoon of margarine with one tablespoon of olive oil lowered risk of type 2 diabetes by five percent, while risk reduced by eight percent when replacing butter and by 15 percent when replacing mayonnaise. These results, although hypothetical, indicate that use of olive oil over other sources of fat may lower risk of developing type 2 diabetes.
While this study provides evidence that higher intakes of olive oil lower risk of type 2 diabetes in US women, additional studies are needed to establish the role of olive oil in lowering risk of diabetes. Diabetes is prevalent in 29 million or 9.3 percent of the US population and can lead to serious health problems such as heart disease, stroke, blindness and kidney failure according to the 2014 National Diabetes Statistics Report. It is also a serious health problem worldwide: diabetes incidence in adults was 8.3 percent in 2013 and is expected to rise to about 10 percent by 2035.
According to the authors, “Our results of a 10 percent lower risk of developing diabetes with higher olive oil intake lend additional support to olive oil’s potential role in diabetes prevention, even in populations outside the Mediterranean.”
The study is published in the American Journal of Clinical Nutrition: https://www.ncbi.nlm.nih.gov/pubmed/26156740