What's the most important thing people should know about this study as it relates to their health?
Replacing animal fats – such as butter, cream, and mayonnaise – or solid vegetable fat – such as margarine – with olive oil may have a significant health benefit.
What was this study seeking to determine? Has this been done before?
The authors wanted to examine whether olive oil is associated with a lower overall risk of death, as well as risk of death from specific types of disease. The authors had previously reported that greater olive oil consumption was associated with lower risk of cardiovascular disease in the same study groups.
This is the first large prospective study done in the United States. Other studies done in European and Mediterranean countries have shown health benefits of olive oil as part of a Mediterranean diet.
What were the results?
People who used more than 1/2 tablespoon of olive oil daily in their diet had a 19% lower risk of death from any cause and a 19% lower risk of death from heart disease. They also had a 17% lower risk of death from cancer, a 29% lower risk of death from neurodegenerative disease such as Alzheimer's disease, and a 18% lower risk of death from lung disease.
Olive oil is used in much smaller amounts by people living in the United States. In this study, high olive oil intake was defined as
> 1/2 tablespoon of any type of olive oil daily. The benefit increased with increased olive oil intake.
The study did not show that olive oil was superior to other vegetable oils regarding health benefits.
This study does not show causation, only that there is a relationship between greater olive oil use and lower risk of death. The reason for the health benefit remains to be determined.
Did the study reveal any differences concerning sex, gender, or any other subgroups?
Those who consumed more olive oil were more likely to have Mediterranean or Southern European ancestry, be more physically active, be nonsmokers, and eat more fruits and vegetables. After accounting for these and other lifestyle factors and for underlying disease such as diabetes, the study results were unchanged.
Did the authors express and possible reasons for their findings?
Olive oil is high in monounsaturated fatty acids and polyphenols, which have been shown to have anti-inflammatory and antioxidant properties. It can also improve cholesterol and blood sugar control.
What were the strengths and shortcomings of this study's design and execution? How reliable are self-reported nutrition questionnaires?
The strength of this study is that it was done over 28 years and followed a large population (more than 90,000 people). The food survey had been proven valid and was repeated every four years.
There were several shortcomings. The study lacked diversity; most of the participants were non-Hispanic White health care professionals. The type of olive oil was not studied. For example, extra virgin olive oil is higher in polyphenols and would be expected to have greater health benefits than refined olive oil.
What, if anything, should people and health care professionals do differently in the face of these findings? What are the challenges to addressing this issue?
Health care professionals should recommend that people limit intake of animal fats and solid vegetable fats and replace them with at least 1/2 tablespoon daily of olive oil or other unsaturated vegetable oils.
Lifestyle changes can be challenging. Making a recipe change while baking or cooking may take some trial and error. Using olive oil to roast or sauté foods, dress a salad, or in place of a buttery spread can be an easier substitution.
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The information provided here may help you make more informed choices. However, it is not a substitute for an individualized medical opinion or diagnosis, and everyone should always consult with their personal physicians to make decisions about their condition or treatment.