- The study behind the headlines
- Which factors to consider when looking at the study conclusions?
- What do the authorities advise?
Recent news stories reported that eating more than half a tablespoon of olive oil a day reduces the risk of dying from heart disease and cancer. While olive oil is a core part of the Mediterranean diet which has long been recognised as a source of nutrients and substances associated with good health, there are a few things to keep in mind when reading the headlines.
The study behind the headlines
The study behind the news used data from two older studies that started in the 70’s and 80’s and followed the diet, lifestyle and health of more than 90.000 participants (around 60.000 women and 30.000 men) over almost 30 years. Researchers then analysed the data specifically to look at the link between olive oil consumption and deaths.
The intake of fats and oils changed over time among participants, with average olive oil consumption increasing and margarine consumption decreasing.
Researchers found that increased olive oil consumption was linked to a lower risk of death overall and by specific causes. More specifically, they observed that participants that had higher intakes of olive oil (over 7 grams a day or half a tablespoon) had 19% less risk of dying from any cause. They were also 19% less likely to die from cardiovascular disease and 17% less likely to die from cancer.
Consistent risk reductions were also seen for deaths from degenerative brain diseases such as Alzheimer’s disease and respiratory diseases.
The researchers concluded that replacing margarine, butter, mayonnaise and other dairy fat with olive oil could decrease death risk. However, there was no evidence that olive oil was preferable to other vegetable oils.
Which factors to consider when looking at the study conclusions?
- It’s difficult to fully ensure that olive oil consumption was the only dietary and lifestyle factor affecting the study’s result.
For example, researchers found that people who consumed more olive oil also tended to have a healthier overall diet and were more physically active. Therefore, it’s difficult to fully ensure that the influence of other lifestyle factors is completely removed from the analysis and so quantify with certainty the direct independent influence of a single factor such as olive oil.
- Food frequency questionnaires may not give the full picture of how much and what type of olive oil is consumed.
Because food questionnaires depend on people’s memory and subjective assessment of portion sizes, it may be difficult for people to accurately estimate their daily consumption of olive oil or other fats across different types of uses (for example, for baking or frying, added to salads or bread, etc.), which may fluctuate over time. The study also did not account for different types and quality of olive oil (for example, refined olive oil or extra virgin olive oil)which may have greater or lesser health benefits.
- “Over half a tablespoon of olive oil a day” may not be necessary as benefits were also seen for smaller intakes.
Although the study found that a higher olive oil consumption was associated with a lower risk for all-cause, cardiovascular and cancer mortality, it’s hard to be sure of the required intake level. Significant risk reductions were also seen with a daily intake of less than a teaspoon of olive oil.
- The study only considered a specific US population and may not be representative of other populations, ethnicities and cultures.
This was a large study but included only middle-aged US health professionals in the 1970s-80s, mostly female and of 98% white ethnicity. More so, the changes in diets and lifestyle over the years add to the difficulty of understanding if the suggested olive oil intakes would have the same potential health influence today.
What do the authorities advise?
- WHO recommends that less than 30% of our energy intake comes from fats, and that unsaturated fats found in vegetable oils (such as olive, sunflower, canola and soybean oils) are preferable to saturated fats from animal products such as butter, cream, cheese, ghee and lard. 1
- Specific recommendations for the consumption and use of different types of fat and oil varies between EU countries. Some countries quantify amounts or recommend overall categories or specific types of oil. Most say to limit saturated or animal fats and to opt for unsaturated or “high quality” vegetable oils. Some countries such as Spain, Greece, Portugal, Romania, Malta, Cyprus and Croatia specify a preference for olive oil. You can find out more about your national dietary guidelines here. 2
- Dietary fats infographic
- The importance of omega-3 and omega-6 fatty acids
- 8 Facts on fats Q&A
- The functions of fats in the body
- What you should know about extra virgin olive oil
- Guasch-Ferré M et al. (2022). Consumption of Olive Oil and Risk of Total and Cause-Specific Mortality Among U.S. Adults. Journal of American College of Cardiology 79(2), 101–112.
- World Health Organisation (2015 updated). Healthy Diet Factsheet No 394.
- . Accessed on 16 Jan. 2022
Quelle: eufic (Last Updated : 19 January 2022)