The growing interest in olive oil should hardly come as a surprise. After all, we do love the idea of improving our health through the food we eat.
When it comes to health, olive oil is interesting for a few reasons. Perhaps the most significant reason is that olive oil is a key component in Mediterranean diets.
But, when it comes to olive oil itself, two areas jump out. One is the proposed connection between olive oil and inflammation and the other is the way that olive oil may help to reduce the risk of heart disease. Both areas suggest that there are significant health benefits of olive oil, even though there is still a lot that we do not know.
A major challenge is figuring out which benefits are actually supported by science, as there have been a lot of variations in the approaches that studies have taken.
One fairly recent research study looked into this topic (Schwingshacki, Christoph & Hoffmann, 2015). Specifically, the authors were interested to see whether there truly is any evidence suggesting that olive oil can improve markers for inflammation as well as markers of endothelial function.
The Study Itself
This study followed an approach known as a meta-analysis. This means that the authors did not do research on participants themselves. Instead, they were interested in the outcomes of other studies and what the research had to say overall.
Conducting a meta-analysis is a fairly common technique and it’s also a pretty important approach.
For most topics (including olive oil and inflammation), there has been a large range of different studies. Those studies vary considerably from one another, such as variation in their sample populations, the specific parameters they considered, the design of their experiment and in the type of olive oil used.
At the same time, the different studies have also varied in their outcomes.
These issues can make it challenging to see what the overall connection between olive oil and inflammation actually is. A meta-analysis helps with this because it allows authors to see whether olive oil did have a statistically significant effect.
To look at the research into olive oil, the authors pooled results from 30 different studies. Collectively, those studies had 3,106 participants.
They were also intervention studies, where there was one control group and at least one group that was given olive oil.
The amount of olive oil given ranged from 1 mg to 50 mg, depending on the specific study.
Across the studies, the authors found that participants in olive oil intervention groups had significantly lower levels of C-reactive protein and interleukin-6 (markers of inflammation). At the same time, participants in those groups had improved levels of flow-mediated dilation (an indicator of endothelial function).
Statistically, those outcomes indicate that olive oil consumption was able to lower markers of inflammation, while improving markers of endothelial function.
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Implications and Limitations of Outcomes
Overall, the evidence the authors found strongly supports the idea that olive oil can decrease levels of inflammation and may also help to improve endothelial function.
That’s a positive outcome but the authors did note that there were considerable limitations in the conclusions that could be drawn. This isn’t a limitation of the study itself. Instead, it’s connected to the individual research studies that the authors were considering.
As I mentioned earlier, there is a lot of variation in studies into olive oil and inflammation. This is true even when you just consider intervention studies, which often have a similar design to one another.
For example, some studies add olive oil into a regular diet, while others may have participants following a specific diet and then have some of them also supplement olive oil. These variations make it difficult to separate out the effects that olive oil actually had.
Realistically, it’s also likely that the impact that olive oil has on health is going to depend on many factors, including the other components of a person’s diet.
The authors also noted that many studies could not reliably provide information about how much olive oil participants were consuming. In particular, the Mediterranean diet contains significant amounts of olive oil on its own and some studies had people supplementing olive oil on top of that.
This issue means that there is no reliable way to know what levels of olive oil consumption are beneficial for health.
One final issue that the authors noted was that there was considerable variation in the olive oil types, including some studies relying on extra virgin olive oil, while others did not. In theory, extra virgin olive oil should offer the most health benefits because of the way that it is made.
However, there is considerable controversy surrounding extra virgin olive oil, as companies frequently manipulate consumers. In fact, out of the extra virgin olive oil sold in the United States, as much as 80% of it may not actually be extra virgin (3). There is also no guarantee that the studies in question managed to use extra virgin olive oil when they thought they did, as there are currently no reliable tests (4).
Overall, the outcomes and limitations of the research suggest that yes, olive oil can help to decrease markers of inflammation and improve markers of endothelial function. However, more consistent research is needed until we truly know the specific impacts that olive oil has and what dose of olive oil people should be consuming.
More than anything, the outcomes of this study highlight the importance of consistency in research. Right now, the large amount of differences between research studies masks many of the potential effects of olive oil. They also make it difficult to see when olive oil is causing observed effects and when other changes are.
The potential of olive oil for health makes this a critical topic for research and I hope that the quality and consistency of research improves so that we can be certain about the effects that olive oil has.
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