Olive oil: the secret ingredient of the Mediterranean Diet?
Studies have shown that the Mediterranean Diet has tremendous benefits to vascular health, but is Olive Oil the secret ingredient?
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What is the Mediterranean Diet?
While there are many varieties of the Mediterranean diet, it is generally comrpises a high consumption of vegetables, legumes, (whole) grains, seafood, fish, fruits, and supplemented with extra-virgin olive oil, nuts and red wine (2),(3).
What makes the Mediterranean diet different?
You might have heard of diet fads such as the 'low-carb' diet and the 'vegan' diet. Unlike some diet fads, the Mediterranean diet is said to be easier to adopt and able to fill one’s appetite well, with participants in Mediterranean diet studies showing relatively good adherence to the diet (2).
Is it just another useless diet fad?
Termed as a 'poor man's diet' in countries around the Mediterranean Sea, the Mediterranean diet is a dietary pattern that has existed for thousands of years, with it only gaining interest and studied more than half a century ago [1].
Origins of the Mediterranean diet
resource from https://www.aerinle.com/mediterranean-diet-meal-plan/
Why practice it?
Studies have shown that the Mediterranean diet brings about several health benefits, including (and not limited to) (3),(4):
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Better insulin control
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Better blood lipid control
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Reduced inflammation
This also improves aspects of vascular health such as
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Reduced cardiovascular disease risk (5)
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Improved endothelial function (2) (follow this link to find out more)
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Improved blood pressure (2)
With so many health benefits, the Mediterranean diet seems to be a great dietary pattern! So, have you wondered if these beneficial effects are contributed by one or a few components in the diet?
The BIG question
Is olive oil the redeeming factor that is going to protect my vascular health?
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Could we make it easier, please?
A mediterranean diet is not so easy to adopt, and some of our lifestyles, (especially those living in Asia) simply cannot accommodate such a lifestyle.
The truth is, extensive research has been focused around the beneficial effects of olive oil (one of the signature foods that define a Mediterranean diet) in vascular aging. Could this be the shortcut? How much of it do I need to consume? What are its interactions with the other aspects of my lifestyle? (lifestyle, sodium intake) Are there any changes to the benefits that I receive from olive oil if I consume other things with it as well? if I include olive oil in my diet without adhering to a Mediterranean diet, does it work?
If these are your questions, you're at the right place!
Refined vs Extra-Virgin Olive Oil
What's in an olive oil?
Extra Virgin Olive Oil (EVOO), produced from cold pressing olives, is the purer form and preserves the beneficial compounds, (polyphenols, as you will find out later) while refined olive oil degrades them through the extraction process. Moreover, EVOO is unlike regular olive oil which is are generally a mixture of refined and virgin olive oil.
Why does it matter?
Polyphenols: The beneficial compounds of EVOO missing (or reduced) in regular olive oil contains numerous benefits for vascular aging and general health. EVOO has Polyphenols (a type of biological compound) such as Hydroxytyrosol & Tyrosol which have been determined in studies to reduce inflammation and oxidative stress, (6) thereby preventing cellular aging and improved endothelial function (2). (Scroll down to see why!) Don't worry if you're unconvinced, we will be expounding on these shortly!
Monounsaturated fatty acids: The less well studied component of olive oil are monounsaturated fatty acids (MUFA) such as oleic acid. The large amounts of MUFA in EVOO reduce levels of Low-Density Lipoproteins (LDL) cholesterol.(6) Coupled with the antioxidant property of polyphenols, this reduction in LDL cholesterol reduces the chances of LDL oxidation, reducing the risks of cardiovascular diseases (2). Nevertheless, given the patchy evidence regarding the benefits of MUFAs, we will be mainly focusing on polyphenols in this blog.
resource from WIX
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Inflammation & oxidative damage
A crash course
At this point, you may ask, why do our arteries grow stiffer? Why do they dilate less and less? This is because of inflammation - our body's immune response to infections. While this alarm system, usually recruits different weapons (e:g white blood cells) to eliminate the infection, it goes haywire as we age and activates even when there is no infection. This is called chronic, sterile inflammation.
One of the things activated are reactive oxygen species to kill the pathogen. (see slideshow to understand how) But in the absence of pathogens, it damages our own organs and tissues (i.e oxidative damage) instead -think "friendly fire" in a war. This includes our blood vessels resulting in a reduction in endothelium dependent dilation and arterial stiffness. (7)
Ribeiro et al., 2010. Figure: inflammation and endothelial dysfunction. Is exercise training an effective therapy targeting endothelial dysfunction and vascular wall inflammation?
(modified)
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All is well
In a normal healthy individual, no inflammation happens and the endothelium releases vasodilator NO to regulate blood pressure and flow.
In a normal healthy individual who is facing any infection, his endothelium releases vasodilator NO to widen the arteries and regulate blood pressure or flow.
But if you're not too familiar with inflammation, here's a crash course for you...
Numerous studies on human cells have identified the way polyphenols rein in inflammation, and as a consequence, the damaging effects it has on our vascular health. (8), (9), (10), (11), (12)
How does this work? In the cells of our blood vessels, polyphenols interfere with the haywire alarm system (known as NF- kappa-B) that triggers inflammation, reducing the resulting inflammatory response of our arteries and hence reversing the damage done. Just think switching off the alarm, or muffling it to reduce the noise.
In conclusion: olive oil components do exert protective benefits on our blood vessel cells, but we have yet to see its effects on humans...
Hover over to the right to see what do the studies tell us and what do they not?
Hover over to the right to know what NF-kappa-B is and how does it affect vascular health
Is there a science behind olive oil an improvements in my vascular health?
NF kappa B and cell signaling
Think about dominoes, one is pushed and it pushes the other. The same happens in a cell signaling pathway, such as in the NF kappa B pathway. One protein activates another, and in a series of protein activations, NK kappa B, the final protein in line, is activated as well. In its activated form, it can then enter the nucleus and signal the cell to produce more inflammatory proteins. The cell line studies show that polyphenols interfere somewhere along the line, so NF kappa B cannot be activated in the end.
How reliable are these studies?
Studies done on cells (i.e cell line studies) are useful in showing why a certain molecules (polyphenols in our case) exert a certain effect.
You are probably aware that not all cells in our body are the same? Well, some of the cells that were studied resemble in their make-up and function (such as protein composition) those of the endothelial cells. So, when we treat them with polyphenol we are closer to observing an effect that we would see in an actual endothelial cell. One of the studies even tried to simulate the blood composition and environment of someone with high blood glucose (diabetes type II patient)
Nevertheless, we cannot jump the gun to say that they have a confirmed effect on humans as there are many things that need to be considered (like physiologically relevant quantity of polyphenols, how other organs break them down and how they interact with other molecules in our body.)
resource from WIX
Next question: many things can happen in the body. How do I know that the micronutrients in olive oil 1) stay in my body and 2) have a specific effect on blood vessels?
What are the strengths of this study?
Apart from the fact that there are numerous studies which show a similar effect of olive oil polyphenols on vascular health, these studies are done on a human system, taking into account everything in our body.
However, we're not out of the woods. This studies were all done in the context of a Mediterranean diet, which is good news if you are already on one, but it's really iffy if you're not on one and not planning to get on one. Next, the individuals in this study all possessed CVD risk factors, so it may be applicable to you if you are one of those and are trying to slow vascular aging, but we can't assume it has the same effect if you're young and have yet to develop such risk factors, you can't be too sure it has a beneficial effect on you.
resource from WIX
How can I trust the studies?
(Hover over to the left)
Perhaps you are convinced ... maybe not quite. You know that many things can happen to substances in our body. It can leave our circulation and enter the fatty deposits or it can be broken down else where. So how do you know that it still has an effect on our blood vessels?
Some recent studies have shown that individuals displaying risk factors for CVDs displayed a reduction in inflammation in their blood after prolonged (>1 year) adherence to a Mediterranean diet supplemented with olive oil. (13) Another study also showed that this olive oil supplemented diet did lead to improvements in the function of the endothelium. (14, 15)
However, these studies were done on individuals exhibiting the conventional risk factors for CVDs. Scientists still aren't too sure whether the same benefits can be seen in healthy individuals without any signs of vascular aging.
Conclusion: Supplementation of olive oil, when taken together with a Mediterranean diet, could lead to an improvement vascular aging.
How can I trust the studies?
(Hover over to the left)
Several studies done show that the consumption of olive oil out of the context of a proper Mediterranean diet induces mixed effects in individuals: a few studies have shown that it impairs vasodilation (16, 17) rather than improves it. Hence, with the information that we have right now, we would rather err on the side of caution – olive oil while maintaining some semblance of the Mediterranean diet may have some protective function, but we cannot conclude that it would provide the same benefits if we were to consume a vastly different diet composition. There could be many possible reasons, one of which is that different foods in a Mediterranean diet could have substances that work with olive oil to bring about its protective functions.
Something else which suggests that this is a possibility are clinical and cell line studies that show that red wine (another component of the Mediterranean diet) and exert a synergistic effect. (18, 19, 20 ) In other words, when taken together, red wine and EVOO induced an effect which the individual components, when taken separately were not able to induce. This not only includes the levels of hydroxytyrosol in our blood but also the reduction of cytokines inflammatory messengers released by white blood cells during low grade chronic inflammation. (refer to inflammation crash course).
Conclusion: While we are unsure whether olive oil does exert any beneficial effect outside of the context of a Mediterranean diet, conclusive evidence shows that there are synergistic benefits if we consume olive oil together with other components of the Mediterranean diet.
How much can I infer from these studies?
These studies DO NOT confirm that olive oil out of the context of a Mediterranean diet do not have any cardioprotective effect. The scientific method used to conduct the different studies were vastly different and therefore there it would be unreasonable to draw a point-to-point comparison. Moreover, the objective of those studies were not to observe the effect of olive oil on vascular health when other foods of the mediterranean diet were removed. Therefore, the priority of the researchers may not have been to control for variables that may skew the accuracy of the studies.
At the same time, the studies showing synergistic effects suggests, but do not confirm any interactions between the different components of a Mediterranean diet. This is because it was done on cell lines and has yet to be carried out. It shows that there is a likelihood, but we can’t be too certain until other clinical studies have supported this observation.
What if I take olive oil outside of the context of the Mediterranean diet? Is this going to work?
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Is olive oil the be all and end all?
Of course not! We have shown that polyphenols is the part of olive oil that exerts its protective effect, and this molecule can be found in other products as well, such as fruits, vegetables and red wine. (21) In fact, they are found in greater abundance in some other food products. However, if you are thinking about substituting your other oils with EVOO, that may be a wise choice to make nevertheless.
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Where does that leave me?
If you are...
Can't afford a Mediterranean lifestyle
While the protective benefits to cardiovascular aging are still in question when olive oil is taken out of the context of a Mediterranean diet, the general rule of thumb still remains that substitution of olive oil (which is rich mono unsaturated fatty acids and low in saturated fatty acids) do pose some cardioprotective benefits, although they may not be in the context the arterial aging we mentioned
Young and healthy individual
No conclusive studies have been done to prove its benefits, but the identified mechanisms behind the pre-clinical studies suggests that it may be an effective preventive measure to slow vascular aging, while clinical studies show that there is no harmful effect of substituting normal oil with EVOO.
At risk individual for cardiovascular diseases
If you are able to afford (and you do have the discipline to preserve) the elements of Mediterranean diet in your lifestyle, the use of olive oil is likely to provide protective benefits to your blood vessels. It may not reverse all the damage to your blood vessels, but it can slow the aging.
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Done by: Timothy Ng, Cedric Koh, Rayhan Fairuz
References
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3. Davis, C. R., Bryan, J., Hodgson, J. M., Woodman, R., & Murphy, K. J. (2017). A Mediterranean Diet Reduces F2-Isoprostanes and Triglycerides among Older Australian Men and Women after 6 Months. The Journal of nutrition, 147(7), 1348–1355. https://doi.org/10.3945/jn.117.248419
4. Boronat, A., Martínez-Huélamo, M., Cobos, A., & de la Torre, R. (2018). Wine and Olive Oil Phenolic Compounds Interaction in Humans. Diseases (Basel, Switzerland), 6(3), 76. https://doi.org/10.3390/diseases6030076
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12. Catalán, Ú., Hazas, M.-C. L. de las, Rubió, L., Fernández-Castillejo, S., Pedret, A., Torre, R. de la, Motilva, M.-J., & Solà, R. (2015). Protective effect of hydroxytyrosol and its predominant plasmatic human metabolites against endothelial dysfunction in human aortic endothelial cells. Molecular Nutrition & Food Research, 59(12), 2523–2536. https://doi.org/10.1002/mnfr.201500361
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15. Medina‐Remón, A., Casas, R., Tressserra‐Rimbau, A., Ros, E., Martínez‐González, M. A., Fitó, M., Corella, D., Salas‐Salvadó, J., Lamuela‐Raventos, R. M., & Estruch, R. (2017). Polyphenol intake from a Mediterranean diet decreases inflammatory biomarkers related to atherosclerosis: A substudy of the PREDIMED trial. British Journal of Clinical Pharmacology, 83(1), 114–128. https://doi.org/10.1111/bcp.12986
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17. Cortés, B., Núñez, I., Cofán, M., Gilabert, R., Pérez-Heras, A., Casals, E., Deulofeu, R., & Ros, E. (2006). Acute effects of high-fat meals enriched with walnuts or olive oil on postprandial endothelial function. Journal of the American College of Cardiology, 48(8), 1666–1671. https://doi.org/10.1016/j.jacc.2006.06.057
18. Vivancos, M., & Moreno, J. J. (2008). Effect of resveratrol, tyrosol and β-sitosterol on oxidised low-density lipoprotein-stimulated oxidative stress, arachidonic acid release and prostaglandin E2 synthesis by RAW 264.7 macrophages. British Journal of Nutrition, 99(6), 1199–1207. https://doi.org/10.1017/S0007114507876203
19. Karatzi, K., Papamichael, C., Karatzis, E., Papaioannou, T. G., Voidonikola, P. Th., Vamvakou, G. D., Lekakis, J., & Zampelas, A. (2008). Postprandial improvement of endothelial function by red wine and olive oil antioxidants: A synergistic effect of components of the mediterranean diet. Journal of the American College of Nutrition, 27(4), 448–453. https://doi.org/10.1080/07315724.2008.10719724
20. Boronat, A., Martínez-Huélamo, M., Cobos, A., & De la Torre, R. (2018). Wine and olive oil phenolic compounds interaction in humans. Diseases, 6(3), 76. https://doi.org/10.3390/diseases6030076
21. Healthy foods high in polyphenols. (n.d.). WebMD. Retrieved October 11, 2021, from https://www.webmd.com/diet/foods-high-in-polyphenols