Olive oil is healthy – right?
Image credit: Unsplash
When it comes to healthy fats, nothing captures the imagination quite like olive oil. Olive oil has enjoyed an extended and well-earned moment in the spotlight in the past few decades, since the Mediterranean diet was popularized in the west. The Mediterranean diet describes a traditionally dietary pattern practiced by populations bordering the Mediterranean Sea, and is characterized by high consumption of vegetables, fruits, legumes, nuts, whole grains, and, of course, olive oil. Enthusiasm for olive oil amongst nutrition and health experts further increased after the results of a large study looking at the health benefits of olive oil were released in 2013 (results were corrected in 2018). The study, called PREDIMED (which stands for “Prevencion con Dieta Mediterranea), was a large, randomized study with 7,447 participants that compared three groups: a Mediterranean diet supplemented with extra virgin olive oil (EVOO), a Mediterranean diet supplemented with nuts, and a control group receiving advice on a low-fat diet. After 4.8 years, the study found that both the EVOO and the nuts group had lower rates of heart attack, stroke, blood pressure, lipids, markers of inflammation and oxidative stress, and death compared to the standard group. The article concluded that diets rich in polyunsaturated fats and polyphenols are especially healthful—especially nuts, and especially olive oil.
In reality, olive oil has been fundamental to the health of the Western world for millennia—well before the results of PREDIMED. Olive oil has a sacred role in several religions. Entire civilizations rose and fell hand in hand with olive oil production. In Rome, there’s a mountain – Monte Testaccio – that was built from the remains of discarded jugs (called amphora) leftover from olive imports. Olive oil was distributed freely to the population of Rome as a sort of social security. It’s estimated that Testaccio contains the remnants of over 50 MILLION of these amphorae.
So, what makes olive oil so special, and why does it get so much attention? The most important component emphasized in PREDIMED and other studies is the type of fat in olive oil. It includes high concentrations of monounsaturated fatty acids (MUFAs). MUFAs are fatty acids that contain a single unsaturated bond in their chain. It also contains some saturated fats (which contain no unsaturated bonds), as well as a moderate level of polyunsaturated fatty acids, or PUFAs, which contain multiple unsaturated bonds. PUFAs include the oft-referenced omega-3 and omega-6 fatty acids and are often considered the primary source of healthfulness of olive oil. PUFAs can be very healthy, but they do come with notable risks. They are particularly delicate molecules and are highly prone to breaking down, through a process called oxidation. This is because the unsaturated part of the molecule is more than happy to react with free radicals in the environment. When this happens, unsaturated fatty acids can form lipid peroxides, which can be extremely harmful to health. This reaction can happen at every unsaturated location in the fatty acid—so the more unsaturated bonds, the higher the risk. Once a PUFA is oxidized through reaction with a free radical, the oxidized chain of the fatty acid can start a chain reaction with other PUFAs and can continue ENDLESSLY until the fuel (the PUFAs) runs out. In fact, this process can happen with any unsaturated fat, whether it’s a PUFA or a MUFA. It’s more likely to happen with PUFAs because there are more unsaturated bonds. A PUFA might be likened to a glass window. The glass window can break easily, and when it does, it can explode into thousands of shards of glass, each of which has the potential to cut you. Every cell in our body is surrounded by a cell membrane that is made from fatty acids – a blend MUFAs, PUFAs, and saturated fatty acids. You can imagine that an oxidative chain reaction in a cell full of PUFAs could cause major issues. And if you think about your brain, these fatty acids are especially critical. By weight, the brain is about 60% fat.
This is where antioxidants come into play. Antioxidants are molecules that clean up free radicals, thus keeping fatty acids in your food (and in your body) safe. Antioxidants include a huge category of compounds—things like vitamin E, vitamin C, alpha lipoic acid, and glutathione often come to mind. In foods, we often think about polyphenols, which are compounds that are designed to protect the plant from oxidative injury. Polyphenols give the color to colorful fruits and vegetables (and is why we talk about “eating the rainbow”, because natural color in foods means polyphenol are present). Antioxidants can stop the chain reactions caused by free radicals—they’re kind of like shatterproof glass.
Why does this matter for olive oil? Olive oil is absolutely LOADED with polyphenols—compounds like oleocanthal, oleacein, and hydroyxtyrosol. Oleocanthal is a natural compound found exclusively in olive oil that has antioxidant, anti-cancer, anti-microbial, and neuro-protective effects. It also has some effects that are like ibuprofen—it inhibits COX-1 and COX-2 enzymes, which are key to inflammation. These polyphenols provide stability to the fatty acids in the oil. And the more polyphenols, the better the olive oil. In fact, European Union regulations note that olive oils that contain more than 5 mg of polyphenols per 20 g of oil belong to the category of oils that “protect the blood lipids from oxidative stress” (regulation 432/2012). High polyphenol olive is cardioprotective, neuroprotective, and anti-inflammatory, and antioxidant. This is why it is the foundational element of the Mediterranean Diet.
But not all olive oils are created equally. Based on the above regulation, to advertise olive oil as having health benefits, producers are legally required to demonstrate high level of polyphenol content. There are five tiers of olive oil, and most of these don’t have the health benefits we often associate with olive oil. The first three of these categories are “virgin” categories – which means the oil can only be produced by mechanical means (without any chemical treatment). Extra virgin olive oil (EVOO) is the highest tier. To qualify as extra virgin, an oil must have certain taste features (the technical terms are fruitiness, bitterness, and pungency) and must have minimal indications of oxidation and other breakdown products (this is measured by free fatty acids and is referred to as “acidity”; less acidity is better). The next tier is virgin olive oil. Virgin olive oil has higher acidity and has defects in the key taste features—more oxidation, less polyphenols, less health benefits. After virgin comes lampante, which literally means “lamp oil”. Lampante is technically virgin – it isn’t chemically refined—but it has even higher acidity and more sensory defects. Because of its defects, lampante is not intended for human consumption. It is meant to be used as industrial fuel. Lampante can, however, be refined, which leads to the next category of olive oil: refined olive oil. Refined olive oil is obtained by refining olive oils that has defects (and is otherwise unfit for human consumption). Refining removes flavors and aroma—and in the process, it also removes protective polyphenols that protect the delicate PUFAs in the oil and provide all the health benefits. Refined olive oil is often blended with higher grade oils (virgin or extra virgin) to improve the flavor, but this does little to improve the overall health characteristics of the low-grade oil. The fifth and final category of olive oil is pomace oil. Pomace oil is produced from the residual paste from the first pressing of olives. A tiny percentage of oil is left in this paste, but it can only be extracted through aggressive processing techniques that involves very high heat, processing with toxic solvents (such as hexane), then extensive processing to remove solvents and other toxins that form during extraction. When sold as food, it is typically blended with some amount of virgin olive oil to enhance its flavor.
This is where things get murkier still. Excellent extra virgin olive oil is difficult to make. It requires harvesting the olives when they haven’t quite reached peak ripeness – at this point the polyphenol content is higher, but the amount of olive that is present is lower, so the yield is also lower. The olives should ideally be processed as quickly as possible, because as soon as they are plucked from the trees, the polyphenols start to break down and oxidation starts to ramp up. It’s helpful to think of olive oil as a fresh fruit juice. This sounds odd, but olives are fruits—they fall into the category of drupes, which are stone fruits (other members of the category include peaches, plums, apricots, and avocados). Fruit juice is best when it’s fresh, and the same is true for olive oil. Things that speed of the deterioration of high-quality olive oil are light, heat, and oxygen. Making high quality olive oil is labor intensive and can be expensive. This is hard to do at large scale. It’s not impossible, but it’s hard. And because olive oil is increasingly popular, and increasingly valuable, producers are incentivized to produce more. But guaranteeing quality is hard, and fraud is shockingly widespread. It’s uncomfortably common for olive oil labeled as “extra virgin” to not actually meet these criteria. For example, in one well-known study that sent shock waves through the olive oil industry, the UC Davis Olive Center found that 69% of imported olive oil failed to meet internationally accepted standards for extra virgin olive oil. Olive oil may also be adulterated, either with lower quality olive oil (like lampante) or even seed oils, like canola or sunflower, because lower quality oils are much cheaper. Doing this is illegal, but it’s very hard to regulate, and is probably common today. It’s very relevant, though, because the healthfulness of the oil is directly related to the quality of the oil. A lower quality oil may be neutral from a health standpoint, or it may be harmful if it’s adulterated. In Spain in 1981, hundreds of people died and over 20,000 became ill after ingesting oil that was marketed as olive oil but was actually rapeseed oil that was contaminated with aniline. Survivors continued to have symptoms, including myalgias and lung and blood abnormalities, in a condition that became known as toxic oil syndrome (TOS). Unfortunately, reports of adulterated or fake olive are not a thing of the past; in July 2024, Italian authorities seized 42 tons of fake extra virgin olive oil worth more than $1 million. Europol, the law enforcement agency for the European Union, recently noted that olive oil fraud is commonplace, and in late 2022 and 2023 helped coordinate operation OPSON, which seized over $30 million euros worth of fraudulent oil and led to over 140 arrests. This was the 12th consecutive year the operation occurred! In addition to potential consequences for the consumer, lower quality oil that presents itself as extra virgin drives down costs, making it much harder for high quality producers to make ends meet (and making it much harder for consumers to know what they’re getting).
So how do you know if your extra virgin olive oil is good? First, you can look at the label. Higher quality oils will be labeled as extra virgin, and that will be the only ingredient in the list. Lower quality oils may just be labeled as “olive oil”, or “refined olive oil”, or “virgin olive oil”, or may be described with words like “pure”, “light”, or “clean”. Any olive oil that contains other oils (like sunflower or canola) SHOULD be labeled as such (but won’t always be). Oils may be labeled as “cold-pressed” or “first-press”; these terms are essentially meaningless based on modern production techniques (all virgin oils would meet these criteria by default). Every olive oil should have a “best by” date, which is typically two years from date of bottling. You want an olive oil that is as close to harvest as possible—within a year, and ideally within 6 months or so. Good olive oils also include the harvest date (or at least harvest season). If it doesn’t, you can figure it out based on “best before” date (although a potential loophole here is that oil may be held for extended periods after harvest but before it is bottled, and the “best before” date is determined based on time of bottling). Excellent olive oils may also test and report the polyphenol content from each harvest and make this report available for review. Second, you can sample the oil. While color isn’t a marker of quality (good oils may be vibrant green or golden), higher quality oils do have key flavor features: fruitiness, bitterness, and pungency. It can take some time to hone the palette, and some of the indicators of quality may be acquired tastes (bitterness, for example, doesn’t immediately jive with everyone’s palette). Certainly, though, good olive oil shouldn’t taste rancid or musty. Third, you can know where your olive oil comes from. If you know the producer or the purveyor, you can cut out some of the middlemen (and some of the risk that the oil isn’t what it claims to be). This is probably easier in places that produce olive oil locally (like California), though specialty producers around the country may produce their own oil in other locations and directly import it, then sell it in local stores and farmers markets. In the Philadelphia area, for example, Byrsa is one such producer with exceptional quality and transparency.
For a deep dive into olive oil, the book Extra Virginity, by Tom Mueller, gives a fascinating rundown of all of this (as well as some resources for finding good oil).
In summary, olive oil—specifically, extra virgin olive oil—is an amazing liquid that has been a cornerstone of health and culture for thousands of years and is central to the Mediterranean Diet, which is one of the best studied and healthiest dietary patterns in the world. Many of the health benefits come from the polyphenols in olive oil, which can help reduce inflammation, protect the brain, and protect the heart. The higher the polyphenol content, the better. Not all olive oil is created equally, though. When you’re buying olive oil, make sure it is extra virgin, and pay attention to the “best before” date and the “harvest date” (if available). Once you open it, use it. Unlike wine, olive oil does not get better with age--the fresher, the better. An added bonus is getting to know your supplier—if you know and trust the person you get your oil from, that’s a real win!
What kind of olive oil is in your pantry?
References
1. Monte Testaccio. Atlas Obscura. http://www.atlasobscura.com/places/monte-testaccio
2. Estruch R, Ros E, Salas-Salvadó J, et al. Primary Prevention of Cardiovascular Disease with a Mediterranean Diet Supplemented with Extra-Virgin Olive Oil or Nuts. N Engl J Med. 2018;378(25):e34. doi:10.1056/NEJMoa1800389
3. Davis C, Bryan J, Hodgson J, Murphy K. Definition of the Mediterranean Diet; a Literature Review. Nutrients. 2015;7(11):9139-9153. doi:10.3390/nu7115459
4. Trichopoulou A, Lagiou P. Healthy traditional Mediterranean diet: an expression of culture, history, and lifestyle. Nutr Rev. 1997;55(11 Pt 1):383-389. doi:10.1111/j.1753-4887.1997.tb01578.x
5. Rivero-Pino F. Oleocanthal – Characterization, production, safety, functionality and in vivo evidences. Food Chem. 2023;425:136504. doi:10.1016/j.foodchem.2023.136504
6. Pang KL, Chin KY. The Biological Activities of Oleocanthal from a Molecular Perspective. Nutrients. 2018;10(5):570. doi:10.3390/nu10050570
7. A cheap and simple test to verify olive oil-related health claims. CORDIS | European Commission. https://cordis.europa.eu/article/id/120839-a-cheap-and-simple-test-to-verify-olive-oilrelated-health-claims
8. Delgado C, Guinard JX. Sensory properties of Californian and imported extra virgin olive oils. J Food Sci. 2011;76(3):S170-176. doi:10.1111/j.1750-3841.2011.02040.x
9. Cavallo C, Caracciolo F, Cicia G, Del Giudice T. Extra-virgin olive oil: are consumers provided with the sensory quality they want? A hedonic price model with sensory attributes. J Sci Food Agric. 2018;98(4):1591-1598. doi:10.1002/jsfa.8633
10. Colquhoun DM, Hicks BJ, Reed AW. Phenolic content of olive oil is reduced in extraction and refining. Asia Pac J Clin Nutr. 1996;5(2):105-107.
11. Lucci P, Bertoz V, Pacetti D, Moret S, Conte L. Effect of the Refining Process on Total Hydroxytyrosol, Tyrosol, and Tocopherol Contents of Olive Oil. Foods Basel Switz. 2020;9(3):292. doi:10.3390/foods9030292
12. Frankel E, Mailer R, Shoemaker C, Wang S, Flynn J. Tests Indicate That Imported “Extra Virgin” Olive Oil Often Fails International and USDA Standards.; 2010. https://1.oliveoiltimes.com/library/ucd-2010-report.pdf
13. Nadeau B, CNN. Italian authorities confiscate almost $1 million in fake olive oil. CNN. Published July 11, 2024. https://www.cnn.com/2024/07/11/europe/italy-olive-oil-seizure-scli-intl/index.html
14. Mueller, Tom. Extra Virginity: the sublime and scandalous world of olive oil. New York: W.W. Norton (2012). https://wwnorton.com/books/Extra-Virginity/
15. BYRSA olive oil. https://byrsa.us/