Story at a Glance:
•For thousands of years, olive oil was valued as much as a medicine as a food, and modern research has largely confirmed that reputation. Most notably, in large randomized trials, adding extra virgin olive oil to a Mediterranean diet reduced heart attacks, strokes, diabetes, and atrial fibrillation.
•Most of olive oil’s benefits come from a small fraction of compounds (e.g., polyphenols) that refining destroys and that degrade with time, heat, and light. As a result, two bottles labeled extra virgin can differ more than tenfold in the compounds responsible for its benefits.
•One of these, oleocanthal, was discovered because it stings the throat the same way ibuprofen does, and it was then found to block the same enzymes. Likewise, olive oil lowers markers of inflammation, and the Mediterranean diet has the most evidence of any diet for helping rheumatologic and autoimmune patients. Additionally, olive oil applied directly to arthritic knees relieved pain better than an NSAID gel.
•Olive oil has long been one of the most commonly faked foods. However, testing shows the larger problem today is genuine oil that has gone stale or rancid before it ever reaches the shelf.
•Contrary to popular belief, extra virgin olive oil holds up to cooking better than most of the oils promoted in its place.
•In this article, we will explore the science behind olive oil, how to recognize fresh oil, the brands we trust, how we use it in our diet, and the olive leaf extracts we use to treat viral illnesses.
One of the greatest problems in medicine today is that everything has become so rushed there is rarely time for a doctor to truly get to know their patients, and as a result, much of what matters most gets lost. Because of this, when I started this newsletter, I hoped to correspond with everyone who reached out to me, but as this publication has grown, that has no longer been possible.
The best solution I’ve found is these monthly open threads, where anyone can ask whatever is on their mind (e.g., questions that have accumulated over the last month). That lets me make a point of replying, and lets others with the same question see the answer. Each month, I also pair the thread with a topic I’ve long wanted to cover but that doesn’t quite warrant its own article.
This month’s topic is olive oil, a food most of us already have in our kitchens, yet few appreciate.
Olive oil is little more than the juice of a fruit, yet few foods have been prized, traded, or counterfeited for as long. For most of human history, “oil” meant olive oil (our word petroleum comes from the Latin for “olive oil from a stone”), and the ancient world ran on it much the way ours runs on crude: as food, fuel, medicine, soap, perfume, and at times, currency.
A Medicine for Millennia
Across the ancient Mediterranean, olive oil was valued as much for healing as for eating, and that reputation persisted for thousands of years.
• Hippocrates called it “the great healer” and described over 60 medical uses for it, from healing wounds and burns to treating ear infections and settling the stomach.
• Pliny the Elder advised that medicinal oil be pressed from olives that had not yet begun to ripen. Modern chemistry confirms early-harvest oil has the highest polyphenol content.
• Into the 20th century, pharmacies in the US and Europe sold olive oil to be taken by the spoonful for digestive problems and high blood pressure.
• In Puglia, many people still drink a small cup of warmed oil each day as a ritual of health.
After World War II, the American physiologist Ancel Keys (who had developed the Army’s K ration) noticed that Greeks and Italians were comparatively free of heart disease despite eating a moderate to high amount of fat, and suspected the difference lay in the type of fat they ate. This led him to launch the Seven Countries Study, which found heart disease was lowest where fat came primarily from olive oil, and to promote what he termed a “Mediterranean-style regime” with olive oil at its core.
Decades later, this was put to a direct test in a randomized Spanish trial of 7,447 people at high cardiovascular risk, where those assigned a Mediterranean diet supplemented with extra virgin olive oil had roughly 30% fewer heart attacks, strokes, and cardiovascular deaths than those advised to cut their fat intake.
Note: Keys’ broader warnings about fat backfired. They helped spark an American war on all dietary fat, olive oil included, and a wave of low-fat processed foods loaded with sugar and salt. The flawed science behind this, along with the dangers of the statins it ultimately gave rise to, is discussed further in The Great Cholesterol Scam and The Dangers of Statins (which can be read here).
Personally, olive oil has become one of the foundations of how I eat. It started as what I cooked and roasted with, but I gradually noticed that a tray of roasted vegetables tasted much better with it, and that I could eat a meal rich in olive oil and feel completely fine afterwards, whereas snacks made with seed oils (and fried food in particular) frequently left me feeling ill. When I read the ingredients of a packaged product, whether it was made with high quality oil or a cheap seed oil is one of the first things I check, as I’ve found it to be a reliable indicator of how much care went into the rest of it. The same holds for restaurants. The occasional one that cooks with olive oil rather than seed oils makes dishes that taste better and leave me feeling better than the same dishes elsewhere, and it tends to be better across the board (as quality ingredients are prioritized—not unlike how the forms of common micronutrients used often indicate a supplement’s overall quality).
Along the way, I also began tasting different olive oils side by side and was surprised by how much they differed. Some were grassy, some buttery, and others so peppery they made me cough, which made me appreciate that olive oil is far more complex than the generic bottles most of us grew up with would suggest. In time, I found that a great deal of research supports what I noticed, and in many cases explains why.
Most notably, the Mediterranean diet has become one of the most consistently supported diets in nutrition research. It is built around vegetables, fruit, legumes, whole grains, nuts, and fish, with olive oil as the primary fat, wine in moderation, and little red meat, sugar, or processed food. Across 12 studies following over 1.5 million people, those who adhered more closely to it had lower rates of death (9%), cardiovascular death (9%), cancer (6%), and Parkinson’s and Alzheimer’s (13%).
Unlike most dietary advice, it has also held up in randomized trials. For example, in the previously mentioned 7,447-person Spanish trial, those given extra virgin olive oil were not only less likely to suffer a heart attack or stroke, but also 40% less likely to develop diabetes and 38% less likely to develop atrial fibrillation, the most common irregular heart rhythm. Likewise, another Spanish trial, which followed 1,002 patients who already had heart disease for seven years, found the diet prevented more heart attacks, strokes, and other major cardiovascular events than the low-fat diet cardiologists have long recommended. Few other diets have been shown to do this.
Note: I view the Mediterranean diet as one of the better diets (rather than the optimal one)—but unlike many of the other ones with merit, extensive research has been conducted that then showed it works, and in practice, we find certain subsets of patients greatly benefit from it.
However, the benefits from the Mediterranean diet were seen in people eating fresh, genuine olive oil (e.g., participants in the first of those trials were given a liter of extra virgin olive oil each week), whereas much of the olive oil sold in America is stale or not truly extra virgin. As such, I believe many Americans who adopt a Mediterranean diet never receive its full benefit, as the oil at its center is often missing the very compounds believed to be responsible for much of it.
Many of the chronic diseases that fill our offices today, such as cardiovascular disease and the degenerative diseases of aging, are driven in part by oxidative stress and inflammation, and extra virgin olive oil supplies compounds that counter both (one of which works much like ibuprofen), within a fat far more stable than the seed oils most people now cook with. Additionally, it requires no pill, prescription, or laboratory to produce, only fresh olives and a mill. Unfortunately, much of what is sold as extra virgin olive oil today has been cut with cheaper oils, made from inferior olives, or degraded by heat and age, and hence contains little of those compounds. Fortunately, genuine oil is still being made, frequently by small producers who grow and mill their own olives and make their oil commercially available.
What’s in Olive Oil
Unlike seed oils (e.g., soybean, canola, and sunflower), which are typically extracted with an industrial solvent and then refined, olive oil is made by crushing the olives and pressing or spinning the oil from the paste, without solvents, chemicals, or refining. Roughly 70% of the fat in olive oil is oleic acid, a monounsaturated fat that is much more stable than the polyunsaturated fats that dominate seed oils, which oxidize substantially faster. Oxidation turns oils rancid, and within the body, oxidative damage helps LDL cholesterol build up in the walls of the arteries.
More importantly, the fats circulating in your bloodstream largely reflect the fats you eat, so a diet rich in olive oil shifts them toward this more stable fat, and oleic acid is generally regarded as one of the healthiest fats we can consume. The heart in particular appears to benefit, as given a choice, it burns fat over any other fuel, and in animal and cell studies, injured hearts treated with oleic acid recovered faster and more completely.
Bottles labeled “olive oil,” “pure,” or “light” are mostly refined oil, yet still contain about as much oleic acid as the best extra virgin oil. What they lack is the remaining 2% of the oil, a mix of over a hundred compounds that refining destroys, and which research credits for most of olive oil’s benefits. The most significant of these are the polyphenols, a large family of plant compounds, many of which act as antioxidants.
In extra virgin olive oil, they are the most abundant natural antioxidants, and have been linked to slowing the progression of diseases driven by oxidative stress, such as cardiovascular disease, cancer, and the degenerative diseases of aging.
Olive oil contains several types: simple phenols, lignans, flavonoids, and secoiridoids. The secoiridoids are found only in the olive’s plant family. Their effects are well enough established that in 2012, European regulators actually approved a health claim stating that olive oil polyphenols protect blood fats from oxidative damage. However, the claim can only be made for oils containing at least 5 mg of hydroxytyrosol and its related compounds per 20 grams (roughly 1.5 tablespoons), the amount it specifies be consumed daily. Relatively few oils on the shelf state whether they meet it, but as I will discuss further below, they can be found.
The most notable of these compounds are:
Hydroxytyrosol: one of the oil’s most potent antioxidants, and the compound the European health claim is built on.
Oleocanthal: the source of the sting at the back of the throat, which inhibits the same enzymes as ibuprofen (discussed further below).
Oleacein: oleocanthal’s chemical sibling, which has shown anticancer and metabolic activity in early laboratory and animal studies.
Squalene and vitamin E: antioxidants that protect the oil itself from oxidation, along with the tissues of those who eat it. The oil’s vitamin E comes primarily as α-tocopherol, its most biologically active form, which the cosmetics industry has long used to shield the skin from sun damage, while squalene is a compound the body uses to build sterols and vitamin D. Olive oil itself has been used as a skin and hair treatment for thousands of years.
Note: in a 2022 analysis of four randomized trials involving over 1,600 patients, olive oil applied to the skin reduced the incidence of pressure ulcers (bedsores) by roughly 44% compared to standard treatments.
One of the least appreciated aspects of olive oil is that many of its most valuable compounds do not exist in the olive. The fruit instead contains oleuropein (along with a close relative called ligstroside), a compound so bitter that a fresh olive is inedible until cured, and since it dissolves in water, most of it would be discarded with the water when the oil is separated. However, once the olives are crushed, an enzyme in the fruit’s flesh strips a sugar off of each, converting them into oil-soluble secoiridoids (e.g., oleacein and oleocanthal), some of which only form during milling. In essence, the same bitterness that makes a raw olive inedible is what becomes the oil’s medicine, and much of that medicine is made in the mill.
Even then, less than 1% of the olive’s phenolics end up in the bottle. Because of this, polyphenol content varies enormously, from roughly 50 to 800 mg per kilogram depending on the olive variety, where it was grown, how ripe it was at harvest, and how it was milled, whereas the European health claim requires about 250 mg per kilogram. Afterwards, both filtering and storage gradually reduce these compounds further. The most medicinally potent are typically your early harvest extra virgin olive oils with a strong and pungent taste, indicative of high polyphenol content, but not always the most palatable in the culinary sense.
Note: this means two bottles legally labeled extra virgin can differ more than tenfold in the very compounds the research credits for olive oil’s benefits.
Oleuropein, however, is not limited to the fruit, as the leaves of the olive tree are far richer in it, and they have a long medical history of their own. By the early 1900s, the British Pharmaceutical Codex listed olive leaves as a remedy for fevers, noting that a decoction of them had been used as a substitute for quinine in obstinate cases. Modern research has since found they have far more to offer. In a randomized trial of patients with high blood pressure, 500 mg of olive leaf extract twice a day lowered blood pressure as effectively as captopril (a commonly prescribed blood pressure drug), while also lowering triglycerides, which the drug did not. Likewise, in overweight middle-aged men, 12 weeks of olive leaf polyphenols improved insulin sensitivity by 15% and the responsiveness of the cells that produce insulin by 28% compared to placebo. So while I generally prefer whole foods to isolated extracts (discussed further below), olive leaf extract is one of the few I consider well worth knowing about.
Note: Olive leaf extract has a surprisingly broad preclinical antimicrobial profile (antibacterial, antiviral, antifungal, and some antiparasitic activity in vitro), while human data and clinical experience are strongest for viral infections—particularly topical use in herpes labialis and supportive symptom/inflammatory modulation in viral respiratory illness. Our own experiences (and many reports online) corroborate its value in treating viral infections—all of which is discussed below.
The Natural Anti-Inflammatory
One of olive oil’s most important medicinal properties was discovered by taste, much as early physicians once judged a plant’s medicinal uses by its taste and smell. In 1999, Gary Beauchamp, a researcher who studies the chemistry of taste and smell, sampled freshly pressed oil at a conference in Sicily and immediately recognized the burn it left at the back of his throat. He had just spent months swallowing ibuprofen for a pharmaceutical study, and experienced how ibuprofen produces an unusual sting felt only in the throat. Since a compound’s sensory qualities often reflect what it does in the body, he suspected the two were related.
He was correct. His team traced the sting to a compound they named oleocanthal (oleo for olive, canth for sting, and al for aldehyde), and found that despite looking nothing like ibuprofen, it inhibits the same COX-1 and COX-2 enzymes (which produce the prostaglandins responsible for swelling and pain). Moreover, at equal concentrations in the lab, oleocanthal blocked 41–57% of COX activity, compared to 13–18% for ibuprofen.
Note: in laboratory and animal studies, oleocanthal has since shown activity against arthritis, Alzheimer’s, and several cancers, which is discussed further below.
In people, the evidence is strongest for joint disease. Of the existing diets, the Mediterranean diet has the most research supporting its use for autoimmune disorders (e.g., see this review and this review), and we’ve found it frequently helps rheumatologic patients. For example, in a randomized trial of 51 rheumatoid arthritis patients, those who switched to a Cretan Mediterranean diet that used olive oil as one of its primary fats had less inflammatory activity, better physical function, and more vitality after twelve weeks, whereas those who stayed on their usual diet saw no change. Likewise, among 365 rheumatoid arthritis patients, those who ate the most olive oil had lower disease activity, particularly those with more severe or long-standing disease. Corroborating this, we have repeatedly observed rheumatologic patients improve from a Mediterranean diet—although many patients cannot get the quality foods and oils (e.g., fresh olive oil and omega-3s) the diet requires, in which case its benefits are much smaller.
Note: there is also some evidence that avoiding seed oils or adopting a ketogenic diet can help autoimmunity.
Olive oil also appears to work when applied directly to the joints. In a small double-blind trial of patients with knee osteoarthritis, olive oil rubbed onto the knee relieved pain more effectively than an NSAID gel, and in another trial, olive oil applied with ultrasound worked as well as an NSAID gel for knee pain in athletes, and faster. More broadly, across 15 randomized trials, olive oil lowered C-reactive protein, and in seven, interleukin-6, two of the body’s key markers of inflammation.
That said, the amount consumed in a typical diet is modest, as 50 grams of fresh oil a day provides roughly 10% of the ibuprofen dose used for pain relief. However, I do not believe this is an issue as chronic low doses of ibuprofen and other COX inhibitors like aspirin, in addition to being much safer, have been shown to have anticancer and anti-clotting effects, and many of the diseases we struggle with are driven by a low-grade inflammation that never fully shuts off. Because of this, a small daily dose of a natural anti-inflammatory may be far more useful than an occasional large one, particularly since regular NSAID use carries considerable side effects (e.g., damage to the lining of the gut).
Note: the hidden costs of conventional pain management medications (and the overlooked alternatives to it) are discussed further here.
This also means you can taste whether your oil contains it, as the sting grows stronger as oleocanthal levels rise. Because of this, Mediterranean tasters have long graded prized oils as “one-cough” or “two-cough” (with the latter considered superior), whereas an oil with no sting at all likely contains very little.
Note: people differ in how sensitive they are to oleocanthal, so an oil that barely tingles for one person can make another cough.
Bioavailability and the Food Matrix
Unlike many plant compounds, which the body absorbs poorly, olive oil’s polyphenols are unusually well absorbed, further strengthening the case for making olive oil a daily part of your diet. Most pass through the mouth and stomach unchanged and reach the small intestine, where hydroxytyrosol and its close relative tyrosol are absorbed at a rate of roughly 40–95% (depending on the dose).
Once absorbed, hydroxytyrosol has been found in rats to concentrate in the liver and kidneys (the organs that filter and process toxins, and hence bear a heavy oxidative load) as well as the brain, as it appears able to cross the blood–brain barrier, which most antioxidants cannot. This is significant, as the brain consumes roughly 20% of the body’s oxygen and is rich in easily oxidized fats, making it one of the organs most vulnerable to oxidative damage.
Note: in toxicity studies, hydroxytyrosol showed no adverse effects at doses up to 500 mg per kilogram of body weight per day, far beyond anything obtainable from food.
Another underappreciated advantage is that some of these compounds can work on both sides of the body’s water–fat divide. The antioxidants in fruit juice and wine are essentially only water-soluble, whereas oleacein dissolves in both water and fat, allowing it to act in watery environments such as the blood as well as fatty ones such as the brain, nerves, and fat cells.
Most importantly, the oil itself appears to be the best delivery system for these compounds. When olive oil polyphenols were given in water, in yogurt, or even added to refined olive oil, they were absorbed less effectively than when they occurred naturally in extra virgin oil, and in a trial of an olive leaf extract, the phenols were better absorbed as a liquid than in capsule form. In other words, every attempt to isolate or repackage these compounds made them less available to the body, not more. This is one of the reasons I generally prefer whole foods to isolated extracts, and researchers have likewise cautioned that olive oil’s phenolics work synergistically, so a single compound pulled out of the oil may not behave the same way on its own.
Note: this mirrors the situation with turmeric and the curcumin in it.
Finally, whatever is not absorbed in the small intestine continues to the colon, where it is fermented by gut bacteria into compounds that can benefit the gut directly (e.g., through a prebiotic-like effect) or be absorbed and act elsewhere in the body, and in mice, extra virgin oil improved the gut microbiota compared to other fats and refined olive oil.
These unabsorbed polyphenols also appear to counter one of the dietary drivers of colon cancer (which is now the leading cause of cancer death in American men under 50 and the second in women under 50). The typical American diet delivers a steady stream of oxidized fats (e.g., from fried foods and reheated seed oils) to the gut, and oxidized frying oil accelerates colon tumor formation in mice. Olive oil’s polyphenols, in turn, counteract this at multiple stages. During simulated digestion, they sharply reduced the formation of the toxic aldehydes (e.g., 4-HNE and MDA) that oxidized fats produce. In human intestinal cells, they blocked the oxidative damage and inflammation caused by dietary oxidized fats. In colon cells, they protected DNA from oxidative damage. Consistent with this, in a large Italian and Swiss study, people who fried with olive oil rather than other oils had a lower risk of colon cancer.
Beyond the Heart: Inflammation, the Brain, and Cancer
Since chronic inflammation plays a role in arthritis, cancer, cardiovascular disease, and Alzheimer’s, olive oil’s anti-inflammatory compounds have been studied in each. Much of this research is still in cells and animals, but it is consistent with what is seen in Mediterranean populations, whose rates of chronic inflammatory disease are among the lowest in the world, and increasingly, with human studies as well. For example, when over 92,000 American nurses and health professionals were followed for 28 years, those consuming more than half a tablespoon of olive oil a day had a 29% lower risk of dying from neurodegenerative disease and a 17% lower risk of dying from cancer than those who rarely consumed it. Notably, the study began in 1990, long before most consumers paid attention to polyphenol counts or harvest dates, so most participants were likely buying whatever olive oil their local supermarket carried. As such, while a fresh, high-polyphenol oil is ideal, even an ordinary bottle of olive oil appears to provide meaningful benefits.
Joints: in cartilage and immune cells, oleocanthal suppressed several of the inflammatory signals (e.g., nitric oxide, IL-6, and TNF-α) that drive the cartilage destruction seen in osteoarthritis and rheumatoid arthritis, leading researchers to argue it should be developed as a treatment for joint disease.
Brain: Alzheimer’s is marked by abnormal beta-amyloid proteins in the brain that clump into plaques between neurons, and tau tangles, twisted fibers of protein that build up inside neurons and choke off their internal transport. In the lab, oleocanthal disrupted the formation of tau tangles and protected neurons from the amyloid fragments, while in mice, it increased the brain’s clearance of beta-amyloid. Likewise, populations following a Mediterranean-style diet have shown up to a 40% lower rate of Alzheimer’s, which hydroxytyrosol’s apparent ability to cross the blood–brain barrier may help explain. More recently, in a six-month trial of adults with mild cognitive impairment, those given a high-polyphenol extra virgin oil (The Governor, at roughly 1,200 mg/kg) showed improved blood–brain barrier function and brain connectivity, which those given refined olive oil did not. Sadly, decades of research focused narrowly on clearing amyloid have produced drugs that deliver barely noticeable benefits at enormous cost and frequently cause brain swelling and bleeding, which suggests that, unlike olive oil (which acts on many aspects of the disease at once), targeting amyloid alone is not enough, while far more promising approaches have been sidelined.
Note: how this happened, and the overlooked treatments that deserve far more attention, are discussed further in The Great Alzheimer’s Scam and The Proven Cures They’ve Buried for Billions (which can be read here).
Cancer: a 2015 Rutgers and Hunter College study found that olive oil’s oleocanthal killed pancreatic, breast, and prostate cancer cells in as little as 30 minutes by rupturing their lysosomes (the cell’s digestive compartments), while leaving healthy cells unharmed. This appears to be because cancer cells have larger, more fragile lysosomes than healthy ones. Likewise, in the randomized Spanish trial of 7,447 adults that compared Mediterranean diets to a low-fat one, women given extra virgin olive oil developed breast cancer at roughly a third of the rate of those advised to cut their fat intake. Additionally, oleocanthal inhibits COX-2, an enzyme many tumors overproduce to fuel their growth, which may help explain why Mediterranean populations have lower rates of breast, prostate, lung, and gastrointestinal cancers than Western ones.
The caveat is that olive oil’s greatest benefits depend on the oil being genuine, and since the earliest written records of olive oil, the trade has been plagued by fraud. That problem has not gone away, as when UC Davis tested imported “extra virgin” oils sold in California, 69% failed the standard. That was far from the only study to find this, and as I will show below, independent testing has repeatedly found similar results (in one case, nearly every bottle tested failed), while police continue to uncover large operations passing off cheaper oils as extra virgin.
For this reason, I’ve put quite a bit of work into figuring out how to find olive oil that actually delivers these benefits. In the final part of the article, I will share how to spot degraded oil, the brands we trust, how we use olive oil in cooking and eating, how we use specific olive leaf extracts for viral illnesses, and how good olive oil became the secret to a healthy “potato” chip that tastes better than the real thing.
