WARNING!
This is an older article that may not reflect Dr. Mercola’s current view on this topic. Use our search engine to find Dr. Mercola’s latest position on any health topic.
By Dr. Mercola
Olives are one of those wonders of nature that are easy to take for granted, yet deserve special attention. Technically a fruit, olives belong to the group of "drupes," which are fruits with a pit or stone. Other drupes include peaches, mangos, cherries, nectarines, almonds and pistachios.
There are hundreds of varieties of olives, which grow on trees that are mostly native to the Mediterranean (as well as areas of Asia and Africa). Olive trees are remarkable in their own right, as they tend to live to be several hundred years old. There is at least one record of an olive tree that is 2,000 years old.1
In the U.S., five olive varieties make up the majority of the market share: Manzanillo, Sevillano, Mission, Ascolano and Barouni. These are grown mostly in California.
You may also enjoy Kalamata olives, which refer to those from Kalamon olive trees in Greece (they're named after their city of origin, Kalamata). Bear in mind that olives labeled "Kalamata-style" or "Kalamata-type" are probably not true Kalamata olives.2
It's possible to become quite a connoisseur of olives, as each variety has its own unique flavor profile. Olive bars have even become popular at specialty stores, which allow you to taste different olives and curing methods.
Olives Are Anti-Inflammatory, Disease-Fighting Powerhouses
If you love olives, you're in luck. This is one satisfying snack or meal ingredient you can feel good about eating. Many people have shunned olives because of their high fat content, but this is precisely one reason that makes them so very good for you. And there are others as well.
Heart Healthy Fats
Most of the fat (more than 75 percent) in olives is oleic acid, a monounsaturated fat known for lowering your risk of heart disease.
It's worth noting that macadamia nuts also contain high amounts of this beneficial fat (about 60 percent). As reported by the George Mateljan Foundation:3
"When diets low in monounsaturated fat are altered to increase the monounsaturated fat content (without becoming too high in total fat), research study participants typically experience a decrease in their blood cholesterol, LDL cholesterol, and LDL:HDL ratio.
All of these changes lower our risk of heart disease. Recent research studies have also shown that the monounsaturated fat found in olives (and olive oil) can help to decrease blood pressure.
The oleic acid found in olives — once absorbed up into the body and transported to our cells — can change signaling patterns at a cell membrane level (specifically, altering G-protein associated cascades).
These changes at a cell membrane level result in decreased blood pressure."
Research published in the journal BMC Medicine further concluded, "Olive oil consumption, specifically the extra-virgin variety, is associated with reduced risks of cardiovascular disease and mortality in individuals at high cardiovascular risk."4
Powerful Antioxidants and Anti-Inflammatory Properties
Olives contain antioxidants "in abundance," according to research published in the European Journal of Cancer Prevention.5
This includes phenol (hydroxytyrosol, tyrosol), polyphenols (oleuropein glucoside) and other compounds. The antioxidant properties of olives have been shown to be stronger than those of vitamin E.6
Olives also contain some unique antioxidants, like oleuropein, which is only found in olives. It reduces the oxidation of LDL cholesterol in your body and may lower markers of oxidative stress.
Oleuropein also helps to decrease the activity of inducible nitric oxide synthase (iNOS), which is associated with inflammation.7 Oleocanthal, a phenolic compound found in virgin olive oil, even shows similar anti-inflammatory properties to the drug ibuprofen.8
Anti-Cancer Activity
The antioxidant and anti-inflammatory properties in olives, as well as other anti-cancer compounds, make them useful for cancer prevention.
For instance, compounds in olive have been found to activate the tumor suppressor gene and apoptotic gene, which induces programmed cell death. Research published in the International Journal of Clinical and Experimental Medicine reported:9
"Several studies have shown that the incidence of coronary heart disease and cancers is lowest in the Mediterranean basin as compared to other parts of the world because of the diet … rich in olives and olive products.
… Oleic acid, a monounsaturated fatty acid plays an important role in cancer prevention, while squalene showed anticancer effect …
Olive oil shows a role in the prevention of the development of carcinomas and olive oil may have chemopreventive properties against colon carcinogenesis …
Oleuropein is a powerful antioxidant and anti-angiogenic agent and shows a potent anti-tumor agent and cancer-protective effects."
Anti-Aging Benefits
The antioxidants in olives likely yield anti-aging benefits. Tyrosol, a phenol found in extra virgin olive oil, has been found to increase lifespan and resistance to stress in roundworms, for instance. In lab studies, oleuropein-treated cultures had their lifespan extended by 15 percent.10
Oleuropein, hydroxytyrosol (another antioxidant) and squalene in olives may also help protect your skin against the radiation in UV light; oleuropein in particular has been found to act as a skin protector and has direct antioxidant action on your skin.11
And, according to research published in the journal Rejuvenation Research:12
"The health benefits of the Mediterranean diet can be largely ascribed to the nutraceutical properties of extra-virgin olive oil (EVOO).
Mono-unsaturated fatty acids and various phenolic compounds, such as oleocanthal, oleuropein, hydroxytyrosol, and tyrosol, are the main nutraceutical substances of EVOO.
These substances have been suggested to have the ability to modulate aging-associated processes. In experimental models, it has been shown that EVOO with high concentrations of polyphenols has anti-inflammatory and anti-oxidant properties."
Bone Health
Consumption of olive oil and olives has been shown to prevent the loss of bone mass in animal studies of aging-related osteoporosis. Oleuropein may be responsible for this beneficial effect.
In a study of 127 elderly men, consumption of a Mediterranean diet enriched with virgin olive oil for two years was associated with increased serum osteocalcin (a bone matrix protein) and procollagen I N-terminal propeptide (PINP, another measure of bone health), which suggests olives may have protective effects on bone.13
Phenolic compounds in extra virgin olive oil have also been found to stimulate human osteoblastic cell proliferation.14 Osteoblasts are bone-forming cells, so this study also suggests that olives contain compounds that may benefit bone health.
Even More Benefits
Olives, olive oil and compounds in them have been linked to even more health benefits than what's listed above, including:
Increased insulin sensitivity |
Increased testosterone synthesis |
Liver protective |
Beneficial nutrients for eye health (including vitamin A) |
Antimicrobial and anti-viral properties |
Good source of copper, fiber, iron and vitamin E |
What's the Difference Between Black and Green Olives?
Olives come in a range of colors — bright green, yellow green, dark purple, or black. Their color is mostly a matter of preference and doesn't necessarily indicate anything about their state of ripeness or curing process. Some olives turn from green to black during the ripening process, but others start out black and remain black (or start out green and remain green).15
Because olives are bitter when they're first picked, they typically undergo water-curing, brine-curing or lye-curing to make them more palatable. Some olives may also be dry-cured (i.e. rubbed with coarse salt), which results in a wrinkled skin. Most mass-produced olives are cured with lye, as it's a much faster process. The epitome of this would be black canned olives, which are picked green and unripe, then cured in lye and treated with oxygen to turn them black.
If you want to try olives cured with salt or water, a process that takes months, look for small, artisanal brands or pick and choose from a high-quality olive bar. If purchasing from the latter, make sure the turnover rate is high and avoid any olives with a mushy texture.
Both green and black olives are good for you, but there is research that suggests the oleuropein content decreases as olives ripen. So in some cases, green olives may have more of this beneficial compound (but it's not enough of a reason to shun black olives if you enjoy them).16
Olive Oil Is Commonly Adulterated
It's relatively easy to find high-quality olives (look for those with the pits intact and sold in a jar, not a can), but this isn't necessarily the case for olive oil. Olive oil is a common target of food fraud, in which it is deliberately adulterated at your expense, according to the U.S. Pharmacopeial Convention's (USP) Food Fraud Database.17
Even "extra virgin" olive oil is often diluted with other less expensive oils, including hazelnut, soybean, corn, sunflower, palm, sesame, grape seed and walnut. But these other oils will not be listed on the label, nor will most people be able to discern that their olive oil is not pure.
If you live in an area where olive oil is made, buying from a local producer is the ideal solution. If not, try an independent olive oil shop that can tell you about the growers, or at least seek out a brand name that you trust to produce quality oil from your local supermarket.
If at all possible, taste the oil before you buy it. While this won't necessarily be a guarantee of quality (especially if you're not skilled at picking out all the potentially subtle taste differences), it can help you to pick out the freshest-tasting oil possible (and if you open a bottle at home and find that it tastes rancid or "bad," return it to the store for a refund).
And remember, when you need an oil to cook with, coconut oil, not olive oil, is the ideal choice, because it is the only one that is stable enough to resist heat-induced damage. Olive oil is excellent when used for cold dishes, but cooking with it is virtually guaranteed to damage this highly heat-sensitive oil.