Olives are fruits of the tree known as Olea europaea. ‘Olea’ is the Latin word for ‘oil,’ reflecting the olives very high fat content, of which 75% is oleic acid, a monounsaturated fat that has been shown to lower blood cholesterol levels. ‘Europaea’ reminds us that olives are native to the Mediterranean region of Europe.
Olives cannot be eaten right off of the tree; they require special processing to reduce their intrinsic bitterness, caused by the glycoside oleuropein, which is concentrated in their skin. These processing methods vary with the olive variety, cultivation region, and the desired taste, texture and color to be created.
Health Benefits of Olive
Olives are concentrated in monounsaturated fats and a good source of vitamin E. Because monounsaturated fats are less easily damaged than polyunsaturated fats, it’s good to have some in our cells’ outer membranes and other cell structures that contain fats, such as the membranes that surround the cell’s DNA and each of its energy-producing mitochondria. The stability of monounsaturated fats translates into a protective effect on the cell that, especially when combined with the antioxidant protection offered by vitamin E, can lower the risk of damage and inflammation. In addition to vitamin E, olives contain a variety of beneficial active phytonutrient compounds including polyphenols and flavonoids, which also appear to have significant anti-inflammatory properties.
Cellular Protection Against Free Radicals
Vitamin E is the body’s primary fat-soluble antioxidant. It goes after and directly neutralizes free radicals in all the fat-rich areas of the body. In combination, stable monounsaturated fats and vitamin E add a significant safety factor to cellular processes like energy production, a process that generates free radicals even when things are running smoothly.
When cellular processes such as mitochondrial energy production are not well protected, the free radicals produced can interact with and damage any nearby molecules?a process called oxidation. When a cell’s mitochondria become damaged, the cell cannot produce enough energy to supply its needs and dies. If a cell’s DNA becomes damaged, the cell may mutate and become cancerous.
Protection From Heart Disease
Free radical damage can lead to numerous ailments. For example, when free radicals cause the oxidation of cholesterol, the oxidized cholesterol damages blood vessels and builds up in arteries, and can eventually lead to heart attack or stroke. So, by preventing the oxidation of cholesterol, the nutrients in olives help to prevent heart disease.
Support Gastrointestinal Health
If free radicals damage the cellular DNA in colon cells, the cells can mutate into cancer cells. By neutralizing free radicals, the nutrients in olives help prevent colon cancer. A higher intake of both vitamin E and the monounsaturated fats in olives is actually associated with lower rates of colon cancer.
Beneficial Anti-Inflammatory Effects
The anti-inflammatory actions of the monounsaturated fats, vitamin E and polyphenols in olives may also help reduce the severity of asthma, osteoarthritis, and rheumatoid arthritis, three conditions where most of the damage is caused by high levels of free radicals. The vitamin E in olives may even help to reduce the frequency and/or intensity of hot flashes in women going through menopause.
While commonly recognized as a high-fat food (about 80-85% of the calories in olives come from fat), olives are not always appreciated for the type of fat they contain. Olives are unusual in their fat quality, because they provide almost three-quarters of their fat as oleic acid, a monounsaturated fatty acid. (In addition they provide a small amount of the essential fatty acid called linoleic acid, and a very small amount of alpha-linolenic acid, an omega-3 fatty acid.) The high monounsaturated fat content of olives has been associated with reduced risk of cardiovascular disease. 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.
In terms of their phytonutrient content, olives are nothing short of astounding. Few high-fat foods offer such a diverse range of antioxidant and anti-inflammatory nutrients—some of which are unique to olives themselves. The list below shows some key phytonutrients in olives, organized by their chemical category:
- Simple Phenols
- Terpenes (including secoiridoids and triterpenes)
- oleanolic acid
- elenoic acid
- Hydroxycinnamic acids
- caffeic acid
- cinnamic acid
- ferulic acid
- coumaric acid
- Hydroxybenzoic acids
- gallic acid
- protocatechuic acid
- vanillic acid
- syringic acid
- Hydroxyphenylacetic acids
- homovanillic acid
- homveratric acid
Given this phytonutrient richness, it’s not surprising that olives have documented health benefits that extend to most of our body systems. Olive benefits have been demonstrated for the cardiovascular system, respiratory system, nervous system, musculoskeletal system, immune system, inflammatory system, and digestive system. We believe that many of these diverse systems benefits are actually related to two underlying health-support aspects of olives, namely, their unusual antioxidant and anti-inflammatory nutrients. In this Health Benefits section, we will focus on those antioxidant and anti-inflammatory properties of olives, as well as some anti-cancer benefits that seem especially important with respect to this food.
The vast majority of olive phytonutrients listed at the beginning of this section function as antioxidants and help us avoid unwanted problems due to oxidative stress. “Oxidative stress” is a situation in which our cells are insufficiently protected from potential oxygen damage, and oxidative stress can often be related to an insufficient supply of antioxidant nutrients. Olives are a good source of the antioxidant vitamin E, and they also contain small amounts of antioxidant minerals like selenium and zinc. However, it’s the phytonutrient content of olives that makes them unique as an antioxidant-rich food.
Perhaps the best-studied antioxidant phytonutrient found in olives is oleuropein. Oleuropein is found exclusively in olives, and it’s been shown to function as an antioxidant nutrient in a variety of ways. Intake of oleuropein has been shown to decrease oxidation of LDL cholesterol; to scavenge nitric oxide (a reactive oxygen-containing molecule); to lower several markers of oxidative stress; and to help protect nerve cells from oxygen-related damage.
One recent study that caught our attention has shown the ability of olives to increase blood levels of glutathione (one of the body’s premier antioxidant nutrients). In a very interesting research twist, study participants were not given fresh olives to eat but rather the pulpy residue from olives that had been previously milled to produce olive oil. Consumption of this olive pulp was associated with significantly increased glutathione levels in the blood of the participants, and improvement in their antioxidant capacity.
Interestingly, there may be common trade-offs made in the levels of different olive antioxidants during the maturation of olives on the tree. For example, the vitamin E content of olives may increase during early ripening when the total phenolic antioxidants in olives are slightly decreasing. Later on in the maturation process, these trends may be reversed.
In addition to their function as antioxidants, many of the phytonutrients found in olives have well-documented anti-inflammatory properties. Extracts from whole olives have been shown to function as anti-histamines at a cellular level. By blocking special histamine receptors (called H1 receptors), unique components in whole olive extracts help to provide us with anti-inflammatory benefits. In addition to their antihistamine properties, whole olive extracts have also been shown to lower risk of unwanted inflammation by lowering levels of leukotriene B4 (LTB4), a very common pro-inflammatory messaging molecule. Oleuropein—one of the unique phytonutrients found in olives—has been shown to decrease the activity of inducible nitric oxide synthase (iNOS). iNOS is an enzyme whose overactivity has been associated with unwanted inflammation. Taken as a group, these research findings point to olives as a uniquely anti-inflammatory food.
The anti-inflammatory benefits of olives have been given special attention in the area of cardiovascular health. In heart patients, olive polyphenols have been determined to lower blood levels of C-reactive protein (CRP). CRP is a widely used blood measurement for assessing the likelihood of unwanted inflammation. Olive polyphenols have also been found to reduce activity in a metabolic pathway called the arachidonic acid pathway, which is central for mobilizing inflammatory processes.
The antioxidant and anti-inflammatory properties of olives make them a natural for protection against cancer because chronic oxidative stress and chronic inflammation can be key factors in the development of cancer. If our cells get overwhelmed by oxidative stress (damage to cell structure and cell function by overly reactive oxygen-containing molecules) and chronic excessive inflammation, our risk of cell cancer is increased. By providing us with rich supplies of antioxidant and anti-inflammatory nutrients, olives can help us avoid this dangerous combination of chronic oxidative stress and chronic inflammation.
Research on whole olives and cancer has often focused on two cancer types: breast cancer and stomach (gastric) cancer. In the case of breast cancer, special attention has been paid to the triterpene phytonutrients in olives, including erythrodiol, uvaol and oleanolic acid. These olive phytonutrients have been shown to help interrupt the life cycle of breast cancer cells. Interruption of cell cycles has also been shown in the case of gastric cancer, but with this second type of cancer, the exact olive phytonutrients involved are less clear.
One of the mechanisms linking olive intake to cancer protection may involve our genes. Antioxidant phytonutrients in olives may have a special ability to protect DNA (deoxyribonucleic acids)—the key chemical component of genetic material in our cells—from oxygen damage. DNA protection from unwanted oxidative stress means better cell function in wide variety of ways and provides cells with decreased risk of cancer development.
From a botanical standpoint, olives belong to a very special group of fruits called drupes. Drupes are fruits that have a pit or stone at their core, and this pit is surrounded by a larger fleshy portion called the pericarp. Other drupes commonly found in diets worldwide include mango, cherry, peach, plum, apricot, nectarine, almond, and pistachio.
There are literally hundreds of varieties of olive trees, but all of them belong in the same scientific category of Olea europea. “Olea” is the Latin word for “oil,” and reflects the high oil content of this food. Olive trees are native to the Mediterranean, as well as different parts of Asia and Africa. Their Mediterranean origins are highlighted in their species name, europea, since countries bordering the north shore of the Mediterranean Sea are typically considered as parts of southern Europe. Olive trees can have remarkable longevity. Most live to an age of several hundred years, and in at least one case, a carbon-dated world record for an olive tree stands at 2,000 years! Although olive trees may produce more olives in lowland terrain, they are comfortable growing in mountainous, rocky conditions and often thrive along the hillsides of Spain, Italy and Greece.
Olives come in many different varieties. In the United States, five varieties account for most commercial production. These varieties are Manzanillo, Sevillano, Mission, Ascolano and Barouni, and all are grown almost exclusively in California. Picholine and Rubra are two additional varieties produced in California in smaller amounts.
Kalamata olives are one olive variety that deserves special mention. Authentic Kalamata olives come from Kalamon olive trees in southern Greece and get their name from Kalamata, their city of origin. European Union (EU) law provides Kalamata olives with Protected Geographical Status and Protected Designation of Origin and does not allow product labeling as “Kalamata” unless the olives have come from this specific area. However, outside of the European Union countries, there are no binding legal standards for labeling of Kalamata olives. In the U.S., many canned and jarred olives are referred to as “Kalamata-style” or “Kalamata-type” olives and these olives are not authentic Kalamata olives grown in the Kalamata area of southern Greece. Genuine Kalamata olives are usually allowed to ripe fully before harvest. Different methods of curing can be used during production of Kalamata olives. Some Greek producers use dry-curing as a method of choice. In dry-curing, olives are covered directly in salt rather than soaked in brine (a concentrated salt liquid). Dry-curing is often used for olives that will be stored for longer periods of time, and Kalamata olives that have been dry-cured can often be identified by their wrinkly skin. Dry-cured Kalamata olives are eventually packaged in olive oil or olive oil/vinegar combinations to which other seasonings are sometimes added. Kalamata olives can also be cured in a salt brine or in water, and in both cases, red wine vinegar and/or red wine are typically used to give the olives their delicious flavors. Most “Kalamata-style” and “Kalamata-type” olives have been cured in this way. Authentic Kalamata olives from southern Greece that have been cured using red wine and/or red wine vinegar are available in many groceries, especially those groceries that stock specialty foods. Genuine Kalamata olives will almost always be labeled as “imported” and may also be labeled as “PDO Kalamata” to reflect their compliance with European Union regulations.
Kalamata are only one among many Mediterranean olive varieties. The list below contains some of the better-known varieties of Mediterranean olives:
- Lecin de Sevilla
- Santa Cateria
- Gordal Sevillana
When freshly picked from the tree, olives often (but not always) have a bitter flavor. This bitterness is related to their phytonutrient content, and especially to their concentration of oleuropein (a secoirodoid terpene). In order to help offset their bitter taste, olives are typically cured. (Curing is also sometimes referred to as “pickling.”) There are three basic types of curing widely used to lower the bitterness in olives. There types are:
Water-curing of olives—just like the name suggests—involves submersion of the olives in water for a period of several weeks or longer. Water-cured olives typically remain slightly bitter because water-curing removes less oleuropein from the olives than other curing methods.
Brine-curing involves the submersion of olives in a concentrated salt solution. Greek style olives in brine and Sicilian style olives in brine are examples of brine-cured olives. Brine-curing can take many months, and olives often undergo fermentation during the brine-curing process. (Fermentation means that the sugars found in olives will often get broken down into lactic or acetic acid, and oleuropein will be freed to migrate into the brine.) Many changes in flavor and phytonutrient composition can take place during the brine-curing process.