The timeline of when olive trees were first domesticated remains elusive. However, once this happened, the olive tree quickly became central to the Mediterranean civilizations' trade and economy. Over centuries, it significantly influenced mankind's course and left lasting marks on Western culture.

Fossils indicate that the olive tree originated between 20–40 million years ago during the Oligocene period, primarily in what we now refer to as the eastern Mediterranean. Roughly 100,000 years ago, evidence from the Atlantic coast of Morocco shows that olives were used as both fuel and food.

Around 7,000 years ago, people in Mediterranean areas began cultivating the olive plant, and for the past 5,000 to 6,000 years, olives have been a dietary staple. Further records show olives were consumed in the Levant, and discoveries in Crete highlight their commercial importance dating back to 3000 BC. The Minoan civilization, in particular, found wealth in olives.

Greek history and olives are deeply intertwined. The ancient Greek poet, Homer, referenced olive oil as the "golden liquid," and it's believed its use by humans dates back to 19,000 BC. Greek mythology venerates Athens as the birthplace of the olive tree, with the first tree believed to be planted by the goddess Athena at the Parthenon temple. Subsequently, this tree became sacred to the city. Legend has it that Athena bestowed the olive tree, a fertility symbol, upon the Athenians. In return, they named their city in her honor. The Acropolis in Athens showcased Athena's revered olive tree, while the Academy boasted twelve sacred trees and an esteemed olive grove. This grove's oil became prized rewards at the Panathenaia races. On their coins, Athenians proudly displayed Athena, often featuring an olive wreath or oil amphora. In ancient Greece, the olive symbolized Olympic values like Peace, Wisdom, and Glory. Olympic victors of that era were honored with a wild olive wreath, the "kallistefano." Legend holds that this particular olive tree was brought to Olympia by Heracles after he achieved his renowned twelve labors. Additionally, the iconic statue of Zeus in Olympia, crafted by the legendary Pheidias, was adorned with olive branches.

Early on, the Greeks spearheaded the cultivation of the olive tree in Europe's Mediterranean region. As time went on, Greek settlers and Phoenician merchants introduced the olive tree to other Mediterranean locales. Historian Pliny noted that by 580 BC, regions such as Latium, Spain, and Tunis were still unfamiliar with olive trees and their cultivation.

Olive oil is mainly composed of triacylglycerols and secondarily, by free fatty acids (FFA), glycerol, phospholipids, pigments, flavor compounds and sterols. Triacylglycerols are the major energy reserve for plants and animals. Fatty acid composition of olive oil may vary depending on several factors, such as the variety, maturity of the fruit, altitude, climate etc 5,6.

Fatty acids present in olive oil triacylglycerols are:

• Oleic Acid, a monounsaturated omega-9 fatty acid. It makes up 55 to 83% of olive oil.
• Linoleic Acid, a polyunsaturated omega-6 fatty acid that makes up about 3.5 to 21% of olive oil.
• Palmitic Acid, a saturated fatty acid that makes up 7.5 to 20% of olive oil.
• Stearic Acid, a saturated fatty acid that makes up 0.5 to 5% of olive oil.
• Linolenic Acid, (specifically alpha-Linolenic Acid), a polyunsaturated omega-3 fatty acid that makes up 0 to 1.5% of olive oil 6,7.

Fat soluble vitamins, E and K, can be found in olive oil. The aforementioned vitamins are heat resistant; thus, they are not impaired by cooking. Consequently, they can be stored in the human body for prolonged periods of time, rendering their daily intake not mandatory.

Vitamin E (a natural antioxidant): Olives contain 1.6mg, or 2.3 IU (International Units) per tablespoon. One tablespoon provides 8% of RDA for vitamin E. 

Vitamin K: The richest sources of vitamin K are green, leafy vegetables. For example, one serving of spinach or collards, or two servings of broccoli provide four to five times the RDA. Studies have highlighted the fact that, the greener the vegetable, the higher the content, due to the association of vitamin K with the chlorophyll. According to the USDA, vegetable oils such as olive oil are the second-best source of vitamin K.

 

Olive trees tend to have an inconsistent fruiting pattern. However, with regular fertilization and watering, they produce abundant fruit biennially. As olives mature, their color transitions from green to violet and eventually darkens to brown or black. Olives are categorized based on fruit size into three main types: small olives (primarily for oil extraction), medium-sized or Mesocarps (suitable for both oil and direct consumption), and large olives (exclusively for eating). Here are the detailed types within each category:

Olive oil is the traditional symbol of the Mediterranean diet, representing the primary source of fat. Phytochemicals present in olive oil exert different biological activity, including antioxidant, antiallergic, anti-inflammatory, antiviral, antiproliferative, and anticarcinogenic effects. The health benefits attributed to the dietary use of olive oil are specifically related to extra virgin olive oil consumption, which is considered a key bioactive food because of its high nutritional quality. 

Olive oil provides mono-unsaturated fatty acids (MUFAs), tocopherols, polyphenols as long as, low saturated fats and linoleic/alphalinolenic acid. These fats, have been proven to have positive effects on the immune system and inflammatory responses 8.  In comparison to other fatty acids, such as linoleic, palmitic or steric acids, extra virgin olive oil exhibits up to twenty more times in the concentration of MUFAs.

In 2011, the European Food Safety Authority (EFSA) published a scientific opinion paper regarding the intake of polyphenols from olive oil and their possible protective role in blood lipids against oxidative stress, maintenance of normal blood HDL-cholesterol concentrations, maintenance of normal blood pressure, anti-inflammatory properties, positive contribution to the upper respiratory tract health, maintenance of a normal function of gastrointestinal tract and defense against external agents. Accordingly, the panel proposed that 5 mg of hydroxytyrosol and its derivatives (e.g., oleuropein complex and tyrosol) in olive oil should be consumed daily in the context of a balanced diet for sufficient avoidance of oxidative damage [9]. Hydroxytyrosol is thought to be the main antioxidant compound in olives, and believed to play a significant role in the numerous health benefits attributed to olive oil.

Furthermore, a plethora of research papers have proposed the positive implication of olive oil consumption in:

 

1. Chemopreventive action against certain cancers. A plethora of epidemiological data and studies have repeatedly suggested a protective role of olive oil compounds in several human malignancies, such as breast, colorectal cancer and other types [10–14].

 

2. Protection against cardiovascular diseases. Except for the paper published by the European Food Safety Authority (EFSA) in 2011, which approved health claims that olive oil  protects by its polyphenols against oxidation of blood lipids and for maintenance of normal blood LDL-cholesterol levels by replacing saturated fats in the diet with oleic acid, the United States Food and Drug Administration has approved the health claim that “scientific evidence suggests that eating about 2 tbsp. (23 g) of olive oil daily may reduce the risk of coronary heart disease due to the monounsaturated fat in olive oil [9]. To achieve this possible benefit, olive oil is to replace a similar amount of saturated fat and not increase the overall number of calories consumed in a day”. Furthermore, several studies have shown the hypotensive effect of olive oil through oleic acid [10,15].

 

3. Obesity and diabetes. Obesity, is an increasingly widening condition affecting millions of people mainly in developed countries. The phenolic compounds that are widely present in olive oil have inhibitory effects on obesity and diabetes [16]. Moreover, several olive leaf components have been shown to be effective against obesity, by suppressing molecular factors involved in adipogenesis [17].

 

4. Neuroprotection. A large body of evidence supports the beneficial effects of the Mediterranean diet in preventing neurodegeneration. As the Mediterranean diet is characterized by a high consumption of extra-virgin olive oil it has been hypothesized that olive oil and in particular its phenols, could be responsible for the beneficial effect of the Mediterranean diet 18. Phenols, which can be found in extra virgin olive oil, exert strong antioxidant properties and are able to counteract oxidative stress in brain tissue. Oleuropein and hydroxytyrosol act as direct free radical scavengers, hydroxytyrosol and oleocanthal are strong cyclooxygenases (COX) inhibitors while oleuropein counteracts low density lipoprotein (LDL) oxidations 19.

 

5. Arthritis. Osteoarthritis is a common degenerative disease of the joints among the elderly. Polyunsaturated fatty acids found in olive oil have been associated with the decrease of systemic inflammation. Furthermore, the oleocanthal found in olive oil inhibits the activity of specific enzymes that cause inflammation. Overall, systematic olive oil intake helps to improve health outcomes, as inflammation is a known factor across a variety of chronic diseases 20–22.

 

6. Fertility. Recent scientific data suggest that extra virgin olive oil may be beneficial for fertility whether couples are trying to conceive naturally or are undergoing assisted reproductive treatments or in vitro fertilisation. Results from animal models suggest that olive oil dietary supplementation could be an interesting alternative to enhance sperm quality particularly in aged individuals [23].

 

7. Depression. The effects of olive oil on depression has been of particular research interest as well. Data from patients with severe depression have suggested the beneficial effects of extra virgin olive oil [24]. Overall, several data suggest that fats coming from olive oil, may enhance the central nervous system, helping nerves function properly and increasing levels of the mood-supporting neurotransmitter serotonin.

 

8. Anti-ageing properties. Vitamin E, which is present in olive oil, aids in minimizing the appearance of wrinkles and fine lines. Additionally, it has antioxidants that help defend against free radicals, which speed up aging. Lab studies show that olive oil has potent anti-inflammatory effects on skin and may act as a shield against UV damage. Additionally, monounsaturated fat, which makes up almost 73% of olive oil, is linked to increasedskin firmness and elasticity [10, 25].

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