Cancer Fighting Effects of Olive Oil

• Nutrients
• Evidence of Benefit
• Buying and Storing Olive Oil
• Precautions

Many people use olive oil because of its great taste. Scientific studies have also shown that it has several health benefits. The oil is prepared by crushing and pressing olives. Olive trees (Olea europaea) are believed to be native to Mediterranean countries such as Spain, Syria, and Greece, but evidence suggests they also have their origin in Africa and parts of Asia. Wherever their origin, olive trees have been used as food, medicine, timber, and fuel since time immemorial, with the oil specifically used since 3000 B.C. ^(i.1, 225)

People in the Mediterranean basin use olive oil as a staple in their diets, and many epidemiological and clinical studies have shown low incidences of degenerative brain disease, heart disease, digestive tract cancers, and improved cognitive functioning among this population. Studies also show that people in Europe (e.g., Belgium, France, and Italy) who follow the Mediterranean diet and/or consume olive oil (as opposed to other dietary fats) also suffer less from cardiovascular disease, cognitive degeneration, and cancer. ^{(i.154, 155, 225-227)}

Nutrient Content in Olive Oil

All types of olive oil are rich in monounsaturated fatty acids (MUFAs), which are among the healthy dietary fats. Oleic acid accounts for 75% of the fat content in olive oil. ^{(i.225, 226)}

The extra virgin type is especially rich in polyphenols, which are powerful antioxidants. The antioxidants help in minimizing harmful cellular inflammation and removing unstable molecules. Among the main polyphenols in olive oil is hydroxytyrosol (HT), which triggers changes that enhance antioxidant defense system in the cells of blood vessels at the genetic level. ^(i.225)

Other polyphenols are tyrosols, flavones, flavonols, lignans, secoiridoids, anthocyanidins, hydroxybenzoic acids, and hydroxycinnamic acids. Olive oil also contains beta-carotene, vitamin E, and the rare squalene, an antioxidant that improves skin health. ^(i.225)

Rigorous analysis of 25 population studies have established that the oil helps to reduce the risks of cancers of the upper digestive tract, respiratory tract, breast, and even lower digestive tract. These studies suggest that taking between one and two tablespoons of olive oil a day may be enough to help lower cancer risk. ^(i.225)

How Does It Work?

Olive oil contains polyphenols, nutrients, and unsaturated fatty acids with properties that make them ideal for cancer prevention: ^{(i.225, 227, 228)}

• Anti-inflammatory. Numerous natural compounds in olive oil, such as oleocanthal, oleuropin, hydroxytyrosol, tyrosol, and caffeic acid exert potent anti-inflammatory effects, including inhibiting expression of inflammatory transcription factors.
• Antioxidant. Olive oil alters cell membrane in a way that boosts the antioxidant defense system. Both animal studies and randomized clinical trials in humans show that it also protects DNA from oxidative damage.
• Immune-boosting. Laboratory research indicates olive oil polyphenols help boost natural killing cell activity and help protect against toxins.
• Improves metabolic function. Research indicates olive oil may help decrease insulin resistance, improve fat metabolism, lower cholesterol levels, reduce hypertension, and prevent accumulation of central body fat — all of which are associated with increased risk of cancer or conditions that can lead to cancer, such as non-alcoholic fatty liver disease (NAFLD). In fact, analysis of studies involving diabetics showed that those who consumed diets high in the monounsaturated fatty acids in olive oil (22-33%) had lower cholesterol and blood sugar levels as well as reduced blood pressure.

Evidence of Olive Oil’s Anticancer Effects

Studies showing the beneficial effects of olive oil in specific cancers include: ^(i.228-230)

Buying and Storing Olive Oil

The degree of processing results in different grades. The type with the strongest health benefits is extra virgin olive oil that comes from the initial pressing. Its flavor is also the most delicate, and the oil less acidic, than even virgin olive oil (which can contain up to 2% of free oleic acid). Fresh unrefined olive oil (either virgin or extra virgin) has more antioxidants and unique olive nutrients than pure refined olive oil. ^(i.225)

Other tips for choosing the most healthful olive oil include: ^(i.225)

• Look for traditional cold-pressed olive oil. This method used to extract the oil involves minimal heat without any chemicals. Check the packaging date to ensure freshness — olive oil quickly loses antioxidant power and nutritional quality.
• Choose the ones in dark-tinted bottles because light leads to oxidation and ensure you pick those displayed in cooler areas since heat degrades oil too.
• Check the label for the California Olive Oil Council (COOC) logo which complies with the stricter International Olive Oil Council standards rather than the more lax U.S. ones to ensure you are purchasing extra virgin olive oil.

It is important to store olive oil well in a dark and cool place to maintain freshness and preserve the taste. Tinted glass or ceramic containers are preferable to plastic or metal containers, and only a small amount should be kept out for regular use. Store the rest in the refrigerator and only buy what you can use within two months to ensure the most health benefits and best taste. ^(i.225)

Some suggest that extra virgin oil is not meant for cooking. Heat damages all types of vegetable oil, but extra virgin oil is even more susceptible because it has a low smoke point. Studies show that many, but not all, beneficial cancer-fighting polyphenols and nutrients (e.g., hydroxytyrosol and vitamin E) are significantly damaged or destroyed at temperatures of only 320°-350° F. For example, 60% of oleuropein compounds — powerful antioxidant dihydroxyphenols that lab studies show can kill breast cancer cells — are destroyed within 10 minutes at about 177°C. With the typical temperature used for frying on a stove are between 375-525˚ F, it's easy to see why cooking with olive oil may not be the best option for taking advantage of its many health benefits. ^{(i.229, 231, 232)}

However, results of multiple later studies suggest that substantial heat degradation of most vital olive oil nutrients takes a significant amount of cooking time at high temperatures, with 50-70%. At least one study suggests that the high polyphenol content in virgin olive oil may protect against the formation of acrylamide, a compound formed in certain high-starch processed foods — especially fried potato products (e.g., French fries and potato chips). Since acrylamide is a probable carcinogen, frying potatoes in virgin olive oil may be a better choice than other oils, despite loss of antioxidants from the oil. Further, some beneficial polyphenols in olive oil are resistant to heat degradation, such as tannic acid, and using olive oil when cooking tomato-based dishes (such as those typical of Mediterranean and Italian cuisine) actually helps preserve the cancer-fighting antioxidant carotenoids and flavonoids (such as lycopene) in tomato. ^(i.232-234)

Based on the scientific research, consuming olive oil uncooked is the best option for obtaining the most nutritional benefit from the oil itself. Fortunately, there are many dishes that you can drizzle some of the oil onto before serving. However, frying foods — especially potatoes — at low to moderate heats (up to 180°C) for no more than 15 minutes only causes negligible losses in polyphenols and inhibits the level of acrylamide formed. As a precaution, avoid re-using olive oil for frying; studies show that each time the oil is used more antioxidant components are lost. ^(i.233-235)