Olive oil, rich in monounsaturated fatty acids, is a major component of the Mediterranean diet.

Populations from that region have longer life expectancies and lower risks of heart disease, high blood pressure and stroke, compared with North Americans and Northern Europeans.

Monounsaturated fatty acids (MUFAs) are considered a healthy dietary fat, as opposed to saturated fats and trans fats.

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Olives are a popular and healthful fruit.

Olive oil is a fat obtained from the fruit of the Olea europaea (olive tree), a traditional tree crop of the Mediterranean region. Whole olives are pressed to produce this distinctive oil.

The oil is used in cosmetics, medicine, cooking, and soaps, and was also used as a fuel for traditional lamps. Olive oil originally came from the Mediterranean, but today it is used worldwide.

In the diet, olives can be eaten whole or chopped and added to pizzas and other dishes.

Over the last 50 years, many studies have looked at the health benefits of olive oil.

Olive oil and the cardiovascular system

Olive oil is the main source of dietary fat in the Mediterranean diet. There appears to be a lower death rate from cardiovascular diseases in the Mediterranean area, compared with other parts of the world.

A review of studies carried out in Barcelona, Spain, looked at the biological and clinical effects of olive oil.

Results suggested that people who regularly consume olive oil are less likely to develop cardiovascular diseases, including hypertension (high blood pressure), stroke, and hyperlipidemia (high blood cholesterol and triglyceride levels).

Olive oil intake also appears to help reduce inflammation, endothelial dysfunction (problems with the inner linings of blood vessels), thrombosis, and carbohydrate metabolism.

Frying with olive oil and heart disease risk

People who regularly eat foods fried in olive oil or sunflower oil do not have a higher risk of heart disease or premature death, researchers from Madrid, in Spain, reported in the BMJ.

The scientists surveyed 40,757 adults aged from 26 to 69 years over an 11-year period. They focused on cooking methods and dietary habits. None of the participants had heart disease when the study started.

The researchers concluded:

"In a Mediterranean country where olive and sunflower oils are the most commonly used fats for frying, and where large amounts of fried foods are consumed both at and away from home, no association was observed between fried food consumption and the risk of coronary heart disease or death."

Fried meals were defined as food that had only been prepared by frying it. Participants were also asked whether their fried food was sautéed, battered, or crumbed.

Frying in extra virgin olive oil may enable food to retain more of their nutrients than boiling, according to research published by the University of Granada in 2016. The scientists say that phenols from the olive oil transfer to foods, making them more healthful.

In 2017, another study found that olive oil is more stable and less likely to change the nutritional value of food that is fried in it, compared with sunflower oil.

Olive oil may help prevent stroke

Scientists in France concluded that olive oil may prevent stroke in older people.

The team found that older people who regularly used olive oil for cooking and salad dressing or with bread had a 41-percent lower risk of stroke, compared with those who never consumed it.

The researchers suggested that olive oil might be a cheap and easy way to prevent stroke, a common problem in older people.

Depression risk and olive oil

People whose diets are high in trans fats may have a higher risk of depression, compared with those whose diets are rich in mono- and polyunsaturated fats. Trans fats are widely used in fast foods and mass-produced items, such as pastries.

According to a study carried out at the University of Las Palmas de Gran Canaria in Spain and published in PLoS ONE, olive oil appears to protect slightly against the risk of depression, even after taking into account people's overall diet, physical activity, and lifestyle.

Data on 12,000 volunteers over a period of 6 years showed that, compared with people whose dietary fat was mainly olive oil, those who consumed trans-fats regularly had a 48-percent higher risk of developing depression.

The more trans-fats they ate, the higher the risk.

Olive oil may reduce breast cancer risk

Scientists from Barcelona in Spain found a key mechanism by which virgin olive oil protects the body against breast cancer, in contrast to other vegetable oils.

After decoding signals in the cells of breast tumors that are activated by virgin olive oil, they concluded that the oil reduces the activity of p21Ras, an oncogene. This oncogene prevents DNA damage, encourages tumor cell death, and triggers changes in protein signaling pathways.

The activity of corn oil, meanwhile, an oil rich in n-6 polyunsaturated fatty acids, appears to increase the aggressiveness of tumors.

The team demonstrated a link between virgin olive oil and a higher incidence of benign, or non-cancerous, breast tumors.

Olive oil helps maintain healthy cholesterol levels

A Japanese study published in the Medical Science Monitor showed that LDL-cholesterol concentrations fell in 28 outpatients who took olive oil supplements once a day for 6 weeks.

Low-density lipoprotein (LDL) is often referred to as "bad cholesterol". The "good cholesterol" is high-density lipoprotein (HDL).

The authors concluded, "These results point to an overwhelmingly beneficial influence of olive oil on the lipoprotein spectrum."

Extra virgin olive oil and Alzheimer's disease

Oleocanthal is a type of natural phenolic compound found in extra-virgin olive oil.

In laboratory experiments with mice, researchers noted that oleocanthal helped shuttle the abnormal Alzheimer's disease proteins out of the brain.

The team looked at whether oleocanthal might help prevent beta-amyloid from accumulating. Beta amyloid is believed to be a key factor in Alzheimer's disease (AD).

Findings suggested that oleocanthal boosts the production of two proteins and key enzymes that help removal beta-amyloid from the brain.

Rates of Alzheimer's disease are lower in Mediterranean countries, where consumption of olive oil is higher than anywhere else in the world.

Researchers in Spain have suggested that following a Mediterranean diet supplemented with additional portions of antioxidant-rich extra virgin olive oil or mixed nuts could help protect cognitive functioning in older adults.

Extra virgin olive oil and acute pancreatitis

Extra virgin olive oil is rich in oleic acid and hydroxytyrosol, which affect the development of acute pancreatitis, or sudden inflammation of the pancreas.

In a laboratory experiment at the University of Granada in Spain, researchers found that the components of extra virgin olive oil appear to protect against acute pancreatitis.

Olive oil and the liver

Investigators from Tunisia and Saudi Arabia carried out a study demonstrating that extra virgin olive oil may protect the liver from oxidative stress.

Oxidative stress refers to cell damage associated with the chemical reaction between free radicals and other molecules in the body.

After giving laboratory rats a moderately toxic herbicide, they were then fed on a diet containing olive oil. It appeared to protect them partially from liver damage.

Olive oil may help protect from ulcerative colitis

Ulcerative colitis causes inflammation of the large intestine, or colon. It is a type of inflammatory bowel disease (IBD) that is similar to Crohn's disease.

Scientists at the United Kingdome say that consuming more olive oil could help fend off ulcerative colitis.

They looked at data for over 25,000 people, aged from 40 to 65 years and living in the U.K. None of them had ulcerative colitis at the start of the study.

The findings showed that the participants with the highest intake of oleic acid, a component of olive oil, had a 90-percent lower risk of developing ulcerative colitis compared to those with the lowest intake.

The researchers suggested that consuming two-to-three tablespoons of olive oil each day could have a protective effect.

According to the United States Department of Agriculture (USDA), 100 milliliter (ml), or 3.5 ounces, of one type of olive oil, contains:

  • Energy: 800 kcal
  • Fat: 93.3 g, or which 13.33 g is saturated and 66.6 g is monounsaturated

It contains no carbohydrate or protein.

Olive oil in the United States

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Olive oil is obtained from the fruit of the olive tree.

The USDA's grading of olive oil is based on flavor, odor, absence of defects, and acidity:

  • U.S. Extra Virgin Olive Oil (EVOO): This has an excellent flavor and odor, and a free fatty acid content of 0.8 g or less per 100g (0.8 percent).
  • U.S. Virgin Olive Oil: This has a reasonably good flavor and odor, and a free fatty acid content of 2 g or less per 100g (2 percent).
  • U.S. Virgin Olive Oil Not Fit For Human Consumption Without Further Processing: This is a virgin oil of poor flavor and odor.
  • U.S. Olive Oil: This is an oil mix of both virgin and refined oils.
  • U.S. Refined Olive Oil: This is an oil made from refined oils with some restrictions on the processing.

These grades are voluntary. Producers do not have to label their product.

In many countries, including the U.S., "light" or "extra light" olive oils are processed with heat and chemicals to take out impurities. The color and flavor is lighter, compared to virgin olive oils. Light olive oil is sometimes blended with other oils.