Olive Oil

SEP 2007

Olea europaea L. Family: Oleaceae

Olive oil , sweet oil

Uses

Olive oil is a nutrient widely used as a salad oil and in cooking, and is a common element in the Mediterranean diet. It is promoted as a beneficial source of dietary fat to improve the lipid profile and reduce cardiovascular morbidity. Olive oil has been used as a vehicle for oily suspensions for injections and is used topically as a demulcent and emollient. Historically, it has been used as a laxative. Clinical trials are limited but have examined olive oil for lowering cholesterol, treating rheumatoid arthritis, and lowering systolic blood pressure.

Dosing

Trials investigating the effect of olive oil have typically employed daily doses ranging from 25 to 40 mL and 8 to 70 g without reported adverse effect. Olive oil at dosages of 30 mL has been used as a laxative.

Contraindications

Contraindications have not been identified.

Pregnancy/Lactation

Generally recognized as safe when used in food. Avoid dosages above those found in food because safety and efficacy in this population are unproven.

Interactions

None well documented.

Adverse Reactions

Ingestion of excessive amounts of olive oil has caused temporary mild diarrhea. Allergic reactions from external use have been rare.

Toxicology

No toxicology has been reported with the use of olive oil.

The olive tree is an evergreen, growing to approximately 10 m in height. Native to Mediterranean regions, olive trees also are cultivated in areas of similar climates in the Americas. The small, leathery leaves are gray-green on top with fine, white, scale-like hairs on the undersides. The ellipsoid olive drupe is technically a fruit, measuring 2 to 3 cm in length. ¹

Records of the olive plant date back to the 17th century BC, and appear to be native to Palestine. ^2, , ^3, Ramses II, Egyptian ruler from 1304 and 1237 BC, is said to have used olive oil for every ailment. ⁴

Olive oil is a fixed oil, expressed from ripe olive fruits. It is pale yellow and may have a greenish tint, depending on the ratio of chlorophyll to carotene. ^3, , ^5, , ⁶

Particular to olive oil is oleic acid (a mono-unsaturated fatty acid), forming approximately 80% of the total fatty acid content, and linoleic acid (a polyunsaturated fatty acid), forming 7% to 10% of the total fatty acid content. Because of the pressing of the drupe rather than extraction by solvents, the lipophilic components of the drupe are retained in the oil. ⁷

In addition, tocopherols, beta-carotene, phytosterols, pigments, terpenic acids, flavonoids (luteolin, quercetin, squalene), and phenolic compounds (eg, oleuropein, tyrosol) are all found in the oil. ⁷

Composition of the oil depends on cultivars, maturation, climate, and other factors. Olive oil is offered in several grades of purity, including virgin oil (initial unrefined oil from first fruit pressing) or pure (lower quality from subsequent pressings). Chemically, the difference between extra virgin and virgin oils pertains to the amount of free oleic acid permitted (4% free oleic acid in virgin; 1% in extra virgin). ^3, , ^4, , ^5, , ⁶

Thin-layer chromatography and gas chromatography analyses are employed to detect adulteration of the oil with foreign oils (eg, cottonseed, peanut, sesame). Certain percentage limits are set for the amounts of saturated fatty acid chain lengths and number of sterols. ³

Olive oil is a nutrient, widely used as a salad oil and in cooking, and is a common element in the Mediterranean diet. ^4, , ^8, , ^9, , ¹⁰ The relative safety of olive oil and the availability of randomized clinical trials in humans render data from animal trials largely irrelevant.

Cardiovascular conditions Interest in the potential of olive oil to reduce cardiovascular disease has largely come about through epidemiological studies correlating consumption of Mediterranean diets rich in olive oil with positive health outcomes. ⁷

Studies have sought to establish outcomes related to differing phenolic (and other) content of the oil, ^11, , ^12, , ^13, , ^14, , ^15, and the detrimental effect of heating. ^16, , ¹⁷ Most, but not all, studies have shown a concentration-dependent effect of phenolic content on activity of the oil: higher phenolic content equating greater effect. Fewer clinical studies of sound methodological quality measuring nonsurrogate markers of cardiovascular outcomes exist.

In normotensive and hypertensive elderly patients, consumption of olive oil reduced systolic blood pressure but not necessarily diastolic pressure. ^18, , ^19, , ^20, Olive oil consumption lowered systolic blood pressure in patients with stable coronary heart disease ^21, but not in patients with chronic heart failure. ^22, In patients with metabolic syndrome, consumption of olive oil 8 g/day over a 2-year period reduced insulin resistance, mean body weight, and cardiovascular risk. ²³

In healthy volunteers, mildly dyslipidemic, or diabetic (type 2) patients, olive oil has been compared with butter, sunflower oil, flaxseed oil, rapeseed oil, walnuts, and fish oils in long-term, medium-term, or single-test studies. Results have largely favored olive oil interventions, but data are not always consistent. ^24, , ^25, , ^26, , ²⁷

Mechanisms proposed for olive oil's activity include its influence on the lipid profile, ^12, , ^15, , ^17, , ^28, , ^29, , ^30, thromboxane production, ^24, nitric oxide production, endothelial function, ^11, low-density lipoprotein oxidation, plasma antioxidant capacity, ^12, , ^13, , ^14, , ^15, , ^16, , ^17, , ^24, , ^26, , ^28, activation of nuclear transcription factor in atherosclerotic plaque formation, ^25, and serum insulin/glucose response. ^29, , ^30, , ³¹

Clinical nutrition The use of olive oil as a nutritional source in intensive care patients has been studied. In trauma patients, olive oil was compared with glucose-based nutrition. Olive oil was well tolerated, and a decrease in intensive-care-unit stay occurred despite some methodological limitations to the study. ^32, In preterm infants, olive oil was compared with soybean oil with no adverse reactions in either group, and an improved vitamin E status (and consequently inferred lower oxidative stress) in the olive oil group. ³³

Cancer A nutrition review of dietary fat and chronic disease risk revealed that mono-unsaturated oils such as olive oil are weak promoters of certain cancers (eg, breast, colon) compared with promoters such as n-6 polyunsaturated oils. ³⁴

An epidemiological case-control dataset found olive oil to be protective against laryngeal cancer in women (odds ratio = 0.3 [95% confidence interval = 0.1 to 0.9]) and possibly protective against upper GI tract cancer. ³⁵

Olive oil and cancer prevention have been inversely correlated in experimental models with animals. In rats, olive oil had no colon tumor-enhancing effects compared with other fatty-type diets. ³⁶

Rheumatoid arthritis Olive oil was used as a placebo in many trials studying oils. In a placebo-controlled trial of fish oils in patients with rheumatoid arthritis, improvement in the disease process was noted in both groups (despite methodological limitations of the study). ^37, Decreased tendency to develop spontaneous osteoarthritis was demonstrated in mice fed olive oil compared with other fats. ³⁸

Antibacterial The plaque-inhibitory action of an olive oil dentifrice has been demonstrated. Adhesion and growth of bacteria were inhibited versus a conventional fluoride wash. ³⁹ Other experiments showed olive oil exhibited in vitro antimicrobial properties against gram-negative bacteria, fungi, and enterotoxin B production by Staphylococcus aureus . ^40, , ⁴¹

Other uses Olive oil is classified as a pharmaceutical acid. ^4, It is used as a vehicle for oily suspensions for injection and is a drug solvent. ^5, , ⁴²

The effectiveness of certain attributes of olive oil are not well documented. ^43, Olive oil is a mild laxative and has been used as an intestinal lubricant. ^42, There are claims that it is useful for gall bladder problems, including cholecystitis and cholelithiasis. ⁴³

Externally applied, olive oil acts as a demulcent and emollient. It is used to soften the skin in eczema and psoriasis, and in massage, and used to prevent stretch marks; therefore, it is employed in the preparation of soaps, ointments, and liniments. ^3, , ⁵ In addition, olive oil has been used to soften ear wax.

Trials investigating the effect of olive oil have typically employed daily doses ranging from 25 mL ^12, to 40 mL ^14, and 8 g ^23, to 70 g ^13, without reported adverse reaction. Historically, olive oil at dosages of 30 mL has been used as a laxative. ⁴⁴

Safety and efficacy in this population are unproven. Generally recognized as safe when used in food. Avoid dosages above those found in food.

None well documented.

Ingestion of excessive amounts of olive oil has resulted in temporary mild diarrhea. ^4, In rare cases, topical use of olive oil has caused allergic reactions. ⁴³

No toxicology has been reported with the use of olive oil.

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