Scientific Name(s): Olea europaea L.
Common Name(s): Olive oil, Sweet oil
Olive oil is a nutrient widely used as a salad oil and in cooking. It has also been used as a vehicle for oily suspensions for injections, topically as a demulcent and emollient, and as an enema. Historically, it has been used as a laxative. Olive oil is an element of the Mediterranean diet and is promoted as a beneficial source of dietary fat to improve the lipid profile and reduce cardiovascular morbidity. Clinical trials are limited and generally have been conducted as part of epidemiological studies to validate observed cardiovascular effects and glycemic response.
Trials investigating the effects of olive oil have been as low as 4 mL/day but typically used daily doses ranging from 25 to 40 mL and 8 to 70 g without reported adverse effects. It has been used topically to soften ear wax, incorporated into creams for topical application, and administered as an enema for constipation.
Contraindications have not been identified.
Generally recognized as safe (GRAS) when used as food. Avoid dosages above those found in food because safety and efficacy are unproven.
None well documented.
Ingestion of excessive amounts of olive oil has caused temporary mild diarrhea. Allergic reactions from topical use have been rare.
No toxicology has been reported.
The olive tree is an evergreen, growing to approximately 10 m in height. Native to Mediterranean regions, olive trees also are cultivated in 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 (fruit) measures 2 to 3 cm in length.1
Records of the olive tree date back to the 17th century BC. It appears to be native to historical Palestine. Ramses II, Egyptian ruler from 1304 and 1237 BC, is said to have used olive oil for every ailment.2, 3, 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. Olive oil is composed largely of esters of oleic acid (an n-9 mono-unsaturated fatty acid), forming approximately 80% of the total fatty acid content. Linoleic acid (a polyunsaturated fatty acid) and saturated palmitic acid form the balance of the fatty acid content.
In addition, approximately 200 other chemical compounds have been identified in the oil including tocopherols, beta-carotene, phytosterols, pigments, terpenic acids, flavonoids (luteolin, quercetin, squalene), and phenolic compounds (eg, oleuropein, tyrosol).
Composition of the oil depends on the cultivar, stage of drupe maturity, 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).
Thin-layer chromatography and gas chromatography analyses are used to detect adulteration of the oil with foreign oils (eg, cottonseed, peanut, sesame). Limits are set for the amounts of saturated fatty acid chain lengths and number of sterols.3, 4, 5, 6, 7, 8
Uses and Pharmacology
Olive oil is a nutrient widely used as a salad oil and in cooking, and is a common element in the Mediterranean diet.4, 9, 10 Studies have sought to establish outcomes related to differing phenolic (and other) content of the oil11 and the detrimental effect of heating.12, 13, 14 Most, but not all, studies have shown a concentration-dependent effect of phenolic content on activity of the oil; higher phenolic content is equated with greater benefit.
The plaque-inhibitory action of an olive oil dentifrice has been demonstrated. Adhesion and growth of bacteria were inhibited with olive oil in comparison with conventional fluoride wash.67 In other experiments, olive oil exhibited in vitro antimicrobial properties against gram-negative bacteria, fungi, and enterotoxin B production by Staphylococcus aureus.68, 69 Modest efficacy of olive oil for eradication of Helicobacter pylori was demonstrated in one small study.79
Compared with standard treatment with phenytoin cream, topical application of an aloe vera:olive oil (3:2) cream for 30 days was found to improve wound healing and pain severity significantly better in Iranian adults (N = 60) with pressure ulcers, diabetic wounds, and venous ulcers who were enrolled in a randomized, double-blind, comparator-controlled trial. No adverse events were reported by participants.87 Similarly, no risk differences for pressure ulcers incidence were found between topical application of extra-virgin olive oil (97% olive oil) or standard therapy (hyperoxygenated fatty acids) after 16 weeks in a noninferiority, triple-blind, parallel, multicenter, randomized trial (N = 831).88 A randomized controlled trial in 104 Iranian adults with deep second degree burn wounds covering 10% to 20% total body surface area evaluated the effects of oral olive oil on daily occurrence of wound infection, sepsis, healing of grafted skin, duration of wound healing, and duration of hospital stay compared to control (sunflower oil). The olive oil dose was given as 20% of the total daily energy requirement. A statistically significant reduction in mean duration of wound healing was found in those receiving olive oil versus control (7.2 vs 8.7 days, respectively; P = 0.04) with a mean reduction in duration of hospitalization of 7.4 versus 8.9 days, respectively (P = 0.05).89
The relative safety of olive oil and the availability of randomized clinical trials in humans render data from animal trials mostly irrelevant.
Interest in the potential of olive oil to reduce cardiovascular disease has derived from epidemiological studies correlating consumption of Mediterranean diets rich in olive oil with positive health outcomes, as well as the PREDIMED 5-year Mediterranean diet intervention study.6, 15 Few clinical studies exist with sound methodology using nonsurrogate markers of cardiovascular outcomes; additionally, olive oil has been used as placebo in trials of omega-3 supplementation after coronary surgery.16, 17 In 2014, a review found 9 case-control and cohort studies for inclusion in a meta-analysis to estimate the effects of olive oil consumption on risk of stroke and risk of cardiovascular disease (CVD). Participants had no history of CVD at baseline. All 3 studies (n = 38,673) with data on stroke consistently reported a significant inverse relationship between olive oil consumption (25 g/day) and risk of stroke (combined relative risk [RR], 0.76; P < 0.001) with no substantial heterogeneity; this included data from the PREDIMED study. No significant association was found for risk of coronary heart disease (n = 101,460). When data for coronary heart disease and stroke was used, the combined RR of CVD was 0.82 (P = 0.01); however, significant heterogeneity was observed.83 An observational prospective cohort study conducted from within the PREDIMED study assigned 7,447 participants at high cardiovascular risk to a Mediterranean diet (MedDiet) supplemented with extra-virgin olive oil (EVOO), MedDiet with nuts, or advice on a low-fat reference diet. Participants were followed for a median of 4.8 years to evaluate the benefit of olive oil consumption on the risk of cardiovascular disease and mortality. Baseline EVOO was inversely associated with major cardiovascular events (P for trend < 0.01); for each 10 g/day increase in EVOO consumption, cardiovascular disease and mortality risk decreased 10% and 7%, respectively. Additionally, risk reduction in major cardiovascular events according to tertiles of baseline olive oil consumption was 57% for MedDiet with EVOO and 55% for MedDiet with nuts (P for trend < 0.01 for each) compared with a 9% increase in risk in the control group.84 Another trial comparing an olive oil-rich Mediterranean diet against a low-fat diet is underway in coronary patients to evaluate dietary pattern on secondary prevention of coronary heart disease.90
Mechanisms proposed for olive oil's activity include its influence on the lipid profile13, 18, 19, 20, 21, 22; markers of endothelial function, inflammation, and coagulation;10, 11, 23 nitric oxide production; low-density lipoprotein (LDL) oxidation; plasma antioxidant capacity12, 13, 18, 19, 20, 24, 25, 26; and serum insulin/glucose response.21, 22, 27
In normotensive and hypertensive elderly patients, consumption of olive oil reduced systolic blood pressure but not necessarily diastolic pressure.28, 29, 30 Olive oil consumption lowered systolic blood pressure in patients with stable coronary heart disease31 but not in patients with chronic heart failure.32 A small (n = 24), randomized, single-blind, crossover study in women with stage 1 hypertension found significant reductions in systolic blood pressure and diastolic blood pressure with polyphenol-rich olive oil compared with polyphenol-free olive oil.78 Similar results were found by a meta-analysis of high (ie, virgin or extra virgin) versus low (refined) polyphenol olive oil supplementation; 8 randomized clinical trials (N = 355) were included in the analysis with daily intake of phenols ranging from 0 to 31 mg for durations ranging from 3 weeks to 3 months (median, 3 weeks). Statistically significant beneficial effects were seen for high polyphenol olive oil on systolic blood pressure (P < 0.01) and oxidized LDL (P = 0.05) but not on other cholesterol parameters or malondialdehyde.85
Markers of atherosclerosis have been studied in healthy volunteers, in hyperlipidemic and stable coronary heart disease patients, and in elderly patients, including subpopulations of the European Prospective Investigation into Cancer and Nutrition study (EUROLIVE) and Three-City study.33, 34, 35, 36, 37, 38, 39 In most analyses, decreased inflammatory status was associated with the intake of phenolic-rich olive oil; however, some studies found only marginal benefits.34, 35, 40, 41, 77
Studies in healthy volunteers and in hyperlipidemic adults and children have generally shown improved lipid profile with consumption of virgin olive oil.19, 22, 41, 42, 43, 44, 45 Increases in phenolic and oleic acid content of the LDL were measured in EUROLIVE study participants and probably contributed to decreased LDL-oxidation.26, 43, 46, 47
In the PREDIMED clinical trial, high adherence to the Mediterranean diet was associated with decreases in the occurrence of metabolic syndrome and type 2 diabetes.15, 48, 49 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.50 Assessment of data from 6,705 participants without baseline atrial fibrillation in the PREDIMED trial also revealed a significant relevant reduction in risk of atrial fibrillation (38%) with the Mediterranean diet supplemented with extravirgin olive oil (EVOO; ≥ 50 g/day). Higher consumption of EVOO (≥ 15% of total energy intake) yielded the strongest reductions in atrial fibrillation incidence.82
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.51 Olive oil may influence carcinogenic processes via signaling pathways, reduced oxidative stress (due to antioxidant oleic acid, vitamin E, and polyphenol content), and reduced DNA damage. Oleic acid may also regulate receptors, such as human epidermal growth factor 2.23, 52
Despite concerns that monounsaturated oils, such as olive oil, are weak promoters of certain cancers (eg, breast, colon) compared with n-6 polyunsaturated oils53 reviews of epidemiological case-control datasets have found olive oil to be potentially protective against upper GI tract cancers (oral cavity, pharynx, esophagus, and larynx) but equivocal regarding colorectal cancers.52, 54 For high levels of olive oil consumption, a meta-analysis of the available data for breast and gynecological cancers is supportive of a risk reduction of 0.62 (95% confidence interval, 0.44 to 0.88).52 Heterocyclic amines released during cooking have been shown to be mutagenic in bacterial and animal studies. A large, multicenter, case-control study evaluated the potential effect of fried foods on colorectal cancers (1,394 colon cancer, 886 rectal cancer, 4,765 controls). Use of olive oil in frying demonstrated a positive effect in colon cancer risk reduction but not in rectal cancer.55
The relative safety of olive oil and the availability of randomized clinical trials in humans render data from animal trials mostly irrelevant.
The use of olive oil as a nutritional source in intensive care and high-risk surgery patients and in neonates has been studied. Olive oil is well tolerated, and decreases in intensive care unit stay and infection rates have been demonstrated in surgical patients.56, 57, 58 In preterm infants, olive oil has been compared with soybean oil or usual parenteral nutrition. Trials are generally small; however, olive oil supplementation appears to be safe and well tolerated and achieves the targeted essential fatty acid and lipid profiles. However, effects on LDL oxidation and immune status are equivocal.59, 60, 61, 62, 63
Applied topically, olive oil acts as a demulcent and emollient. It is used in massage and to soften the skin in eczema and psoriasis, as well as to prevent stretch marks. Olive oil is used in the preparation of soaps, ointments, and liniments.3 A clinical study of virgin olive oil and virgin coconut oil found both oils to be effective in reducing dermatitis symptoms.70 In preterm infants, 4 weeks of daily olive oil-based cream was more effective than an emollient with regard to dermatitis.71
Because fat has been shown to effect postprandial glycemic response, a randomized crossover interventional study was conducted in 13 patients with type 1 diabetes to determine if the type and amount of dietary fat as well as the glycemic index of a meal may affect postprandial glucose. Each intervention comprised 3 high-glycemic test meals over a 7-day period and then crossed over to 3 low-glycemic test meals. Data from the 12 patients who completed the study revealed that the glycemic index of meals significantly delayed the time to peak glucose; 156 min vs 253 min (P=0.003) for low- and high-glycemic index meals, respectively, but did not significantly affect peak glucose levels. In this context, a highly significant effect on glycemic response was seen with the type of fats given with high-glycemic index meals but not low (P<0.0001). Mean postprandial blood glucose levels within the first 3 hours after the test meals were statistically and clinically significantly lower (P<0.05) with fat provided by 37 g extra-virgin olive oil (EVOO; 198 mmol/L) than with 43 g butter (398 mmol/L) or by the low-fat meal (416 mmol/L). Additionally, the minimum time to peak glucose levels was significantly delayed in high-glycemic meals after EVOO compared to butter or the low-fat meal (P=0.035). With high-glycemic meals, the mean times to peak blood glucose for types of fats were EVOO 190 minutes, low-fat meal 146 minutes and butter 133 minutes compared to a range of 234 to 265 minutes seen when these fats were given with low-glycemic meals (P=0.003). These data suggest that the type of fat has a more significant effect on glycemic response in patients with type 1 diabetes than the amount of fat.91
As a component of medical nutrition therapy for patients with type 2 diabetes, the American Diabetes Association Standards of Care (2014) recommend higher quality dietary fat intake, as an alternative to decreased fat intake, by replacing saturated and/or trans fats with mono- and poly-unsaturated fatty acids in the diet. This Mediterranean-style approach to eating may improve glycemic control and cardiovascular disease risk factors (moderate-quality evidence).81
Olive oil is a mild laxative and has been used as an intestinal lubricant.64, 72 There are claims that it is useful for gall bladder problems, including cholecystitis and cholelithiasis; however, the effectiveness of olive oil for such conditions is not well documented.73 Olive oil retention enema has been used to relieve constipation.80 Effects of olive oil and flaxseed oil, compared with mineral oil, were evaluated in 50 adult hemodialysis patients with constipation. Initial doses of oils were 4 mL/day and adjusted as needed over the 4-week study period; 82% of patients on flaxseed oil required adjustments compared with 69% for olive oil (average final dose, 5.7 ± 2.5 mL/day) and 53% for mineral oils. Rome III scores improved significantly with each of the 3 oil treatments (P < 0.01 for each). Flaxseed oil yielded improvements only in the frequency and consistency of stools, whereas mineral and olive oils improved scores in 5 of the 6 total constipation symptoms. Diabetic nephropathy, hypertensive nephrosclerosis, glomerulonephritis, and polycystic kidney disease were the main etiologies that led to chronic kidney disease.86
The American College of Rheumatology guidelines on the management of gout (2012) voted that the use of various oral complementary agents, including olive oil, was inappropriate for the treatment of an acute attack of gout.76
Olive oil has been 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.74
It is used as a vehicle for oily suspensions for injection and is a drug solvent; it has also been used to soften ear wax.3, 64 In elderly patients, it has been used in cognitive function clinical trials, as well as in studies of rheumatoid arthritis as the comparator (placebo) oil.65, 66
Trials investigating the effects of olive oil have typically used daily doses ranging from 2518 to 40 mL25 and 850 to 70 g24 without reported adverse reactions. It has also been used topically to soften ear wax and incorporated into creams for topical application.71, 73 When administered as a retention enema for constipation, a volume of 100 to 250 mL has been used.80
Pregnancy / Lactation
GRAS status when used as food. Avoid dosages above those found in food because safety and efficacy are unproven. A clinical study used daily olive oil (4 g) as a comparator oil in pregnant women at 30 weeks gestation and followed them through to delivery. Olive oil was assumed to be inert and no adverse events were reported at this dose.75
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.73 Use as a retention enema may cause fecal incontinence, or mechanical trauma.80
Information is lacking.
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