More research is needed - but the evidence to date suggests that olive oil has a number of health benefits and (provided it is uncooked) no health risks.

Likely to help protect against coronary heart disease: As the Mayo Clinic explains olive oil contains healthy monounsaturated fatty acids, which may lower your total cholesterol and low-density lipoprotein cholesterol levels, may help normalize blood clotting and may also benefit insulin levels and blood sugar control.

Much of the evidence here is epidemiological (with olive oil a recurring ingredient in the Mediterranean diet, which is associated with lower levels of coronary heart disease).

Further evidence includes laboratory research led by Fatima Paiva-Martins at the University of Porto and published in Molecular Nutrition & Food Research – which suggested that DHPEA-EDA, a major antioxidant in olive oil, is particularly effective at protecting red blood cells from damage and thereby reducing the risk of heart disease caused by reactive oxidation. And a small scale clinical trial in Spain, among 21 volunteers with high cholesterol, suggested that extra virgin olive oil, which has a high phenol content (with anti-inflammatory, antioxidant and clot-preventing properties) improved blood vessel response and function. This was reported in the Journal of the American College of Cardiology.    

This also correlates with research reported by the British Heart Foundation in 2010, which suggested that the phenols in olive oil ‘dampen down’ genes that can cause inflammation in the body, which in turn can increase the risk of cardiovascular disease.

Likely to help protect against cancer. Epidemiological evidence also suggests that the Mediterranean diet, of which olive oil is an important part, has protective effects against cancer. Research by Owen et al in 2000 suggested that high consumption of extra virgin olive oils, which are particularly rich in phenolic antioxidants, could afford considerable protection against colon, breast and skin cancer.

Likely to protect against ulcerative colitis and peptic ulcers. A study of over 25,000 people between the ages of 40 and 65 in Norfolk (UK), led by Dr Andrew Hart of the UEA’s School of Medicine found that participants with the highest intake of oleic acid (found in abundance in olive oil) had a 90% lower risk of developing ulcerative colitis. Meanwhile, in laboratory experiments by Brenes et al at Valme University Hospital in Seville under simulated conditions phenolic compounds in extra virgin olive oil had a strong antibacterial effect against eight strains of H.pylori (which can cause gastritis and peptic ulcer disease) including antibiotic resistant strains.

Protective against liver damage: Mohamed Hammami from the University of Monastir, writing in BioMed Central’s open access journal, Nutrition and Metabolism reported that, in experiments with rats, a diet containing olive oil provided partial protection from liver damage resulting from exposure to a moderately toxic herbicide known to deplete antioxidants and cause oxidative stress – although he went on to say more detailed studies would be needed to substantiate these initial findings.

Possibly protective against Alzheimer’s: Laboratory research at the Monell Center and Northwestern University suggests that oleocanthal, found in olive oil, can alter the structure of neurotoxic proteins believed to contribute to the debilitating effects of Alzheimer’s (Breslin and Klein). Clinical trials would be needed to ascertain how effective this would be likely to prove in practice.

Few health risks appear to have been identified thusfar – other than noting that olive oil is best consumed uncooked and that if cooked at high temperatures it could become unstable and possibly increase the risk of heart disease.

In conclusion:

  • More research is needed, in particular from clinical trials.
  • However, no significant health risks appear to have been identified as regards uncooked olive oil.
  • Conversely, the evidence to date suggests olive oil is an important component in the Mediterranean diet, likely to have a number of protective health benefits. 

Published 19/05/2011, Review date August 2014