The Potential Health Benefits of Antioxidants from Olive Oil
One of the key components of the heart-healthy Mediterranean Diet is olive oil. Like other vegetable oils, olive oil contains a high proportion of healthy fats. However, the antioxidant content of particularly the extra virgin olive oils is suspected to convey an additional health benefit.
Olives naturally contain a high content of oil: about 11% of the weight. The oil is made by grinding whole olives and using a press or centrifuge to extract the oil from the vegetable matter and water. Of the various grades of olive oil, refined and extra virgin are most often found in the supermarket. Refined olive oil receives extra processing and is yellow, with low flavor and aroma. Extra virgin olive oil is generally green with a peppery flavor and olive-like aroma, and is made only by mechanical processing methods. Virgin olive oils contain higher levels of antioxidants, particularly tyrosol and hydroxytyrosol. For example, Romero and Brenes found that extra virgin olive oils contain 10mg hydroxytyrosol per 100ml, compared to 1 mg hydroxytryrosol per 100 ml in mild olive oil.
Recently, Mateos and co-workers tested the effects of hydroxytyrosol-enriched biscuits on absorption and various oxidation-related parameters in a group of 13 young adults. The study was a double-blind, cross-over, placebo-controlled trial with subjects receiving sweet baked biscuits containing 5mg hydroxytyrosol, or control biscuits without hydroxytyrosol, after an overnight fast. The amount in the enriched biscuits is similar to what is found in around 50g extra-virgin olive oil, which is feasible to obtain from the diet. Blood samples were taken at regular intervals over the following 6 hours, and meals were given 2 and 4 hours after the biscuits were eaten.
The researchers found an immediate increase the metabolites of hydroxytyrosol in the blood and urine of participants. The maximum concentration in the blood plasma was reached within one hour for the 8 metabolites measured, while for the control group, only very low (background) levels were found for a single metabolite. There was no change found in oxygen radical-scavenging (ORAC) or ferric-reducing antioxidant power (FRAP), however there was a significant decrease in the level of oxidized low-density lipoproteins (oxidized-LDL) in the group receiving biscuits with hydroxytyrosol.
The authors found that hydroxytyrosol is bioavailable and quickly taken up into the body after consumption. This agrees with work from Miró-Casas and co-workers, who looked at hydroxytyrosol uptake from olive oil at a similar dose level. The results regarding reduction in oxidized-LDL continues to support the role of extra-virgin olive oil phenolic compounds in promoting heart health, as summarized by Burotta et al., and reflected by the EFSA Scientific Opinion on polyphenols in olive oil. It is thought that reducing the level of oxidized-LDL can help reduce the rate of buildup of plaques in the arteries, thereby promoting heart health.
The study shows that olive oil polyphenols such as hydroxytyrosol can be used in based biscuits, are rapidly absorbed from this food, and have favorable effects on a marker of cardiovascular health.
Mateos R, Martínez-López S, Baeza Arévalo G, Amigo-Benavent M, Sarriá B, Bravo-Clemente L. Hydroxytyrosol in functional hydroxytyrosol-enriched biscuits is highly bioavailable and decreases oxidised low density lipoprotein levels in humans. Food Chemistry 2016, 205, 248-256, http://dx.doi.org/10.1016/j.foodchem.2016.03.011
Bulotta S, Celano M, Lepore SM, Montalcini T, Pujia A & Russo D. (2014). Beneficial effects of the olive oil phenolic components oleuropein and hydroxytyrosol: focus on protection against cardiovascular and metabolic diseases. Journal of Translational Medicine, 12, 219. http://doi.org/10.1186/s12967-014-0219-9
European Food Safety Authority (EFSA). Scientific Opinion on the substantiation of health claims related to polyphenols in olive and protection of LDL particles from oxidative damage (ID 1333, 1638, 1639, 1696, 2865), maintenance of normal blood HDL cholesterol concentrations (ID 1639), maintenance of normal blood pressure (ID 3781), “anti-inflammatory properties” (ID 1882), “contributes to the upper respiratory tract health” (ID 3468), “can help to maintain a normal function of gastrointestinal tract” (3779), and “contributes to body defences against external agents” (ID 3467) pursuant to Article 13(1) of Regulation (EC) No 1924/2006. EFSA Journal 2011;9(4):2033 [25 pp.]. DOI: 10.2903/j.efsa.2011.2033. http://www.efsa.europa.eu/en/efsajournal/pub/2033
Miró-Casas E, Covas M, Fitó M, Farré-Albadalejo M, Marrugat J and de la Torre R. Tyrosol and hydroxytyrosol are absorbed from moderate and sustained doses of virgin olive oil in humans. European Journal of Clinical Nutrition (2003) 57, 186–190. doi:10.1038/sj.ejcn.1601532 http://www.nature.com/ejcn/journal/v57/n1/full/1601532a.html
Romero C, Brenes M. Analysis of total contents of hydroxytyrosol and tyrosol in olive oils. J Agric Food Chem. 2012 Sep 12;60(36):9017-22. doi: 10.1021/jf3026666. Epub 2012 Aug 31. http://www.ncbi.nlm.nih.gov/pubmed/22924436