By Craig Weatherby
Olives and extra virgin olive oil feature rare antioxidants called tyrosol esters.
This family of polyphenol compounds is nearly unique to olives and extra virgin olive oil (EVOO).
It’s more accurate to put “antioxidants” in quotes when referring to the polyphenols (and carotenoids) in whole plant foods.
While these food factors deliver well-documented health benefits, they don’t exert direct antioxidant effects in the body. (See our sidebar, “The gene effects of ‘antioxidants’ in plant foods”.)
Recent research virtually proves that olives and EVOO rank among the healthiest plant foods, with special benefits for artery health.
As the authors of an evidence review wrote earlier this year, “For some [cardiovascular] activities of olive oil phenolic compounds, the evidence is already strong enough to enable the legal use of health claims on foods.” (Martín-Peláez S et al. 2013).
To see our coverage of selected research reports, visit the Olive Oil & Other Oils section of our news archive.
Beyond cardiovascular health, the rare tyrosol compounds in olives and EVOO also appear to benefit the brain.
The gene effects of “antioxidants” in plant foods
The polyphenol and carotenoid compounds in whole plant foods are commonly called “antioxidants” because they behave that way in test tube experiments.
But in general, these health allies do not exert direct antioxidant effects in the body… at least not to a very substantial extent.
Instead, polyphenols appear to exert strong indirect effects on oxidation and inflammation via so-called “nutrigenomic” effects on gene switches (e.g., transcription factors) in our cells.
Polyphenols’ nutrigenomic effects tend to moderate inflammation and stimulate the body’s own antioxidant network … which includes enzymes, lipoic acid, CoQ10, melatonin, and vitamins C and E.
The richest known food source of polyphenols are raw (non-alkalized / non-“Dutched”) cocoa, berries, plums, prunes, tea, coffee, extra virgin olive oil, beans, and whole grains.
(Highly beneficial procyanidin-type polyphenols abound in cocoa, dark-hued berries – e.g., blackberries, blueberries açaí berries – grapes, red wine, and tea. Comparably beneficial anthocyanin-type polyphenols abound in cherries and most berries.)
Extra virgin olive oil is uniquely rich in hydroxytyrosol, oleuropein, oleocanthal, and other tyrosol esters … a particularly potent class of polyphenols with clinically documented vascular and brain benefits.
Growing evidence of olives’ brain benefits
We covered some early animal research on this topic five years ago, in “Antioxidant Unique to Extra Virgin Olive Oil Protects Mouse Brain Cells”.
A growing body of animal research affirms these brain benefits (Pitozzi V et al. 2012), while clinical and population studies have linked olives and EVOO to human brain health.
For example, oleocanthal – a polyphenol in olives and EVOO – has been linked to reduced risk of Alzheimer's disease, while oleocanthal enhances clearance of brain-damaging amyloid protein (Abuznait AH et al. 2012).
And several population studies have linked Mediterranean diets high in olive oil polyphenols to reduced risk of dementia (Misirli G et al. 2012).
As a Spanish team wrote last year, “Increased consumption of antioxidant-rich foods in general and of polyphenols in particular is associated with better cognitive performance in elderly subjects … the results reinforce the notion that Mediterranean diet components might counteract age-related cognitive decline.” (Valls-Pedret C et al. 2012)
Now, Italian scientists report their discovery of another way in which olives’ rare antioxidants protect and enhance animals’ brain functions … and likely benefit human brains as well.
Study detects a new brain benefit from EVOO
A team from Italy’s Institute of Cell Biology and Neurobiology report that olive polyphenols may benefit brains in previously unsuspected ways (De Nicoló S et al. 2013).
Specifically, results seen in mice suggest that certain tyrosol compounds in olives raised levels of key proteins in the brain.
The Italian team, led by Dr. Marco Fiore, divided 12 mice into two groups for a 10-day study.
Six mice got regular chow, while six got chow fortified with an extract of olive “pomace” ... the polyphenol-rich oil from the first pressing of olive pulp. The experimental chow contained 10 mg per kg of olive polyphenols.
After 10 days, the brains of the group fed chow containing the polyphenol-rich olive extract had higher levels of two kinds of “neurotrophin” proteins:
Nerve growth factor (NGF)
Brain-derived neurotrophic factor (BDNF)
Thanks to their key roles in the development, growth, and survival of brain cells, NGF and BDNF are considered critical to critical to learning and memory.
As the Italian team wrote, “Polyphenols extracted from olive may increase the levels of NGF and BDNF in … brain areas playing a key role in learning and memory processes …” (De Nicoló S et al. 2013).
Levels of NGF and BDNF and “expression” of their respective cell receptors (TrkA and TrkB) rose in the hippocampus and olfactory bulbs and fell in the frontal cortex and striatum.
In short, the olive extract did very good things with regard to the animals’ capacity of learning and memory.
Abuznait AH, Qosa H, Busnena BA, El Sayed KA, Kaddoumi A. Olive-Oil-Derived Oleocanthal Enhances β-Amyloid Clearance as a Potential Neuroprotective Mechanism against Alzheimer's Disease: In Vitro and in Vivo Studies. ACS Chem Neurosci. 2013 Feb 25. [Epub ahead of print]
De Nicoló S, Tarani L, Ceccanti M, Maldini M, Natella F, Vania A, Chaldakov GN, Fiore M. Effects of olive polyphenols administration on nerve growth factor and brain-derived neurotrophic factor in the mouse brain. Nutrition. 2013 Apr;29(4):681-7. doi: 10.1016/j.nut.2012.11.007.
Diomede L, Rigacci S, Romeo M, Stefani M, Salmona M. Oleuropein Aglycone Protects Transgenic C. elegans Strains Expressing Aβ42 by Reducing Plaque Load and Motor Deficit. PLoS One. 2013;8(3):e58893. doi: 10.1371/journal.pone.0058893. Epub 2013 Mar 8.
Lou-Bonafonte JM, Arnal C, Navarro MA, Osada J. Efficacy of bioactive compounds from extra virgin olive oil to modulate atherosclerosis development. Mol Nutr Food Res. 2012 Jul;56(7):1043-57. doi: 10.1002/mnfr.201100668. Review.
Lou-Bonafonte JM, Fitó M, Covas MI, Farràs M, Osada J. HDL-related mechanisms of olive oil protection in cardiovascular disease. Curr Vasc Pharmacol. 2012 Jul;10(4):392-409. Review.
Martín-Peláez S, Covas MI, Fitó M, Kušar A, Pravst I. Health effects of olive oil polyphenols: Recent advances and possibilities for the use of health claims. Mol Nutr Food Res. 2013 May;57(5):760-71. doi: 10.1002/mnfr.201200421. Epub 2013 Mar 1.
Misirli G, Benetou V, Lagiou P, Bamia C, Trichopoulos D, Trichopoulou A. Relation of the traditional Mediterranean diet to cerebrovascular disease in a Mediterranean population. Am J Epidemiol. 2012 Dec 15;176(12):1185-92. doi: 10.1093/aje/kws205. Epub 2012 Nov 27.
Pitozzi V, Jacomelli M, Catelan D, Servili M, Taticchi A, Biggeri A, Dolara P, Giovannelli L. Long-term dietary extra-virgin olive oil rich in polyphenols reverses age-related dysfunctions in motor coordination and contextual memory in mice: role of oxidative stress. Rejuvenation Res. 2012 Dec;15(6):601-12. doi: 10.1089/rej.2012.1346. Epub 2012 Nov 16.
Urpi-Sarda M, Casas R, Chiva-Blanch G, Romero-Mamani ES, Valderas-Martínez P, Arranz S, Andres-Lacueva C, Llorach R, Medina-Remón A, Lamuela-Raventos RM, Estruch R. Virgin olive oil and nuts as key foods of the Mediterranean diet effects on inflammatory biomakers related to atherosclerosis. Pharmacol Res. 2012 Jun;65(6):577-83. doi: 10.1016/j.phrs.2012.03.006. Epub 2012 Mar 18. Review.
Valls-Pedret C, Lamuela-Raventós RM, Medina-Remón A, Quintana M, Corella D, Pintó X, Martínez-González MÁ, Estruch R, Ros E. Polyphenol-rich foods in the Mediterranean diet are associated with better cognitive function in elderly subjects at high cardiovascular risk. J Alzheimers Dis. 2012;29(4):773-82. doi: 10.3233/JAD-2012-111799.