Let me introduce you to Olea europaea. Have you met? I’m certain you have.
Common names include European olive, African olive, or just plain olive. There are hundreds of cultivars of Olea europaea, but luckily for this post (and its author!), they all have the same basic characteristics and benefits.
Olea europaea is native to the eastern Mediterranean region. There is evidence that olives were cultivated for food on Crete in 3500 BCE.1 We know the ancient Egyptians used olive branches in religious practices, the ancient Greeks used them on occasions of birth, death, marriage and victory, and the ancient Romans used them to signify peace.2 Olive also appears in the Quran and the Bible – most notably when a dove brings Noah an olive branch after the Great Flood.
So olive trees and people have a long history, but some individual olive trees have a long history all of their own – they can live for over 1,000 years!2 A fully-grown tree can be anywhere from 3 to 12 metres, and the wood of the trunk and branches is tough. It resists decay and can even grow a new trunk out of old roots if the original one is lost!1 The leaves are opposite, with short stalks, and they are rough and leathery to the touch. They are dark green on top and almost silver underneath.
As we’ve already mentioned, olive trees give us an abundance of great gifts (see the first image). Let’s take a closer look.
We all know olive oil is good for us, but why? The answer is polyphenols! Polyphenols are a group of over 8,0003 compounds that include all the good stuff we hear about – flavonoids, phenolic acids and lignans, for example. Plants have them to protect themselves against ultraviolet radiation and/or pathogens, but they’re good for us too.4 They’re the reason fruit, veggies, green tea, red wine and dark chocolate have so many health benefits. Polyphenols have excellent antioxidant properties. Some also have anti-allergic, anti-inflammatory and anti-thrombotic effects, among other things, which makes them great support for the immune system, and a possible line of defence against cardiovascular disease, cancers, diabetes, osteoporosis and degenerative neurological disease.3,5
The polyphenol content of olive oil can be between 50 and 1,000 mg/kg. The content depends on the extraction method, how the olives were grown and the type.5 The amount of polyphenols can also be affected by heat. So, when you cook with olive oil, the health benefits will be reduced in comparison to sloshing it ‘raw’ on your Greek salad. However, all (polyphenol content) is not lost! A 2020 scientific study on extra virgin olive oil showed that, although polyphenols are reduced by 40% at 120°C and up to 75% at 170°C, cooked olive oil is still good for us!5 One of the authors of the study, Julián Lozano-Castellón, said, “Despite the decrease in concentration of polyphenols during the cooking process, this oil has a polyphenol level that reaches the declaration of health in accordance to the European regulation, which means it has properties that protect oxidation of LDL cholesterol particles.”6 So no need to quit the fasolada – phew!
As olive oil comes from olives, you can imagine olives have the same fantastic polyphenols in them. The only problem is that olives straight off the tree are really, really bitter and, frankly, you don’t want to think about eating them. They must be processed to remove the oleuropein and phenols that cause the bitterness.7 The only problem is that it’s these compounds that have the major health benefits. However, there is still plenty of good stuff left in processed olives after they are cured. It’s true they also have a high salt content after curing, though, so go easy on the olives!
Yes, leaves! The leaves of the olive tree are packed with amazing compounds too – monoterpenes like oleuropein, flavonoids, triterpenoids and hydroxytyrosol, a compound which many of the health benefits of olive are associated with.2 So what does olive leaf do? (This is always my husband’s question when I start working with a new plant.) As far as olive leaf is concerned, the answer is a lot.
Part of the Hippocratic Corpus from the 5th century BCE mentions using the leaf to support heavy menstrual bleeding. It was also used in the ancient world until the Renaissance, and in parts of Africa, to help wounds stop bleeding (styptic action), to help them heal (vulnerary action) and stop infection.2 Olive leaf was used in Iran and Iraq against coughs and as a disinfectant, and in Yemen, where it was used as support for colds. Olive leaf’s reputation as a line of defence against infections and viruses is borne up by modern science – olive leaf is indeed antimicrobial, and oleuropein has been proven to have antiviral actions too. It is patented in the USA for several viruses in humans and animals.8
Proof that olive leaf is a vulnerary is a lot more scanty. Although it has been used as such for thousands of years traditionally, there haven’t been sufficient scientific studies to prove this property of the leaf.
Olive leaf is also anti-inflammatory, thanks to the phenolic compound hydroxytyrosol2. It could therefore be helpful in cases of arthritis (on which clinical studies have been done) and possibly even osteoporosis (where more research is needed). Clinical trials have also shown promising results when using olive leaf extract to support diabetes9 and lower blood pressure.10
So I think we can agree that olive leaves sound pretty amazing, can’t we? However, you don’t want to eat olive leaves. I imagine eating one would be a bit like chewing leather. I also imagine that cooking them wouldn’t help – that would probably be like chewing warm leather! But there are a few simple ways to get all that olive leaf goodness into your body: tincture or infusion. In my next post, you can join me on my Adventures with Olive and see how I make these remedies, and how I’m preserving our olives this year.
1 Olive, Encyclopeadia Britannica, the Editors of Encyclopaedia Britannica, May 2019, https://www.britannica.com/plant/olive-plant
2 Olive Leaf Monograph from The Herbarium by the Herbal Academy
3 Potential Health Benefits of Olive Oil and Plant Polyphenols, Gorzynik-Dębicka et al., International Journal of Molecular Science, 2018 Mar; 19(3): 686. doi: 10.3390/ijms19030686
4 Plant polyphenols as dietary antioxidants in human health and disease, Pandey and Rizvi, Oxidative Medicine and Cellular Longevity 2009 Nov-Dec; 2(5): 270–278 doi: 10.4161/oxim.2.5.9498
5 Domestic Sautéing with EVOO: Change in the Phenolic Profile, Lozano-Castellón et al., Antioxidants 2020 Jan; 9(1): 77 doi: 10.3390/antiox9010077
6 Does olive oil lose its health benefits when heated? Dr Ananya Mandal, News Medical, 1st March 2020, https://www.news-medical.net/news/20200301/Does-olive-oil-lose-its-health-benefits-when-heated.aspx
8 The Liver: Oxidative Stress and Dietary Antioxidants (2018), Seung K. Yoon
9 Olive (Olea europaea L.) Leaf Polyphenols Improve Insulin Sensitivity in Middle-Aged Overweight Men: A Randomized, Placebo-Controlled, Crossover Trial, de Bock et al., Plos Climate 2013 March doi: 10.1371/journal.pone.0057622
10 Food supplementation with an olive (Olea europaea L.) leaf extract reduces blood pressure in borderline hypertensive monozygotic twins, Perrinjaquet-Moccetti et al., Phytotherapy Research 2008 August doi: 10.1002/ptr.2455