Many of the beneficial effects on human health were originally thought to be the high concentrations of monounsaturated (omega 9) fatty acids, in particular oleic acid, was considered as the major healthful characteristic of virgin olive oil. Unlike saturated and omega 6 fats these don’t compete with the beneficial omega 3 fatty acids. However, more recent research has shone light on some of the minor ingredients particularly oleuropein (OL) and hydroxytyrosol (HT). There are more than 200 ‘minor components’ in the olive oil, which represent about 2% of the total weight. As a group these are called phenolic compounds (PC) and are found in many sources, however “extra virgin” olive oil, contains among the others, some peculiar phenolic compounds which are not present in other oils and in other foods. The concentration of these PC in olive oil is extremely variable from a few mg/kg up to 800 mg/kg and depend upon different growing and technological aspects of olive oil production 1 and if it is really virgin olive oil. These antioxidant phenolic alcohols also contribute to the long oil shelf-life and influence characteristics including smell and taste (e.g. bitter, astringent, pungent, throat-catching) and color 2. Numerous benefits of these olive oil PC have been shown with cardiovascular, metabolic and neurological diseases, cancer and much more. Truly a health product to add to your daily meals.
When used with vegetables the oils increase the absorption of important antioxidants such as lycopene, the red colour found in tomatoes. Research has found that the way food is cooked can make an enormous difference, especially if it's the colour red. 25 mls of olive oil used in the cooking of about half a kilogram of tomatoes per day, is enough to significantly increase in lycopene levels in plasma by the end of five days compared to just tomatoes alone. When cooking tomato sauce the traditional way in oil the lycopene's leaches out from the tomatoes into the oil because it's very fat soluble. Lycopene protects men from prostate cancer 3.
Olive oils have been found to have particularly high levels of anti-oxidants and anti inflammatory phenolic compounds (PC) and regular consumption of olive oils containing phenols, has the ability to reduce oxidative stress even in those consuming low-antioxidant diets. In one study an increase in olive oil intake resulted in a dose-dependent reduction in oxidative stress and inflammation 4. The most bioactive of these compounds are OL and HT which are released from the olive fruit during the extraction process. In particular, OL is abundant in high amounts in unprocessed olive leaves and fruit, while higher concentration of HT may be found in the fruit and in olive oil 5.
The antioxidant activity of OL and HT which have a high level of bioavailabilty 6 and human studies show that a large proportion of ingested olive oil phenols were absorbed, mainly in the small intestine 7. OL and HT are so effective as they have multiple antioxidant activities. They act as free radical scavengers and radical chain breaking; anti-oxygen radicals; and metal chelators. HT also induces simultaneously both phase II detoxifying enzymes (a set of important enzymes for protecting against oxidative damage) and mitochondrial biogenesis, two critical pathways occurring in the fight against oxidative stress. OL and HT stimulate Nrf2 which increase our body’s own production of antioxidants where they are really needed. This is one of the major reasons they are so beneficial for people with diabetes type 2.
One of the more critical properties of these phenolic compounds is that they may prevent the formation of atherosclerotic plaque, known to cause heart disease or atherosclerosis 8. The olive oil extracts inhibit the oxidation of LDL’s 9. As we have discussed many times in the past LDL cholesterol is not the problem but it becomes a problem when it is oxidized as it is no longer able to fulfil its normal function. In particular, OL, in the average daily intake of olive oil or olive pieces of the Mediterranean diet, remarkably reduced (50% in average) LDL oxidation in fat rich meals (i.e. French fries). OL increased the production of certain anti-oxidative enzymes (glutathione-related enzymes) in preventing oxidation of LDL’s before plaque formation could occur in the artery. In support of this the European Food Safety Authority (EFSA), the equivalent of the FDA in the US and the TGA in Australia and very conservative has officially recognized the protective effects of the olive oil phenolic compounds 10.
Studies in both rabbits and rats have also shown OL has multiple other cardio-protective effects to do with deterioration of the heart muscle (cardiomyopathy) 11. Other interesting properties of olive derivatives including oleanolic acid, ursolic acid and uvaol have shown significant cardiovascular benefits.
In the early 90s scientists first suggested a protective role of OL extracted by olive leaves 12 on diabetes and managing blood sugar. Subsequent studies found a strong link of the anti-diabetic action with the antioxidant effects of OL particularly lowering of blood sugar (hypoglycemic) 13. In diabetic mice, HT significantly decreased fasting glucose, and blood serum levels, the latter effects obtained when treatment with the diabetes drug metformin failed 14. In human studies OL and HT have also been shown to improve insulin action and production in overweight middle-aged men at risk of developing metabolic syndrome (51.1 mg OL, 9.7 mg HT for day). This effect was comparable to that seen with drugs used to treat diabetes 15.
Major epidemiological studies have reported that uptake of olive oil is associated with a reduced risk of cancer in different organs. A meta-analysis published in 2011 summarized the results of 19 studies with 13,800 patients and 23,340 controls showed that high olive oil consumption was associated with a 36% lower risk of developing cancer in breast and a 30% lower risk of developing cancer of the digestive system 16. Both OL and HT have displayed multiple protective effects against cancer, mainly dependent on their antioxidant activity. Although at higher doses, OL and HT may exert pro-oxidant activity 17 responsible for stopping the spread of cancer cells. Olive oil phenols have been shown to inhibit both initiation and promotion/progression phases of cancer development. Among other studies, OL has been shown to inhibit tumor growth and metastases (spreading) human breast cancer transplanted into mice 18. While another compound in olive oil Oleic Acid has been shown to reduce the level of a gene by up to 46% that stimulates cancer cell growth and which occurs in more than 20% of breast cancer patients.
By acting against oxidation and inflammation HT, OL and some of the other derivatives have also been shown to be effective in age-related disorders such as neurodegenerative diseases 19. Supplementation with an olive extract decreased pain and inflammation, and improved the quality of life of people suffering from arthritis. In addition, other studies have shown to lower inflammation-induced bone loss (osteopenia) in rats and found that bone loss was reduced as a result of supplementation 20. HT has also been shown to protect against macular degeneration associated with age-associated macular degeneration. Age-related macular degeneration (AMD) is the leading cause of legal blindness for people over 55 years of age in the Western world 21.
Many studies have reported the protective properties of OL and HT against both bacteria and viral infections 22. Research shows OL to have anti-viral properties including inhibiting HIV-infection and replication 23.
Unfortunately, much of the so-called olive oil sold in stores today is not actually olive oil, but rather a deceptive blend of inferior oils that may or may not include traces of actual olive oil. Both overseas consumer reports and studies have shown as much as 50 percent or more of all the olive oil sold commercially does not pass the stringent testing standards used to qualify the authenticity of real olive oil. Many high-volume, olive oils coming out of Italy and Spain have been shown to contain various blends of other oils and a report in the LA times showed that as much as 69% of imported European olive oil wasn't what it claimed to be. That is why you should by local “Australian” extra virgin olive oil only. It may cost a bit more but you know what you are getting and it is good.
When Hippocrates said “let food be thy medicine”, I have no doubt he was talking about olive oil so add lots more extra virgin olive oil to your food. Try olive oil from the bottle as a substitute for butter. You can apply it directly to the bread, or drizzle it over the salad on your rye bread sandwich.
Mixed with good quality vinegar it becomes a superfood. but more on that later
Some olive oil hints
- Only buy oils in a dark glass bottles.
- Only buy local (Australian) extra virgin olive oil
- Store oils in the fridge or dark, cool places. If heat and sunlight break them down, they’ll form free radicals that damage your body.
- Heating oil makes even the best oil toxic. Cooking with oil destroys many of its nutritional components and causes other toxic components to form. So add oils at the last minute to avoid heating them for too long.
- Cold pressed oils have higher levels of nutrients and toxins are not added or formed during the extraction process.
- Don't worry about colour. Good oils come in all shades, from green to gold to pale straw.
- Ensure that your oil is labelled "extra virgin," since other categories—"pure" or "light" oil, "olive oil" and "olive pomace oil" – have undergone chemical refinement.
- Don’t buy olive oil in a spray can
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- Morello et al 2004
- Fielding et al. 2005
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- Morello et al 2004
- Cicerale et al 2012
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- Nikolas et al 2002
- EFSA J. 2009
- Andreadou 2006
- Gonzalez et al 1992
- Al-Azzawie HF, Alhamdani. 2006
- Cao et al 2014
- de Bock et al 2013
- Psaltopoulou et al. 2011
- Fabiani et al 2009
- Sepporta et al. 2014
- Omar 2010
- Clinical Nutrition 2006
- Liu et al 2007
- Sudjana 2009
- Lee-Huang et al 2003.