Olives and olive oil in cancer prevention
I don’t know about you, but I love using olive oil for cooking and I enjoy olives too, either as a snack or an ingredient in recipes. So, it’s wonderful to know that they’re doing me good at the same time. Let’s look at how that works.
Extra virgin olive oil and cancer
A recent systematic review looked at 45 studies that investigated the link between EVOO and cancer prevention. In total, this covered over 1 million people. They did a meta-analysis, which involves pooling the numbers from all of the studies, and found that those who had the highest consumption of olive oil had a 31% lower risk of any cancer (1).
The risk of breast cancer was 33% lower (1).
Gastrointestinal cancer risk was 23% lower. The effects were most pronounced for oesophageal and pancreatic cancers, but were also found in gastric cancers and, to a lesser extent, colorectal cancers (1).
Upper aerodigestive cancer risk was reduced by 22%. It was most effective on nasopharyngeal and laryngeal cancers, with oral/pharyngeal and all other upper aerodigestive cancers also having a lower risk (1).
Risk of urinary tract cancers was reduced by 54%. This included an impressive effect on bladder and prostate cancers (1).
The interesting part about this review and meta-analysis was that people were taken from both Mediterranean and non-Mediterranean populations. That suggests that it isn’t other elements of the Mediterranean diet that affect these cancer risk figures but the olive oil itself.
Extra virgin olive oil and breast cancer
One of the common tests for those who have breast cancer in particular is the HER2 test. HER2 is a protein that is found on the outside of cells. In normal cells, it helps control cell growth. But cancer cells can make too much HER2, called HER2 positive, and that’s associated with faster growth and metastasis (2). Actually, HER2 positive cancers aren’t confined to breast cancer; pancreatic, bladder, stomach and ovarian cancers can also be HER2 positive.
Rats that had breast cancer were fed a diet high in olive oil. They had lower levels of HER2 and their tumours were less malignant than those who didn’t have the olive oil (3). Scientists have found that it is the oleic acid in olive oil that suppresses HER2 (3).
In vitro tests on human breast cancer cell lines that are often HER2 positive showed that olive oil almost halved their HER2 levels, almost comparable to Herceptin®, which is used to treat HER2 positive metastatic breast cancer (3).
EVOO also improves the performance of aromatase inhibitors, which are often used during treatment for hormone-sensitive cancers (4).
Extra virgin olive oil is anti-inflammatory
Extra virgin olive oil (EVOO) is mainly made up of a monounsaturated fat called oleic acid. Most seed oils, like sunflower, safflower and canola (rapeseed), contain high levels of omega 6 fatty acids, which are inflammatory. Oleic acid, on the other hand, is anti-inflammatory and contains a balance of omegas 9, 6 and 3 fatty acids (5).
EVOO is also full of antioxidants in the form of polyphenols, with some vitamin E and K. Two of the polyphenols, oleocanthal and oleacein, are of particular interest if you want to fight cancer. Oleocanthal has been compared to ibuprofen, a non-steroidal anti-inflammatory drug, as it’s anti-inflammatory using the same COX inhibiting pathway. Scientists have found that 50g per day of EVOO that is high in oleocanthal is equivalent to about 10% of a normal dose of ibuprofen (6).
This might not sound like enough to have any effect, but remember that low doses of aspirin, another COX inhibitor, are used for the cardiovascular benefits (6). Ibuprofen is similarly used to prevent blood clotting, to reduce the risk of some cancers, and even to treat mice with Alzheimer’s (6).
You might have noticed that a good quality olive oil stings your throat slightly as you swallow it. That is thought to be the effect of oleocanthal. So, if you want to find a good olive oil, look for that stinging effect and it will be high in oleocanthal (6).
If you’ve read my book, you’ll know that inflammation is believed to be the source of most cancers, so reducing it is crucial to fighting it and preventing its formation and recurrence.
Mechanism of olive oil’s cancer-fighting
It is the oleocanthal that kills cancer cells and scientists know how this works. Within each cell are structures called lysosomes, where the cell stores waste. The membranes of the lysosomes in cancer cells seems to be weaker than those in normal cells. When the cancerous cells are exposed to oleocanthal, the lysosomes’ membranes break and release the waste into the cell. That causes the cancer cells to die within 30 minutes to an hour. Non-cancerous cells aren’t affected (7).
Olive oil and stomach cancer
One of the causes of stomach cancer, along with gastritis and stomach ulcers, is infection with Helicobacter pylori.
A couple of small studies showed that the phenolic compounds in EVOO helped to kill the bacteria. The dosage used was 30g, about 2 tablespoons (8). It didn’t completely eradicate the bacteria, but the usual treatment is a combination of 3 antibiotics because none of them is completely effective alone either. The usual combination is becoming less effective because of antibiotic resistance too (8). Given this, taking EVOO as well as the combination antibiotic therapy might be a way to get rid of the infection and reducing your cancer risk.
Olive oil and leukaemia
One of the most impressive studies on the use of EVOO in cancer was a small randomised trial on patients with early-stage Chronic Lymphocytic Leukaemia (CLL). They weren’t receiving any other treatment, but were on a Watch and Wait program. They were split into 2 groups: one received 40 ml a day of high oleocanthal and high oleacein (OC/OL) EVOO and the other received 40 ml a day of low OC/OL. After 3 months, the group on high OC/OL had improved blood markers (9).
About 9-12 months following this, another group, including some of the original high OC/OL patients, were given 40 ml a day of high OC/OL EVOO for 6 months. They were then tested for white blood count and measures of apoptosis, a form of programmed cell death that cancer cells don’t show. Apoptosis is a form of cell death that doesn’t leave a lot of rubbish behind that can damage the body. This is unlike necrosis, which is how most cancer treatments kill cancer cells. After 6 months, the white blood count, which is generally high in CLL, was significantly reduced. And the markers for apoptosis were significantly increased, suggesting that the cancer cells were dying (9).
Olive oil and weight gain
You might well be thinking that taking 40 ml a day of olive oil would make you put on weight. As you probably know, being overweight raises your risk of many cancers. But it seems that it doesn’t cause weight gain.
A large study looked at the diets of 7,368 Spanish university graduates and examined the differences between those who had the highest consumption of EVOO (46 g/day) and the lowest (6 g/day) over 28 months. Amazingly, the group with the highest consumption of EVOO was associated with a lower incidence of weight gain (10).
Is olive oil safe to cook with?
You might have heard that you shouldn’t cook with olive oil because it has a relatively low smoke point compared with other oils, such as soybean, safflower sunflower and palm oil. The thinking is that when oils are heated to their smoke point, it causes oxidation of the oil, which can produce carcinogenic substances.
EVOO’s antioxidant compounds help to prevent oxidation (11). That makes it safer than other oils for frying and cooking with, despite it relatively low smoke point.
Having said that, oleocanthal does degrade with heat to some extent, so it’s worth using EVOO uncooked for its anticancer effects. It works well in dressings, mayonnaise, marinades and on bruschetta, baked potatoes and other cooked vegetables. The latter is particularly good because the addition of fat to vegetables that contain the fat-soluble vitamins (vitamin A, D, E and K) helps your body to absorb the vitamins more easily.
What makes a good quality olive oil?
Always look for Extra Virgin olive oil. The ones that aren’t extra virgin may be adulterated with other oils. They will be more refined and they won’t contain the same levels of antioxidants and polyphenols as EVOO.
Check for a third party certification seal. Italy’s DOP, the European Union’s Protected Designation of Origin (PDO) or the Californian Olive Oil Council’s ‘COOC Certified Extra Virgin’ all confirm a good quality oil. Those made in Chile and Australia are always worth buying too. Australia has the highest standards of olive oil production and neither country mixes in oil from the previous year’s harvest.
EVOO that is labelled ‘Light’ has a milder flavour. It doesn’t correspond to lower calories or to its colour.
Always buy your EVOO in a coloured glass bottle and store it somewhere dark and cool. Light and heat cause it to degrade. Oleocanthal in particular breaks down at higher temperatures (12).
Check the bottle to see whether it shows the date of harvest or the date of pressing. The best companies’ oils do. Although the Use by Date is helpful to some extent, it can be based on 18 months from the date of bottling, which could be significantly later than when it was harvested. You want the freshest oil that you can buy, because the longer it’s stored, the less beneficial it is. That applies to storage at home too. Don’t buy a bigger bottle than you’re likely to use within 4-6 weeks of opening it.
Although you can’t tell this until you’ve bought and tried it, remember that the more peppery the taste the higher the levels of oleocanthal.
If it tastes rancid, throw it out and avoid that brand in future.
If you’re unsure whether the oil you’ve bought is pure olive oil, check it by decanting a small amount into a clean jar and refrigerate it. If it goes solid, it’s pure olive oil. Polyunsaturated oils will stay liquid.
Conclusion
I hope that this article has persuaded you to throw out your seed oils and replace them with EVOO. Olives themselves also contain the useful polyphenols, antioxidants and vitamins, so don’t overlook them. Unless, of course, you hate olives 😊
If this article has helped you, please share it with your friends, especially those who have or have had cancer.
You’ll also find other helpful blog posts on my website, and a lot more information about diet, lifestyle, supplements and herbs that can help prevent cancer formation and recurrence in my book. To find links to all the online stores that stock the book, in both paperback and ebook formats, click on the ‘Buy the book’ button below.
References
Markellos C, Ourailidou M-E, Gavriatopoulou M, Halvatsiosis P, Sergentanis TN, Psaltopoulou T. Olive oil intake and cancer risk: A systematic review and meta-analysis. PLoS One. 2022;17(1):e0261649. doi:10.1371/journal.pone.0261649
National Cancer Institute. NCI Dictionary of Cancer terms. National Cancer Institute. https://www.cancer.gov/publications/dictionaries/cancer-terms/def/her2-positive. Accessed February 14, 2023.
Menendez J, Lupu R. Mediterranean dietary traditions for the molecular treatment of human cancer: Anti-oncogenic actions of the main olive oils monounsaturated fatty acid oleic acid (18:1N-9). Current Pharmaceutical Biotechnology. 2006;7(6):495-502. doi:10.2174/138920106779116900
Ismail AM, In LLA, Tasyriq M, et al. Extra virgin olive oil potentiates the effects of aromatase inhibitors via glutathione depletion in estrogen receptor-positive human breast cancer (MCF-7) cells. Food and Chemical Toxicology. 2013;62:817-824. doi:10.1016/j.fct.2013.10.024
Basu A, Devaraj S, Jialal I. Dietary factors that promote or retard inflammation. Arteriosclerosis, Thrombosis, and Vascular Biology. 2006;26(5):995-1001. doi:10.1161/01.atv.0000214295.86079.d1
Beauchamp GK, Keast RS, Morel D, et al. Ibuprofen-like activity in extra-virgin olive oil. Nature. 2005;437(7055):45-46. doi:10.1038/437045a
Taylor & Francis Group Ltd. Olive oil: The key to curing cancer? Bionity.com. https://www.bionity.com/en/news/151908/olive-oil-the-key-to-curing-cancer.html. Published March 4, 2015. Accessed February 14, 2023.
Castro M, Romero C, de Castro A, et al. Assessment of helicobacter pylori eradication by Virgin Olive Oil. Helicobacter. 2012;17(4):305-311. doi:10.1111/j.1523-5378.2012.00949.x
Gil APR, Kodonis I, Ioannidis A, et al. The effect of dietary intervention with high-oleocanthal and Oleacein olive oil in patients with early-stage chronic lymphocytic leukemia: A pilot randomized trial. Frontiers in Oncology. 2021;11:801249. doi:10.3389/fonc.2021.810249
Bes-Rastrollo M, Sánchez-Villegas A, de la Fuente C, de Irala J, Martínez JA, Martínez-González MA. Olive oil consumption and weight change: The Sun Prospective Cohort Study. Lipids. 2006;41(3):249-256. doi:10.1007/s11745-006-5094-6
Lozano-Castellón J, de Alvarenga JFR, Vallverdú-Queralt A, Lamuela-Raventós RM. Cooking with extra-virgin olive oil: A mixture of food components to prevent oxidation and degradation. Trends in Food Science & Technology. 2022;123:28-36. doi:10.1016/j.tifs.2022.02.022
Salsano JE, Digiacomo M, Cuffaro D, Bertini S, Macchia M. Content variations in oleocanthalic acid and other phenolic compounds in extra-virgin olive oil during storage. Foods. 2022;11(9):1354. doi:10.3390/foods11091354
