Olive oil and breast cancer
October is Breast Cancer Awareness Month.It’s estimated that 1 in 8 women will be diagnosed with breast cancer in her lifetime. While many forms of the disease have a high survival rate, it can still be fatal. This is a month where many organizations take extra time to highlight breast cancer risk factors, screening tools, and treatment options and focus on building community and offering support.
Research on breast cancer has revealed that following a plant-forward Mediterranean-style diet has been shown to be protective. One important thing to note is that, while many associate the Mediterranean diet with drinking wine, studies have shown that even moderate drinking (the equivalent of about one serving of alcohol per day, for women) has been associated with a 7-10% increase in breast cancer risk. Something else many people are not aware of, is that regular consumption of soy in its whole form (think: tofu, tempeh, and edamame) may be protective.
Something else research suggests may be beneficial? Olive oil. Some of the reasons researchers believe it may play a role is because olive oil—in particular extra virgin olive oil (EVOO)—contains several bioactive compounds, such as monounsaturated fatty acids, triterpenes, and polyphenols like phenolic alcohols, secoiridoid, flavonoids, and lignans, which have been associated with anti-inflammatory and antioxidant benefits and possibly even anti-cancer effects.
Here’s what we know so far.
Research in Humans
A 2015 study using data from the PREDIMED study (a 1:1:1 randomized, single-blind, controlled field trial conducted at primary health care centers in Spain in which 4282 women aged 60 to 80 and at high risk for cardiovascular disease were recruited between 2003 and 2009), looked at the effects of diet on risk of invasive breast cancer. In this study looking at breast cancer risk, participants (4152 women from the PREDIMED set with no prior history of breast cancer) were randomly assigned to a Mediterranean diet that was supplemented with extra-virgin olive oil (EVOO), a Mediterranean diet supplemented with mixed nuts, or a control diet. The control diet group participants were advised to reduce take of dietary fat.
After a median follow-up of 4.8 years, the rates of breast cancer incidence (per 1000 people-years) were 2.9 for the control group that had been told to limit fat, 1.8 for the Mediterranean diet with nuts group, and 1.1 for the Mediterranean diet with EVOO group. These results suggest that a Mediterranean diet supplemented with EVOO may help reduce breast cancer risk, but because these results come from a secondary analysis of a previous trial, longer-term and larger studies are needed to confirm.
A 1995 study utilizing food frequency questionnaires given to 820 women with breast cancer and 1548 control women also found that increased intake of EVOO was associated with significantly reduced breast cancer risk after controlling for other risk factors. A 2008 pilot study of Kuwaiti women with stage I breast cancer found lower intake of olive oil to be associated with increased risk of breast cancer. A 2010 meta-analysis of 25 original studies on olive oil and cancer risk found that olive oil intake, compared to other dietary fats, was associated with decreased risk of breast and certain other cancers. A 2019 study in Spain also found that higher total polyphenol intake (possibly from olive oil but perhaps also from other foods) was inversely associated with reduced breast cancer risk only in postmenopausal women.
What components in olive oil provide protection against breast cancer?
Beyond human studies, there are a number of animal model and cell culture studies looking at olive oil and breast cancer and attempting to suggest a mechanism of action
A 2020 review of cell and animal model studies assessed whether olive oil or fish oil have an impact on triple negative breast cancer. They included studies that focused on fish oil ω-3 essential fatty acids docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) and polyphenolic compounds and oleic acid found in olive oil. Oleocanthal in olive oil was found to be associated with decreased tumor proliferation, migration, and invasion as well as decreased tumor volume, decreased tumor latency, and decreased tumor recurrence. Oleanolic acid was associated with decreased tumor migration and with apoptosis and autophagy. Pinoresionl, a lignan found in olive oil, was noted to be associated with cytotoxicity.
A 2019 study in mice found oleocanthal supplementation inhibited proliferation and migration of breast cancer cells. Another mouse study found that oral supplementation with oleocanthal, one of the phenolic compounds in olive oil, was associated with suppression of breast cancer tumor recurrence.
Because endocrine therapy like tamoxifen is often a part of treatment for hormone-driven breast cancers, some studies have also looked at how compounds in certain foods may work synergistically with these medications. A 2017 cell study found that oleocanthal supplementation was associated with suppressing growth of hormone-related breast cancer and with increasing sensitivity to that tamoxifen treatment.
These are just a few more recent studies looking at the effects of compounds found in olive oil on breast cancer. It’s believed by researchers that certain compounds in olive oil may help fight against the spread of breast cancer cells, possibly kill cancer cells, and protect against recurrence.
Applying the Research to Everyday Life
While studies have shown promising results, more research is needed to understand exactly how compounds in olive oil may contribute to decreased risk of breast cancer and the role they may have in the treatment of existing breast cancer.
In the meantime, it’s recommended to follow a plant-forward Mediterranean-style diet and to enjoy olive oil as a primary source of dietary fat for a multitude of health reasons. Other ways to protect against breast and other cancers include maintaining a healthy weight, limiting consumption of red meat, processed meat, alcohol, and added sugars, avoiding smoking, and being physically active.