Use VIRGIN olive oil as your preferred fat to cut risk of breast cancer. Type does matter.

Women who always consume VIRGIN olive oil and use it everyday for cooking may lower their risk of breast cancer, according to a new study we have led from the National Center for Epidemiology at the Instituto de Salud Carlos III in collaboration with the Spanish breast cancer research group: GEICAM.

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In this study in which we were able to differentiate between the type of olive oil consumed and used for cooking, we found that women always using virgin olive oil for cooking and dressing the dishes during the meal,  lowered their risk of developing breast cancer. This protective effect of virgin olive oil was not observed for common (non-virgin) olive oil or for other vegetable oils and it was independent of the other components of the Mediterranean diet. This is important because this dietary pattern, typically consumed among populations bordering the Mediterranean Sea, is characterized by a high intake of olive oil but also fruits, nuts, vegetables, and cereals, together with a moderate intake of fish and poultry and a low intake of dairy products, red meat, processed meats, and sweets. This dietary pattern reduces the risk of heart disease and stroke, and it may also help to prevent breast cancer. In this setting, we hypothesized that olive oil may be a key contributor of this protective effect against breast cancer that the Mediterranean diet appears to provide.

23 hospitals have contributed to the study as part of EpiGEICAM, one of the largest epidemiological studies on breast cancer carried out in Spain with the aim of providing new evidence on the different factors that relate our lifestyle with the appearance of breast cancer. The study has been recently published online in the European Journal of Clinical Nutrition. About a thousand women newly diagnosed with breast cancer were recruited from the oncology services of different hospitals. Each patient was matched with a healthy woman of similar age and living in the same city. In the field of epidemiology, these types of studies are known as matched case-control studies. The study participants, i.e., patients and paired healthy women, were asked about what type and how often they used olive oil in salad dressings, added to food or bread, or in baking and frying. According to the findings, only women always using virgin olive oil for cooking and adding two or more tablespoons of olive oil per day to bread, salad, or their dishes during meals, significantly lowered their risk of developing breast cancer.  This risk reduction was 30 percent, compared to those women not always cooking with olive oil and adding less than 2 tablespoons of olive oil to their dishes during meals. Based on this finding, benefits from olive oil consumption, at least as regards the protection provided for breast cancer, could be only conferred with the virgin version, and when its consumption is at least 2 or more daily tablespoons.

Part of the population continues to perceive olive oil as a very caloric and conflicting food if you want to follow a healthy low-calorie diet. These findings reveal that the amount of olive oil apparently necessary to provide a benefit in breast cancer is modest, being easy to achieve and providing not many calories. In addition, one of the characteristics of virgin olive oil is that with a very small amount it gives a great flavor and palatability to any dish that is added.

While waiting for the main meal, olives are typically served as an appetizer in Spanish restaurants. Picture taken on the island of Formentera (Spain)/Source: CAROLINA DONAT
While waiting for the main meal, olives are typically served as an appetizer in Spanish restaurants. Picture taken on the island of Formentera (Spain)/Source: CAROLINA DONAT

Why is virgin type of olive oil a must?

Olive oil is high in monounsaturated fatty acids, adding up to about 75% by volume, which make it more heat-stable than other seed oils – such as soybean, sunflower, or rapeseed – rich in polyunsaturated fatty acids. This characteristic makes it the preferred fat for cooking. Alongside their fat, olives, also contain more than 200 bioactive compounds, of which polyphenols stand out, with recognized antioxidant and anti-inflammatory properties. The quantity and quality of polyphenols in olive oil is closely related to the process of olive milling and further processing.  Virgin olive oil is obtained by cold pressing of ripe olives, not using heat or chemical additives to extract the oil from the olives. As such, virgin olive oil retains not only the flavors and aromas but also all bioactive compounds such as vitamins, tocopherols, phytosterols and polyphenols contained in olives. However, refined olive oil is a blend of slightly defective or low-quality olives which undergo thermal and chemical processes, in which most of these bioactive components are lost. Thus, in common olive oil that is sold as a mixture of refined olive oil (>80%) and virgin olive oil, the polyphenol content is much lower or missing.

In vitro findings support that the potential beneficial effect of virgin olive oil is mainly elicited by its minor components. Secoiridoid derivatives (oleuropein, oleocanthal), alcohols and phenols (tyrosol, hydroxytyrosol), flavonoids, and lignans are abundant olive oil polyphenols not generally present in other oils and fats and with demonstrated antioxidant, anti-inflammatory and anticancer activity through mechanisms as apoptosis induction, reduced angiogenesis, and cell proliferation as well as metastasis prevention. However, population-level studies on the impact of different types of olive oil on cancer are still very scarce.

A small dietary change easy to achieve and maintain

For the time being, we cannot modify our genes (which predispose us, but do not determine us) but we can change lifestyles that we know can help us prevent the development of the most diagnosed cancer in women worldwide. While we may believe that tiring lifestyle changes are the only way to achieve results, we are proposing a small dietary change easy to achieve and maintain to prevent breast cancer. Even if that means a small increase in food spending, this study highlights the health benefit that virgin olive oil being the culinary oil of choice can bring to women. Therefore, virgin olive oil should go beyond the Mediterranean regions and continue to grow in popularity worldwide.

Preparing a simple Mediterranean breakfast, consisting of whole grain toast with extra virgin olive oil. /Source: CAROLINA DONAT

Carolina Donat-Vargas is a postdoctoral researcher in chronic diseases at the Barcelona Institute for Global Health (ISGlobal) and at Karolinska Institutet in Stockholm, and a teaching collaborator at the Department of Preventive Medicine and Microbiology at the Autonomous University of Madrid. Marina Pollán is a member of GEICAM, director of the National Epidemiology Center (CNE) at the Carlos III Institute of Health and director of the CIBER for Epidemiology and Public Health (CIBERESP).

Carolina Donat-Vargas

Dr, Karolinska Institutet