` New Study Suggests Olive Oil May Reduce Breast Cancer Risk - Olive Oil Times
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New Study Suggests Olive Oil May Reduce Breast Cancer Risk

By Paolo DeAndreis
Jul. 8, 2025 18:49 UTC
Summary Summary

New research from Italy sug­gests a poten­tial link between increased olive oil con­sump­tion and a lower risk of devel­op­ing breast can­cer, par­tic­u­larly estro­gen-neg­a­tive and prog­es­terone-neg­a­tive tumors. The study com­bined data from over 11,000 Italian women with a review of pre­vi­ous research to explore the impact of olive oil on breast can­cer risk, although fur­ther inves­ti­ga­tion is needed to con­firm these find­ings and clar­ify the role of olive oil in pre­vent­ing breast can­cer.

New research con­ducted in Italy intro­duces data show­ing a poten­tial cor­re­la­tion between increased olive oil con­sump­tion and a reduced risk of devel­op­ing breast can­cer.

The study, pub­lished by the European Journal of Cancer, com­bines two research approaches. First, researchers ana­lyzed data from more than 11,000 Italian women enrolled in the long-run­ning Moli-sani study. Over a 13-year fol­low-up, they tracked dietary habits and breast can­cer inci­dence.

To strengthen their find­ings, the team added a sys­tem­atic review of prior research. They exam­ined 13 obser­va­tional stud­ies and one ran­dom­ized clin­i­cal trial to assess the con­sis­tency of the link between olive oil and breast can­cer risk.

What we observed is a very lin­ear asso­ci­a­tion: the more olive oil peo­ple con­sumed, the lower the (breast can­cer) risk. With each addi­tional table­spoon, set at ten grams, we saw a pro­por­tional risk reduc­tion.- Marialaura Bonaccio, researcher, Neuromed Mediterranean Neurologic Institute

By merg­ing orig­i­nal epi­demi­o­log­i­cal data with a com­pre­hen­sive lit­er­a­ture review, the researchers aimed to shed new light on the poten­tial role of olive oil in reduc­ing breast can­cer risk.

While the asso­ci­a­tion with over­all breast can­cer risk remained incon­clu­sive, the results sug­gested a pos­si­ble inverse rela­tion­ship between olive oil intake and the risk of devel­op­ing rel­a­tively rare estro­gen-neg­a­tive and prog­es­terone-neg­a­tive tumors, which lack estro­gen and prog­es­terone recep­tors.

Estrogen and prog­es­terone recep­tors are pro­teins found in or on some breast can­cer cells that bind to these hor­mones.

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“Risk fac­tors may vary depend­ing on the type of tumor, par­tic­u­larly based on the pres­ence or absence of estro­gen recep­tors,” Marialaura Bonaccio, a researcher at the Neuromed Mediterranean Neurologic Institute and co-author of the study, told Olive Oil Times.

“In estro­gen-pos­i­tive tumors, the effect of hor­mones is very strong and may there­fore over­shadow the influ­ence of diet,” she added. ​“In con­trast, in estro­gen-neg­a­tive tumors, diet and other non-hor­monal fac­tors may play a more sig­nif­i­cant and more eas­ily rec­og­niz­able role.” 

“Some com­po­nents of olive oil, such as hydrox­y­ty­rosol and oleu­ropein, appear to inter­act specif­i­cally with mech­a­nisms related to estro­gen recep­tors,” Bonaccio added.

This could help explain why olive oil con­sump­tion may have dif­fer­ent effects depend­ing on the type of breast can­cer, specif­i­cally whether these recep­tors are present or not.

“We can­not speak of a pre­ven­tion effect [due to olive oil intake], as we do not have solid, incon­tro­vert­ible data,” Bonaccio said. ​“On top of that, we’re talk­ing about results from obser­va­tional stud­ies, a type of research that comes with well-known lim­i­ta­tions.”

In obser­va­tional stud­ies, researchers track what peo­ple eat and mon­i­tor health out­comes over time.

These stud­ies have sig­nif­i­cant lim­i­ta­tions, such as con­found­ing: peo­ple who eat health­ier often lead gen­er­ally health­ier lives, mak­ing it dif­fi­cult to iso­late the effect of diet alone.

Recall bias is another con­cern, as par­tic­i­pants may mis­re­port their food intake. Reverse cau­sa­tion is also pos­si­ble; for exam­ple, indi­vid­u­als might change their diet because they are already ill.

Since obser­va­tional stud­ies can only show asso­ci­a­tions, not cause-and-effect rela­tion­ships, they must be inter­preted with cau­tion and a thor­ough under­stand­ing of their con­text.

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To address these con­cerns, the researchers adjusted for var­i­ous fac­tors.

“As shown in the paper, those who con­sume more olive oil also tend to fol­low the Mediterranean diet more closely. We accounted for that in our mod­els to help iso­late the effect of olive oil per se,” Bonaccio said.

The researchers could not dis­tin­guish between dif­fer­ent grades of olive oil, such as extra vir­gin, because the Moli-sani cohort data does not make that dis­tinc­tion.

“That’s why our paper refers gener­i­cally to ​‘olive oil’, even though we know from other research that effects can dif­fer between extra vir­gin and other types,” Bonaccio noted.

Given that the Moli-sani study was con­ducted in a south­ern Italian region with a strong tra­di­tion of adher­ing to the Mediterranean diet and high-qual­ity olive oil pro­duc­tion, it is likely that the results pri­mar­ily reflect the impact of extra-vir­gin olive oil.

“We can rea­son­ably believe that, as it’s a rooted cul­tural ele­ment, but we don’t have the data,” Bonaccio cau­tioned.

The cohort ques­tion­naire asked par­tic­i­pants whether they used olive oil and how fre­quently.

One area the researchers could explore was the quan­tity of olive oil intake asso­ci­ated with poten­tial health impacts.

“What we observed is a very lin­ear asso­ci­a­tion: the more olive oil peo­ple con­sumed, the lower the risk. With each addi­tional table­spoon, set at ten grams, we saw a pro­por­tional risk reduc­tion,” Bonaccio said.

Specifically, the data sug­gest that con­sum­ing more than three table­spoons per day is asso­ci­ated with a 30 per­cent lower risk of over­all breast can­cer.

However, this result is not con­sid­ered sta­tis­ti­cally sig­nif­i­cant. The con­fi­dence inter­val for the risk esti­mate included 1.0, mean­ing the observed reduc­tion could be due to chance. This lim­its the strength of the find­ing in sci­en­tific terms.

Nonetheless, the trend con­tributes to a grow­ing body of evi­dence sug­gest­ing a poten­tial pro­tec­tive role of olive oil, par­tic­u­larly against more chal­leng­ing-to-treat can­cers.

“There seems to be a kind of thresh­old at three table­spoons. When we model it con­tin­u­ously, the rela­tion­ship stays lin­ear: more oil, lower risk,” Bonaccio said.

“Calories should be con­sid­ered; one table­spoon of olive oil con­tains about 100 calo­ries, but not all calo­ries are equal. One hun­dred calo­ries from olive oil are not com­pa­ra­ble to 100 calo­ries from sugar-loaded sodas,” she added.

Bonaccio also pointed out that other stud­ies, such as Spain’s PREDIMED, sup­port these find­ings.

“In that study, four table­spoons were used as the thresh­old for high Mediterranean diet adher­ence, though their table­spoons are 14 grams each. So, in short: it’s prefer­able to use olive oil as the main dietary fat,” she said.

According to Bonaccio, the cur­rent research does not yet pro­vide robust, spe­cific con­clu­sions regard­ing the rela­tion­ship between breast can­cer and olive oil.

“Adding to that, estro­gen- and prog­es­terone-neg­a­tive tumors are rare, so the num­bers avail­able for analy­sis are lim­ited,” she said. ​“What we have are indi­ca­tions, data that point in a spe­cific direc­tion, but fur­ther inves­ti­ga­tion is needed.

Bonaccio explained that many breast can­cer stud­ies do not include infor­ma­tion on recep­tor sta­tus.

“So even the stud­ies we reviewed often only pro­vide data on over­all can­cer or menopausal sta­tus, which are more com­monly reported, but not always include recep­tor infor­ma­tion,” she added.

According to the researcher, the fol­low­ing steps should include refin­ing epi­demi­o­log­i­cal tools, such as improv­ing ques­tion­naires and data col­lec­tion meth­ods.

“In the Moli-sani study, we do have data on how peo­ple use olive oil, whether raw, for fry­ing, or for sautéing, to name a few. Including that kind of detail could enrich the analy­sis,” Bonaccio explained.

“There’s still a lot of work to do. That said, with all due cau­tion, it is inter­est­ing to high­light this asso­ci­a­tion between olive oil con­sump­tion and reduced breast can­cer risk, and hope­fully encour­age other researchers to ana­lyze their data so we can build on these find­ings,” she con­cluded.

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