Olive oil is a major component of the Mediterranean diet, and olive phenols have been shown to convey antioxidant, anti-inflammatory, anticancer, neuroprotective, and antidiabetic effects by modulating various molecular pathways, Andrea Paola Rojas Gil, PhD, of the University of Peloponnese, Tripoli, Greece, and colleagues wrote.
In most patients, CLL is incurable, but those at the early stages do not need immediate therapy and may benefit from an intervention to prevent disease progression, the authors wrote. Previous research suggested that dietary intervention exerts a salutary effect on early CLL, and in vitro studies suggested that oleocanthal, a component of extra virgin olive oil, induced anticancer activity.
In a study published in Frontiers in Oncology, the researchers enrolled adults with early stage CLL who had not undergone chemotherapy or other treatment. All patients adhered to a Mediterranean-style diet.
After a washout period of 9-12 months, the researchers randomized 22 patients to extra virgin olive oil high in oleocanthal and oleacein (high OC/OL-EVOO). Patients in the intervention group consumed 40 mL/day of high OC/OL-EVOO before meals. Their average age was 71 years; 10 were women and 12 were men.
The primary outcomes included changes in hematological, biochemical, and apoptotic markers. After 6 months, patients in the intervention group showed a statistically significant reduction in white blood cells and lymphocyte count, compared with measurements taken 3 months before the intervention. The WBC decrease was greatest among patients with the highest WBC levels at baseline.
As for biochemical markers, the researchers observed a significant decrease in glucose levels during the intervention, but no significant effects on metabolic indexes or renal function.
After 3 months and also after 6 months of the olive oil intervention, patients showed a significant increase in the apoptotic markers ccK18 and Apo1-Fas (P ≤ .05 for both), as well as an increase in the cell cycle negative regulator p21. The dietary intervention also was associated with significant decreases in expression of the antiapoptotic protein survivin and in cyclin D, a positive cell cycle regulator protein.
Further, patients who had a high ccK18 level at baseline showed a significantly greater increase in ccK18 after the intervention, compared with those with lower ccK18 at baseline (P = .001).
Notably, “a negative correlation of the WBC at the end of the dietary intervention with the fluctuation of the protein expression of the apoptotic marker ccK18 (final – initial) was observed,” the researchers wrote in their discussion.
The study findings were limited by several factors including the small sample size, short intervention time, and pilot design, the researchers said. Other limitations include the possible effect of other unmeasured properties of olive oil.
However, the results reflect previous studies showing the benefits of a Mediterranean-type diet, and they represent the first clinical trial to indicate possible beneficial effects from oleocanthal and oleacein on the progression of CLL. Therefore, the authors concluded, the study is worthy of a large, multicenter trial.