— Benefits observed in non-Mediterranean population

by Nicole Lou, Staff Writer, MedPage Today March 5, 2020

Greater olive oil consumption was tied to lower cardiovascular disease (CVD) risk, but substituting plant-based oils for animal fats in general could also be helpful for most people, a study showed.

Comparing those who ate the most vs the least olive oil (people who ate at least 1/2 tablespoon of olive oil per day vs those who consumed olive oil less than once per month), Marta Guasch-Ferré, PhD, of Harvard T.H. Chan School of Public Health in Boston, and colleagues found that the former group had the following improvements in outcomes over 24 years of follow-up:

• Lower risk of CVD (fatal and non-fatal strokes and myocardial infarctions): HR 0.86 (95% CI 0.79-0.94)

• Lower risk of coronary heart disease (CHD): HR 0.82 (95% CI 0.73-0.91)

• No significant reduction in total or ischemic stroke risk

“Results were consistent across all subgroups, including participants with and without Southern European ancestries,” the researchers wrote in the study, which was presented at the American Heart Association’s EPI Lifestyle meeting in Phoenix and simultaneously published in the Journal of the American College of Cardiology.

The data, adjusted for major diet and lifestyle factors, were notable for coming from a relatively healthy, non-Mediterranean population, the researchers said.

Replacing 5 g of margarine, butter, mayonnaise, or dairy fat per day with olive oil was associated with a 5-7% lower risk of CVD and CHD, the authors noted. However, olive oil did not reduce events when eaten in lieu of other plant oils.

“Therefore, consumption of other plant oils could also be a healthy alternative when compared to animal fat, especially because they tend to be more affordable in the U.S. compared to olive oil. However, further research is needed to confirm the effects of plant oils on health outcomes,” the study authors said.

Notably, PREDIMED, a landmark trial that had suggested benefit to the Mediterranean diet known for its olive oil component, was retracted in 2018. Guasch-Ferré was one of the investigators who worked on that trial.

For now, she and her colleagues said, the data support existing recommendations to replace saturated fat and animal fat with unsaturated plant oils for the prevention of CVD.

The present study included 61,181 women from the Nurses’ Health Study and 31,797 men from the Health Professionals Follow-up Study. These were individuals who were free of cancer, heart disease, and stroke at baseline in 1990, the year that olive oil consumption was first included in the food frequency questionnaires of those studies.

Food questionnaires were completed at baseline and every 4 years thereafter.

Average daily consumption of olive oil increased from 1.30 g in 1990 to 4.2 g in 2010 (one tablespoon was considered to be equivalent to 13.5 g of olive oil).

People who ate more olive oil tended to consume more calories in general and to report higher intakes of nuts, fruits and vegetables, and other plant oils.

From the subset of patients who gave plasma samples for the study, it appeared that higher olive oil intake was associated with lower levels of circulating inflammatory biomarkers interleukin-6, soluble intercellular adhesion molecule-1, and tumor necrosis factor α-R2; and higher high-density lipoprotein cholesterol but no change in low-density lipoprotein cholesterol.

“Of note, during the earlier part of the follow-up, many margarines contained substantial amounts of trans fatty acids and the results may not apply to current margarines,” Guasch-Ferré’s group acknowledged.

The observational nature of the study also precluded any causal findings and left room for residual confounding, the investigators said. Additionally, the cohort of predominantly non-Hispanic white nurses and health professionals may have limited the generalizability of the data. Having study participants self-report their olive oil intake meant that measurement errors were another possible limitation, the team added.