As the Folsom-based California Walnut Commission marks the 20th anniversary of research that linked walnut consumption favorably with serum cholesterol levels, a Spanish study has again taken up the issue of heart health.

Researchers with the Hospital Clinic of Barcelona found that a Mediterranean diet including walnuts reduced cardiovascular disease risk by 30% and stroke risk by 49% over a reference low-fat diet, according to a news release.

The Spanish Predimed — short for Prevencion con Dieta Mediterranea — trial results were announced at Loma Linda University, source of the 1993 research on cholesterol published in the New England Journal of Medicine.

“(It) further demonstrates that a plant-based diet, infused with nutritious unrefined plant fats, can have long-lasting effects for heart health,” Joan Sabate, chair of the nutrition department at Loma Linda, said in the release. Sabate was principal investigator on the 1993 study.

The benefits derive in part from alpha-linolenic acid, a plant-based omega-3 fatty acid, according to Sabate.

The heart health studies are part of a broader research effort on walnut nutrition that’s addressed diabetes, weight management and other issues. There have been 91 studies since 1993, according to the commission. Eight projects have some funding from the American Institute for Cancer Research, totaling $488,000 in grants.

The Predimed study looked not only at risk factors but at clinical outcomes, David Jacobs, professor of epidemiology at the University of Minnesota, said in the release.

In 2004, the Food and Drug Administration affirmed a qualified health claim for walnuts. “Supportive but not conclusive research shows that eating 1.5 ounces of walnuts per day, as part of a low saturated fat and low cholesterol diet and not resulting in increased caloric intake may reduce the risk of coronary heart disease,” the agency said in a statement at the time.

In 2011, the American Heart Association certified walnuts as a heart-healthy food with its Heart-Check mark, an icon that consumers trust.