It’s nuts to think that heart-healthy walnuts make old people fat, according to a new study.

Spanish researchers found that chowing down on walnuts doesn’t pose a problem for elderly people’s waistlines — and determined that a serving a day can actually crack other health issues.

“Given walnuts are a high-energy food, a prevailing concern has been that their long-term consumption might be associated with weight gain,” said Dr. Emilio Ros, one of the doctors who worked on the study from the Hospital Clinic of Barcelona.

But after monitoring 707 healthy older adults for a year, they found that those who regularly ate the crunchy snack didn’t pack on any more pounds than those on a nut-free diet.

And the people who did have a daily dose of walnuts actually lowered their LDL cholesterol.

“The well-known cholesterol-lowering effect of walnut diets works equally well in the elderly and is maintained in the long term,” Ros said. “It’s encouraging to see that eating walnuts may benefit this particular population.”

The Walnuts and Healthy Aging study is part of a two-year clinical trial out of the Hospital Clinic of Barcelona and Loma Linda University. The study was presented at the Experimental Biology conference in San Diego, which runs April 2-6.