Eating nuts two or more times per week protects a person’s cardiovascular system. The practice can also dramatically reduce the risk of fatal heart attack and stroke, according to nutrition researchers.

More than 5,000 adults aged 35 and older with no history of cardiovascular disease were  questioned about their dietary intake of nuts over a 12-year period, using a validated food frequency questionnaire. Nuts consumed included walnuts, almonds, pistachios, hazelnuts and seeds.

Eating nuts two or more times per week was associated with a 17% lower risk of cardiovascular mortality during the study period, compared to consuming nuts once every two weeks, investigators found. The association remained strong after adjusting for other mortality risk factors.

“Nuts are a good source of unsaturated fat and contain little saturated fat,” said study author Noushin Mohammadifard, Ph.D., Isfahan Cardiovascular Research Institute, Iran. “They also have protein, minerals, vitamins, fibre, phytosterols, and polyphenols, which benefit heart health.”

Raw, fresh nuts may provide the greatest benefits, Mohammadifard said. “[U]nsaturated fats can become oxidized in stale nuts, making them harmful. You can tell if nuts are rancid by their paint-like smell and bitter or sour taste.”

The study was presented on Friday at a summit of the world’s leading cardiologists in Paris.