In recent years, scientists have figured out that the conventional way of thinking about dietary fats had it all wrong. It used to be that any type of fat was considered unhealthy, and eating anything high in fat would send you straight down the road to all types of diseases, from heart attacks to organ failure to diabetes. But modern science holds that all fats are not created equal—and not all fats are bad for you. There are even good fats.

The two types of good fats you hear so much about in advertisements are polyunsaturated fats and monounsaturated fats. Unsaturated fats in general help fight the diseases that people once though were caused by any type of fats in the diet. But unsaturated fats are now thought to be beneficial in reducing cholesterol levels. Research suggests that monounsaturated fats are better than polyunsaturated fats, which are less stable and can reduce levels of good cholesterol as well as bad cholesterol. Recent dietary advice has stressed including monounsaturated fats in your diet, especially those found in fish oil and vegetable oils. Olive oil has been touted as being especially healthy, such as in the popular Mediterranean diet, which features many eating regimens involving olives and olive oil.

Researchers have found that even just one high-saturated-fat meal can rapidly reduce the ability of good cholesterol to protect arteries from the assault of bad fats, so such a meal should include monounsaturated fats to counteract the effects. Many people might think the best way to balance out a high-saturated-fat meal would be by including a healthy dose of olive oil in the cooking. But a study published recently in the Journal of American College of Cardiology, and partially funded by the California Walnut Commission, reported that a handful of walnuts can help protect arteries against the shock of a high-saturated-fat meal.

The study involved 24 adults who were of normal weight and did not smoke. Half of the participants had normal cholesterol levels, and the other half had moderately high cholesterol levels but were not on any medication to lower cholesterol. The study group participants were all given two identical meals, one week apart—a salami and cheese sandwich on white bread and a serving of full-fat yogurt. For one of the meals, half of the volunteers were given eight shelled walnuts along with their meal, while the other half were given five teaspoons of olive oil. For the second meal, the healthy fat additions were switched—the people who had been given walnuts the first time were given olive oil, and vice versa.

Tests showed that both the walnuts and the olive oil reduced the sudden onset of oxidation and inflammation in the participants arteries after they ate the high-fat meal. But surprisingly, the arteries of the participants who ate the walnuts remained more flexible than those who had the olive oil, regardless of the starting cholesterol level of the participants. The researchers performing the study decided that one difference may have been caused by the fact that walnuts contain a plant-based omega-3 fatty acid called alpha-linolenic acid, which helps boost artery-clearing HDL cholesterol and reduce inflammation.

Many studies have shown that various types of nuts help to reduce LDL cholesterol levels, and the FDA has issued statements advising that nuts—particularly walnuts, almonds, pecans, pistachios, hazel nuts, and peanuts—are a heart-healthy addition to the diet. A Spanish study showed that adding walnuts to a Mediterranean-type diet helps improve the function of blood vessels, helping to prevent hardening of the arteries. Investigators in that study concluded that adding nuts to the diet—particularly walnuts—can improve overall cardiovascular health in addition to the improvement seen from simply lowering cholesterol alone.

Although there are many dietary considerations that can help lower cholesterol and improve cardiovascular health, there is one simple and tasty thing you can do. The next time you feel the need to reach for a bag of chips, reach instead for a handful of walnuts. Your heart will thank you.