Many health-conscious people opt for low-fat or fat-free salad dressings, thinking they are making a smart and diet-friendly choice. But according to a new study from Purdue, diet dressings may actually prevent you from absorbing all the nutrients from those leafy greens.

For the study, a team of researchers gave volunteers three salads over the course of several days, each dressed with a different type of fat. One salad was topped with butter (saturated fat), one was topped with canola oil (monounsaturated fat), and the other was topped with corn oil (polyunsaturated fat). They also varied the fat content of each salad, at either three, eight, or twenty grams. After the volunteers consumed the salads, researchers took blood samples to determine carotenoid absorption.

Carotenoids are an important class of nutrients that have been associated with a reduction in cancer risk, eyesight protection, a lower risk of cardiovascular-related death, and even a healthy glow.

For saturated and polyunsaturated fats, the more a person consumed, the more carotenoids they absorbed. However, people who ate salads dressed with monounsaturated fats absorbed the same amount of carotenoids from the three, eight, and twenty gram of fat salads. Thus, the researchers concluded that monounsaturated fat-based dressings are a good option for people looking to reduce their overall fat intake. Canola oil, olive oil, and avocados are good sources of monounsaturated fat.

An added benefit – monounsaturated fats have also been shown to slow brain aging!

Mario Ferruzzi, the study’s lead author summarized: ”If you want to utilize more from your fruits and vegetables, you have to pair them correctly with fat-based dressings. If you have a salad with a fat-free dressing, there is a reduction in calories, but you lose some of the benefits of the vegetables.”

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