Low-Fat or No-Fat Dressings Aren’t the Healthiest Option for Salads

Research shows the amount of dressing determines how many nutrients we absorb from a salad.

New research says that monounsaturated fat dressings, such as olive oil, are a smart salad dressing choice. The higher fat content in salad dressing, the more likely the body will absorb vital nutrients from the salad’s vegetables. Photograph courtesy of Flickr user USDAgov.

You’ve heard plenty about how salad dressings can load your healthy meal with unnecessary calories. But it turns out switching to fat-free ranch might not be the best choice, after all.

New research coming out of Purdue University suggests it’s not the type of salad dressing we choose to consume that keeps our salad nutritious—it’s the amount of dressing and how much fat it contains.

It’s common for people to believe low-fat or no-fat dressings keep
calories down and salad healthy. And while they do reduce calories, lead
researcher Mario Ferruzzi says these types of dressings actually limit
the amount of important nutrients we absorb from the vegetables.

Why? Common vegetables that appear in salads, including tomatoes, carrots, and spinach, are rich in carotenoids, pigments that protect cells from free radicals and boost our immune system. However, in order for our bodies to absorb these vital nutrients, we need fat to help extract them from the foods we digest, Ferruzzi explains.

For the study, researchers fed 29 subjects salads with three different types of fat: butter (saturated), canola oil (monounsaturated), and corn oil (polyunsaturated). Each salad contained either 3, 8, or 20 grams of fat from dressing.

After consumption, the researchers tested the subjects’ blood for absorption of carotenoids.

Researchers found that the more fat there was in the salad, the more carotenoids the subjects absorbed. The corn oil dressing salad was most dependent on dosage. The more grams of fat the salad contained with this dressing, the higher the amount of carotenoids researchers found in the subjects’ blood tests afterward. The butter dressing led to similar results. Therefore, researchers concluded that when consuming these types of dressings, the more fat, the better.

On the other hand, Ferruzzi noted that subjects who ate the canola oil dressing absorbed the same amount of carotenoids from the salad that contained 3 grams of fat as the one that contained 20 grams, suggesting that monounsaturated fat-rich dressings such as canola or olive oil are a good choice for those who still want low-fat options, since they can pour on less dressing and receive the same benefits.

The new findings match up with a 2004 study that found carotenoids were more likely to be absorbed when paired with full-fat dressing, researchers noted.

“You need to make sure you have some fat in your salad dressing,” Ferruzzi advised in a statement. “Some fat is healthy. With heart-healthy canola oil, you’ll get the same, if not slightly better, absorption rates depending on individual carotenoids.”

The full study was published in the Molecular Nutrition & Food Research journal.