Why you need fat in your salad

While salads are packed full of nutrients and vitamins, lettuce lovers who choose low fat dressings may not be getting the full benefit of their healthy lunch choice, according to a new study in the US.

In a small trial, 29 people were given salads topped with various different dressings. They then had their blood tested for the absorption of fat-soluble carotenoids found in salad vegetables. These included lutein, lycopene, beta-carotene and zeaxanthin, which have all been linked to a reduced risk of cancer and cardiovascular diseases.

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The study investigated whether more of these compounds were absorbed by the body when the salad was eaten with an oil-based dressing compared to eating naked salad.

Three different oils were used - butter, a saturated fat, canola oil, a monounsaturated fat and corn oil, a polyunsaturated fat. They were also trialled in different amounts – three grams, eight grams or 20 grams of fat to discover how the absorption varied.

The researchers found that the polyunsaturated corn oil was very dependent on the quantity. The more corn oil used, the more nutrients were absorbed. This was also true to a lesser extent with the saturated fat butter.

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The monounsaturated canola based dressing proved to be as effective at three grams as it was at 20 grams, suggesting these types of oil, which also include olive, are ideal for those tried to cut down on fat without reducing their nutrient absorption.

"If you want to utilise more from your fruits and vegetables, you have to pair them correctly with fat-based dressings," said lead author Mario Ferruzzi, associate professor of food science at Purdue University, Indiana. "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."

"Even at the lower fat level, you can absorb a significant amount of carotenoids with monounsaturated fat-rich canola oil," Ferruzzi added. "Overall, pairing with fat matters. You can absorb significant amounts of carotenoids with saturated or polyunsaturated fats at low levels, but you would see more carotenoid absorption as you increase the amounts of those fats on a salad."

Time to ditch the vinaigrette?