Topping off a salad with a tasty fat-free or low-fat dressing may be a good way to help you slim down, but new research suggests it could be counterproductive for your overall health.
Salad vegetables are known to be rich in vitamins and other nutrients that are important for health.
But scientists at Purdue University in the US say that the full benefits of these nutrients may not be realised unless the right kind of salad dressing is used.
Their latest research suggests that the type of dressing - in particular its fat content - may affect the amount of beneficial compounds called carotenoids that are absorbed by the body following a meal.
Lead study author Dr Mario Ferruzzi, whose findings are published in the journal Molecular Nutrition and Food Research, explained: "If you want to utilise 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."
The researchers recruited 29 people, all of whom were given salads with dressings containing 3g, 8g or 20g of fat.
Some of the participants were given salad dressing based on butter (saturated fat), while others received canola oil (monounsaturated fat) or corn oil (polyunsaturated fat).
Among people who ate salad dressing rich in polyunsaturated fat, the more fat the dressing contained, the larger the quantity of beneficial carotenoids they absorbed from the salad vegetables.
However, this kind of dose-dependent relationship was not seen for monounsaturated fat-rich dressings, such as canola or olive oil. People who ate 3g of fat from this type of dressing absorbed the same levels of carotenoids as those who ate 20g of fat.
This suggests that salad dressings based on canola or olive oil could be particularly beneficial for those who want a low-fat option without missing out on the vital nutrients found in fresh vegetables.