June 20, 2012
Specific Salad Dressings Impact Nutrient Absorption
Connie K. Ho for redOrbit.com
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When shopping for salad dressing, the flavors can run the gamut. Thousand Island, Ranch, Sweet and Sour, and others — not to mention the dozen options of fat, non-fat, and low-fat. However, a new study helps consumers better understand what dressings can help them absorb the most nutrients. Researchers from Purdue University found that certain salad dressings can help consumers get the best nutrients and vitamins from their salad.
In the study, the researchers observed participants who were fed salads with saturated, monounsaturated, and polyunsaturated fat-based dressings. The investigators then measured the participants´ blood to better understand the absorption of fat-soluble cartenoids, which are compounds like lutein, lycopene, beta-carotene, and zeaxanthin. The cartenoids are also linked to a decrease in various chronic and degenerative disease like cancer, cardiovascular disease, and macular degeneration. Results from the study showed that monounsaturated fat-rich dressings needed the least amount of fat to obtain the most cartenoid absorption, while saturated fat and polyunsaturated fat dressings needed higher amounts of fat to have the same result.
"If you want to utilize more from your fruits and vegetables, you have to pair them correctly with fat-based dressings," explained lead author Mario Ferruzzi, a Purdue associate professor of food science, in a prepared statement. "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."
In the project, 29 people were given salads served with butter as saturated fat, canola oil as a monosaturated fat, and corn oil as a polyunsaturated fat. Each salad had three grams, eight grams, or 20 grams of fat from the dressing. The dressing that was the most dependent on dosage was the soybean oil, which was rich in polyunsaturated fat. The saturated fat butter was also dependent on dosage, but not as much as the soybean oil. The researchers found that the more fat on the salad, the more cartenoids the participants absorbed.
As well, monosaturated fat-rich dressings, like canola and olive oil-based dressings, showed cartenoid absorption at three grams of fat as it did at 20 grams of fat. Researchers believe that this showed that this lipid source would be a good option for those who wanted to consume lower fat options, but still wanted to have optimal absorption of cartenoids from vegetables. Furthermore, the findings were based off of a 2004 Iowa State University study that investigated whether cartenoids could better be absorbed by the intestines if aligned with a full-fat dressing instead of a low-fat or fat-free dressing.
"Even at the lower fat level, you can absorb a significant amount of cartenoids with monounsaturated fat-rich canola oil," Ferruzzi said in the statement. "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."
In continuing the project, the researchers will investigate how meal patterning can influence nutrient absorption. Ferruzi hopes to better understand if people gain more nutrients by eating vegetables during one specific time or when consuming vegetables throughout the day. The current research findings will be published online in the journal Molecular Nutrition & Food Research.