Hold the trash! It's not time to discard all those bottles of fat free dressing you have stored on your refrigerator door just yet.
Yes, a study done at Purdue University did make quite a splash this week with its report you absorb more of the nutrients in your salad if your dressing contains fat, but it didn't tell the whole story. What we really got was another example of the kind of research that proves why you shouldn't change your diet based on a single study.
What the Salad Dressing Study Did Find
The researchers wanted to see what type of fat and how much of it produced the biggest change in blood levels of certain fat-soluble phytonutrients. Their study included 29 healthy subjects who had to eat 9 salads containing baby spinach leaves, chopped tomato, and shredded carrots, each with a different type and amount of dressing.
The dressings were made with 3 types of fat: canola oil for its monounsaturated fat, corn oil for its polyunsaturated fat, and butter for its saturated fat. The amount of dressing on each salad provided either 3 grams of fat, 6 grams, or 20 grams. This made a total of nine different salad samples.
After the subjects ate each salad, their blood was tested to measure the absorption of carotenoids. Carotenoids are compounds with names like lutein, lycopene, beta-carotene and zeaxanthin that are found in plants and have numerous health benefits. Because carotenoids are fat soluble, they are better absorbed when consumed and digested with fat.
As expected, higher levels of carotenoids were found in the subjects' blood after eating salads with the higher amounts of fat. This held true for all three types of fat. The best absorption of carotenoids for the least amount of fat was seen with the canola oil, or monounsaturated fat.
What the Study Did Not Find
The study did not tell us what would happen if you ate other foods containing some fat along with those salads or put some fat-containing foods on them. Good nutrition science says you can use a fat free dressing and still absorb the carotenoids in your salad as long as another source of fat is consumed around the same time.
I have been advising clients for decades that a salad is not a meal unless you add some protein and a greater variety of vegetables than were included in this study. I also know that anyone who tries to get away with eating a plain salad and fat free dressing for a meal will not last long. Fortunately (in this case), the snack you reach for shortly afterwards will probably be high in fat.
So if you like to toss your salads with olives, nuts, avocado or cheese; top them with egg, chicken, salmon, tuna, falafel, steak or bacon; or follow them with lasagna, beef bourguignon or chicken tikka masala, go ahead and use that fat free dressing. Your carotenoid levels will be fine.
How many different dressings to have in your house?