Low-Fat Salad Dressing Won't Protect You From Disease Canola oil proves to be the healthy exception By Neal Colgrass, Newser Staff Posted Jun 21, 2012 6:17 PM CDT 14 comments Comments (Shutterstock) (Newser) – That low-fat salad dressing? Might keep you slim, but it won't help you stave off serious illnesses like cancer and heart disease, reports the Daily Mail. Researchers from Iowa State University served up salads to participants with different dressings: corn oil (for polyunsaturated fat), canola oil (for monounsaturated fat) and butter (for saturated fat). Turned out the fattier dressings had robust long-range benefits. Tests showed that the more butter or corn oil people consumed, the more their blood contained fat-soluble carotenoids—compounds that help lower the risk of several degenerative and chronic diseases. Canola oil was an exception: It stimulated the same carotenoid absorption with just a fraction of the dose. Olive oil, also rich in monounsaturated fat, should give the same boost with a low dose.