While salad may be a great way to mainline your five-a-day, you won't get much benefit without the right type and amount of salad dressing, a Purdue University study suggests.

Researchers measured the levels of carotenoids absorbed by individuals after they ate salads topped off with saturated, monounsaturated and polyunsaturated fat-based dressings.

low fat

Carotenoids, such as lutein, lycopene, beta-carotene and zeaxanthin compounds, have been associated with reduced risk of several chronic and degenerative diseases such as cancer, cardiovascular disease and macular degeneration.

The study, published in the journal Molecular Nutrition & Food Research, found that monounsaturated fat-rich dressings required the least amount of fat to get the most carotenoid absorption, while saturated fat and polyunsaturated fat dressings required higher amounts of fat to get the same benefit.

Scroll down to find out how 'fat replacements' are added to your food

"If you want to utilize more from your fruits and vegetables, you have to pair them correctly with fat-based dressings," said Mario Ferruzzi, the study's lead author and a Purdue associate professor of food science, in 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."

Fat substitutes in food have also been associated with health problems, such as metabolic syndrome and weight gain.

Another study by Purdue University last year found that synthetic fat substitutes used in low-calorie potato chips and other foods could backfire and contribute to weight gain and obesity

Rats on high-fat diet gained more weight after eating low-calorie potato chips made with fat substitutes, which challenges the conventional wisdom that foods made with fat substitutes help with weight loss.

For rats on the high-fat diet, the group that ate both types of potato chips consumed more food, gained more weight and developed more fatty tissue than the rats that ate only the high-calorie chips.

The fat rats also didn't lose the extra weight even after the potato chips were removed from their diet.

"Based on this data, a diet that is low in fat and calories might be a better strategy for weight loss than using fat substitutes," Swithers said.

Another study has also found an association between high diet cola consumption and large waist circumference, and additional research has also found a link to heart attack and stroke risk.

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  • Microparticulated Protein

    Made from whey protein, or milk and egg protein, this fat replacer is included dairy products, such as ice cream, butter, cheese, yogurt, mayonnaise-type products, and baked goods, soups and sauces.

  • Gums

    Virtually non-caloric, these hydrophilic colloids or hydrocolloids, known as gums, guar gum, gum arabic, locust bean gum, xanthan gum, carrageenan and pectin, provide thickening, sometimes gelling effect; can promote creamy texture. Used in reduced-calorie, fat-free salad dressings and to reduce fat content in other formulated foods, including desserts and processed meat.

  • Dextrins

    These calorie and fat replacers can replace all or some of the fat in a variety of products. They can be found in salad dressings, puddings, spreads, dairy-type products and frozen desserts.

  • Inulin

    Extracted from chicory root, this reduced-calorie fat and sugar replacer, fiber and bulking agent can be found in yogurt, cheese, frozen desserts, baked goods, icings, fillings, whipped cream, dairy products, fibre supplements and processed meats.

  • Oatrim

    Hydrolyzed oat flour is used as a fat replacer, bodying and texturizing ingredient. Reduced calorie (1-4 calories/gram) as used in baked goods, fillings and frostings, frozen desserts, dairy beverages, cheese, salad dressings, processed meats and confections

  • Polydextrose

    This water-solubly polymer is a fat replacer and bulking agent, used in a variety of products including baked goods, chewing gums, confections, salad dressings, frozen dairy desserts, gelatins and puddings.

  • Salatrim

    A five calorie-per-gram family of fats (made up of short and long-chain acid triglyceride molecules) that can be adapted for use in confections, baked goods, dairy and other applications.