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Fat helps your body absorb the nutrients in vegetables...

What could be more healthful than a big green salad topped with nonfat dressing? The answer is... that same salad but with full-fat dressing!

Eating fresh vegetables with a little fat, such as oil-based salad dressings or cheese, helps the body absorb valuable nutrients found in vegetables, such as lycopene and beta-carotene.

In contrast, eating a salad without any fat in it may deprive your body of these healthy nutrients, known as phytochemicals.

In the study, which appears in the American Journal of Clinical Nutrition, researchers compared nutrient absorption after eating salads with varying levels of fat [1].

Seven healthy men and women ate salads of spinach, romaine lettuce, cherry tomatoes, and carrots topped with Italian dressings containing 0, 6 (0.2 ounces), or 28 grams (almost 1 ounce) of canola oil on different occasions during a 12-week period. Hourly blood samples were taken for 11 hours after the meal and tested for nutrient absorption.

The study shows that only negligible amounts of alpha- and beta-carotene and lycopene were detected in the blood after eating a salad with fat-free dressing. More of these substances were detected in the blood after eating salads with reduced-fat dressing or full-fat dressings.

Similar findings have been presented in the March 2005 issue of the journal Nutrition [2]. The study shows that avocados act as a nutrient "booster," allowing the body to significantly absorb more nutrients like alpha-carotene, beta-carotene and lycopene found in fruits and vegetables.

A group of men and women consumed salads and salsa with and without fresh avocado. More than four times as much lycopene and twice as much beta-carotene was absorbed by subjects who ate avocado with salsa compared to those who ate only salsa.

Similar results were found with the salad. More than five times as much lutein, fifteen times as much beta-carotene, and seven times as much alpha-carotene was absorbed by subjects who ate avocado with salad compared to those who ate only salad.

"Many fruits and vegetables are rich in beneficial carotenoids, but most fruits and vegetables are virtually fat free, which may limit the body's ability to absorb some of these nutrients," says Dr. Steven Schwartz from Ohio State University, who is a co-author of both studies.

"Our latest research shows that the natural fat content in avocados increases carotenoid absorption, which offers nutritional advantages over other sources of fat like salad dressings."

Dr. David Heber, Professor of Medicine at the UCLA School of Medicine, concurs with Dr. Schwartz. "While it is well known that fats help in the absorption of colorful compounds that are good for you such as lycopene from tomatoes and lutein from dark greens, the good fats from olives and avocados are better for you than many processed salad dressings made with hydrogenated vegetable oils."

"We're certainly not advocating a high-fat diet, or one filled with full-fat salad dressing," says researcher Wendy White, associate professor of food science and nutrition at Iowa State University.

"But what we found compelling was that some of our more popular healthful snacks, like baby carrots, really need to be eaten with a source of fat for us to absorb the beta carotene," says White. "If you'd like to stick with fat-free dressing, the addition of small amounts of avocado or cheese in a salad may help along the absorption."

References
1. Brown, M.J., Ferruzzi, M.G., Nguyen, M.L., Cooper, D.A., Eldridge, A.L., Schwartz, S.J., & White, W.S. (2004). Carotenoid bioavailability is higher from salads ingested with full-fat than with fat-reduced salad dressings as measured with electrochemical detection. American Journal of Clinical Nutrition, 80, 396-403
2. Unlu, N.Z., Bohn, T., Clinton, S.K., & Schwartz, S.J. (2005). Carotenoid absorption from salad and salsa by humans is enhanced by the addition of avocado or avocado oil. Journal of Nutrition, 135, 431-436


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