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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