May 12, 2004 -- Tangerine peels have more potent health benefits than the juice and could have powerful cholesterol-lowering potential, a new study shows.
Previous studies have shown numerous health benefits from drinking citrus juices like orange and grapefruit juice -- including their anti-inflammatory and anticancer properties. Studies have also hinted at a cholesterol-lowering capability in juices.
But disease-fighting flavonoids -- antioxidants found in foods -- are packed in higher concentrations in citrus peels than in juice, writes lead researcher Elzbieta M. Kurowska, PhD, with KGK Synergize Inc., in London, Ontario. Her study appears in the current issue of the Journal of Agricultural and Food Chemistry.
A few researchers, including Kurowska, have examined flavonoids found in citrus peels. The compounds, known to researchers as polymethoxylated flavonoids, are similar to plant pigment antioxidants found in citrus fruits.
The most common of these super-flavonoids -- tangeretin and nobiletin -- exist in orange and tangerine peels, and in smaller amounts in the fruits' juices, explains Kurowska.
Previous animal studies have shown that similar flavonoids -- herperidin from oranges and naringin from grapefruit -- may have cholesterol-lowering ability. However, those flavonoids are not as potent as the super-flavonoids, she says.
Hers is the first study looking at the super-flavonoids' cholesterol-lowering potential, she writes.
"Our study has shown that [super-flavonoids] have the most potent cholesterol-lowering effect of any other citrus flavonoid," says Kurowska in a news release. "We believe that [super-flavonoids] have the potential to rival or even beat the cholesterol-lowering effect of some prescription drugs, without the risk of side effects."
Taking super-flavonoid supplements could be an easier way to lower cholesterol than drinking 20 or more cups of juice daily -- the equivalent of the peel's amount of flavonoids, she says.
Save the Peel
Kurowska's study focuses on the super-flavonoids tangeretin and nobiletin found in tangerines. In the study, she fed hamsters a cholesterol-boosting diet -- the hamsters' LDL (bad) cholesterol levels jumped about 40%. Then, she fed hamsters with either a tangeretin supplement, a tangeretin/nobiletin mixture, or a commercially available tangerine flavonoid supplement.
Eureka! The hamsters benefited from all the tangeretin and nobiletin flavonoids. Total cholesterol and LDL cholesterol were significantly reduced -- without altering the HDL "good" cholesterol level, writes Kurowska.
Even much smaller amounts of the two flavonoids helped cholesterol significantly, she writes.
In fact, the peel flavonoids had three times higher cholesterol-lowering power than the juice, she writes. Her earlier studies have shown similar potential for peels.
These peel-derived compounds are more concentrated and easily absorbed and metabolized, she writes.
A long-term study involving humans is in progress to test the supplements' ability to lower cholesterol, Kurowska reports.
SOURCE: Kurowska, E. Journal of Agricultural and Food Chemistry, May 12, 2004.