Health benefits of oranges go beyond vitamin C, research shows

• Oranges rich in vitamin C offer another important yet lesser-known nutritional bonus: citrus limonoids.
• In laboratory tests with animals and with human cells, citrus limonoids have been shown to help fight cancers of the mouth, skin, lung, breast, stomach and colon.
• Agricultural Research Service scientists in northern California, led by chemist Gary D. Manners, are uncovering new details about these compounds.
• Manners and coinvestigators have reported their findings in studies published during the past several years.
• They've demonstrated, for example, that each time we bite into a citrus slice or drink a glass of orange juice, our bodies can readily access a limonoid called limonin.
• The team was the first to show limonin's "bioavailability."
• The body derives limonin from a parent compound--limonin glucoside--that's present in citrus and citrus juices in about the same amount as vitamin C, according to Manners.
• He's with the agency's Western Regional Research Center in Albany, Calif.
• In other early work, Manners and colleagues found that limonin may lower cholesterol.
• The researchers showed that, when exposed to limonin, human liver cells in petri dishes produced less apo B, a compound associated with higher cholesterol levels.
• High cholesterol levels are linked to increased risk of heart disease and other health problems.
• Now, Manners and coinvestigators are taking a closer look at limonin's cholesterol-lowering effects.
• They're doing that in a first-of-its-kind study with healthy volunteers.
• Manners is collaborating with researchers at Albany and at the ARS Western Human Nutrition Research Center in Davis, Calif.
• ARS is the U.S. Department of Agriculture's chief scientific research agency.