Doctors have long been encouraging Americans to add more fruits and vegetables to their daily diets. Now, UC Davis researchers have discovered one way in which flavonoid-rich apples inhibit the kinds of cellular activity that leads to the development of chronic diseases, including heart disease and age-related cancers.
“We've known for a long time that it's the flavonoids in fruits that are protecting the body. We just haven't known exactly how. Now, at least in the case of apples, we have a good idea about what's going on,” said Eric Gershwin, professor of allergy, rheumatology and immunology at the UC Davis School of Medicine.
Gershwin and his colleagues found that apple extract was able to protect cells from damage and death by interfering with communication between cells.
The current findings appear in the latest issue of Experimental Biology and Medicine.
Earlier studies have shown that flavonoids-which are found in chocolate and green tea, as well as other fruits and vegetables-behave as anti-oxidants, taking up free oxygen radicals that can damage precious DNA. The UC Davis study takes that research further by looking beyond the antioxidant effects of apple flavonoids.
In the current study, Gershwin and his colleagues exposed human endothelial cells to an extract of an apple mash made from different apple varieties. The researchers then challenged these cells by exposing them to tumor necrosis factor (TNF), a compound that usually triggers cell death and promotes inflammation via a mechanism called the “nuclear factor (NF) kappa B pathway.” This pathway involves chemical signaling between cells. The apple extract was able to protect the cells from the normal lethal effects of TNF.
“Our study showed that the flavonoids in apples and apple juice can inhibit signals in this pathway that would otherwise damage or kill cells in the body,” Gershwin explained.
The method by which apple extract protects cells is different than that reported for other flavonoid-rich foods. Grape seed extracts, for example, do not affect the NF kappa B pathway, the authors wrote. In addition, they said, other studies indicate that it is not just the flavonoids in the apple extract that are important in protecting cells from genetic damage.
“The differences are likely due to the other biologically active ingredients found in the different fruits,” Gershwin said. “We need to know more about how fruits like apples are able to protect us from disease.”
This research was funded through an unrestricted grant from the U.S. Apple Association and the Apple Products Research and Education Council.
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