Researchers in the Linus Pauling Institute at Oregon State University discovered from an analysis of 446 compounds that just two stood out from the crowd - the resveratrol found in red grapes and a compound called pterostilbene from blueberries, for their ability to boost the innate immune system in humans.
Both of these compounds, which are called stilbenoids, worked in synergy with vitamin D and had a significant impact in raising the expression of the human cathelicidin antimicrobial peptide, or CAMP gene, that is involved in immune function.
The findings were made in laboratory cell cultures and do not prove that similar results would occur as a result of dietary intake, the scientists said, but do add more interest to the potential of some foods to improve the immune response.
"Out of a study of hundreds of compounds, just these two popped right out," said Adrian Gombart, an LPI principal investigator and associate professor in the OSU College of Science. "Their synergy with vitamin D to increase CAMP gene expression was significant and intriguing. It's a pretty interesting interaction."
Resveratrol has been the subject of dozens of studies for a range of possible benefits, from improving cardiovascular health to fighting cancer and reducing inflammation. This research is the first to show a clear synergy with vitamin D that increased CAMP expression by several times, scientists said.
The CAMP gene itself is also the subject of much study, as it has been shown to play a key role in the "innate" immune system, or the body's first line of defense and ability to combat bacterial infection. The innate immune response is especially important as many antibiotics increasingly lose their effectiveness.
A strong link has been established between adequate vitamin D levels and the function of the CAMP gene, and the new research suggests that certain other compounds may play a role as well.