A new study by scientists at the NC Research Campus (NCRC) in Kannapolis, NC, claims to dispel popular theories that antioxidants “capture” free radicals and reactive oxygen species to reduce their damaging effects. Their findings instead claim that antioxidants actually build natural, cellular defenses.

Antioxidants are thought to “capture” or “scavenge” free radicals and reactive oxygen species (ROS) in the body to prevent their damaging cellular effects that contribute to aging and chronic disease. A new study by scientists at the UNC Chapel Hill Nutrition Research Institute (NRI) and the Dole Nutrition Institute (DNI) published in the Journal of Nutrition finds that phytochemicals in fruits and vegetables instead optimize the regulation of the body’s natural defenses against reactive oxygen species (ROS) and free radicals.

Both research organizations are located at the NC Research Campus (NCRC) in Kannapolis, NC. Their findings in the study “Extracts of fruits and vegetables activate the antioxidant response element in IMR-32 Cell” focused on antioxidant response elements (AREs) on genes, which control the expression of internal defense systems that protect cells from free radical oxygen damage. NRI Director Steven Zeisel, MD, PhD, emphasized that these findings do not reinforce long-held beliefs about how all antioxidant phytochemicals work.

“This study changes how we can recognize constituents of fruits and vegetables that improve our antioxidant defenses,” Dr. Zeisel said. “In the past, we looked for certain structures in phytochemicals that could trap free radicals, now we know that there are many ingredients in fruits and vegetables that work in a completely different way to activate our own internal defense systems.”

Determining Antioxidant Capacity
To study the impact of plant-based antioxidant phytochemicals on AREs, Dr. Zeisel’s team developed an assay using IMR-32 neuroblastoma cells. The DNI laboratory prepared 134 fruit and vegetable extracts using both the flesh and peel. When the extracts were exposed to the assay, 107 of them activated the AREs. Some of the most effective activators included avocado peel, carrot, red pear peel, pineapple, lemon flesh, green pear peel, red delicious apple peel, spinach and a variety of lettuces. The assay results more effectively determined antioxidant capacity than the commonly used measures of total phenolic compound content (TP) and oxygen radical absorption capacity (ORAC), researchers claimed.

“Our study shows at a cellular level how antioxidant phytochemicals might protect our cells and provide health benefits,” explained study co-author Nicholas Gillitt, PhD, Dole Food Company vice president of nutrition research and DNI director. “We found that more important than capturing and neutralizing oxidants and free radicals is the fact that the phytochemicals actually cause an upregulation in the expression of these AREs. This is new insight into why fruits and vegetables are healthy for us.”

Because Dr. Zeisel and Dr. Gillitt recognize that research in cell culture that examines one protection mechanism in the human body is far from definitive, they have two additional studies underway. The first is a human trial using whole fruits and vegetables blended into smoothies. AREs activation will be measured through analysis of blood draws taken before and after consuming the smoothies. The second study involves fractionating the extracts to determine the specific molecules that activate AREs. 

Impacts
For the NRI, an institute developing targeted nutrition, the finding is a critical step toward understanding how nutrition can be more effectively used to prevent chronic diseases. “Now we have the tools to recognize a whole new set of healthy ingredients in fruits and vegetables, many of which we had never considered before,” Dr. Zeisel commented.

For the DNI, the research and educational arm of Dole Food Company, the study is evidence that consuming fruits and vegetables has long-lasting effects. “Fruits and vegetables are healthy for us for a lot of reasons,” Dr. Gillitt added, “but we are showing why at a cellular level they are healthy and how important long-term exposure to phytochemicals is for our health now and thirty years from now.”