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 may optimize the regulation of the body's natural defenses against reactive oxygen species (ROS) and free radicals.
The study focused on antioxidant response elements (AREs) on genes, which control the expression of internal defense systems that protect cells from free radical oxygen damage. To study the impact of plant-based antioxidant phytochemicals on AREs, the researchers 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).
"Our study shows at a cellular level how antioxidant phytochemicals might protect our cells and provide health benefits," said study co-author Nicholas Gillitt, Dole Food 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 the scientists 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.