Susan Zunino, a molecular biologist with the Agricultural Research Service’s (ARS) Western Human Nutrition Research Center (WHNRC) in Davis, California, studies phytochemicals—natural compounds found in fruits such as grapes and strawberries. Her recent work suggests that phytochemicals from grapes may have a positive effect on the immune system of obese individuals.
Hospital and clinic documentation of viral and bacterial infection has shown that obese people are at a much higher risk for developing infections after surgery, according to Zunino. About 35 percent of Americans are obese, which puts them at a higher risk of developing heart disease, diabetes, and bacterial and viral infections.
In the study, obese participants drank either a mixture of water and grape powder made from freeze-dried table grapes or a placebo twice a day for three weeks. The two groups switched to the opposite mixture for the next three weeks.
Blood samples were analyzed to measure the effects of grapes on blood lipids (fats), blood markers of inflammation and cells of the immune system during the study. Compared with the placebo group, the grape powder group had reduced plasma concentrations of low-density lipoprotein (LDL), known as “bad” cholesterol, which is associated with heart disease.
When scientists stimulated immune cells from blood with a bacterial component, they found an increase in the production of proteins—cytokines—that are instrumental in fighting off infections. In previous research, Zunino discovered that one of the same cytokine proteins was produced when obese individuals consumed strawberry powder.
However, obesity leads to more inflammation in the body, according to Zunino. Therefore, more studies are needed to find out if the increase in cytokine production, after grapes and strawberries are eaten, contributes to more inflammation or is beneficial in reducing infections.
ARS is USDA’s principal intramural scientific research agency.
Read more about this work in the March 2016 issue of AgResearch.