COLUMBUS, Ohio - Small fruit crops such as strawberries and black raspberries can effectively uptake selenium, increasing concentrations of the nutrient in its leaves and berries and providing potential health benefits for consumers.
Ohio State University researchers have found that by adding 500 parts per million of selenium as a foliar spray onto newly emerging plant leaves, selenium uptake in the leaves increased 162 percent and in berries increased 96 percent. By doubling the amount of selenium added to the plant, uptake in the leaves increased 446 percent and in berries increased 240 percent.
The purpose of the work is to determine the bioavailability of components such as selenium in plant products and how that availability can meet a consumer's nutritional needs.
"Ohio soils in general are low in selenium and have high concentrations of iron which can restrict selenium uptake in plants," said Dick Funt, an Ohio State small fruit specialist. "If we can find a way to add selenium to plants and increase uptake in the berries, then that might make for an improved consumer product."
Berries are known to contain a wide array of nutritional components and antioxidants that help in fighting off cancer and prevent some medical conditions, such as heart disease. Studies have shown that selenium, a mineral found in berries in varying amounts, produces antibodies, helps to maintain a healthy heart and liver, and may help prevent certain cancers such as prostate and lung cancers. Other studies have shown that selenium combined with vitamin E provides an added health benefit.
"Selenium is looked upon as necessary, not just for prostate cancer, but for other illnesses and diseases," said Funt.
Funt said one of the goals of the project is to find the right amount of selenium that the plants will uptake and hold in meeting daily nutritional recommendations. "Adding 500 ppm of selenium increased selenium concentrations in berries from .233 to 2.2 ppm per gram of freeze-dried berries. By adding 1,000 ppm of selenium, that number jumped to 5.5 ppm per gram," said Funt. "We want to know what that translates into when it comes to recommended dietary intake - if that's sufficient for what people need."
The recommended daily intake of selenium is 55 micrograms (mcg) for women and 70 mcg for men, although nutritionists argue that amount can be increased to at least 200 mcg for added health benefits. Selenium taken in large doses, however, can cause medical problems. Doses of 800 mcg per day can cause loss of hair, nails and teeth and gastrointestinal upset.
Ohio State researchers have just begun their fourth year of studies of nutrient uptake in plants and have found that selenium uptake in the plants varies among cultivars and among soil types in Ohio.
"Selenium uptake is more efficient before bloom and some cultivars uptake selenium more effectively than others," said Funt.
The researchers plan to extend the study to other berries, such as blueberries and red raspberries. "We are looking at the berry as a vehicle for possibly having a safer effect on nutrient consumption than what one would take through a vitamin," said Funt. "At least consumers would have the option of meeting their dietary allowances through either a chemical or an organic form."