Researchers at the University of Illinois at Urbana-Champaign (UIUC) found that the soy isoflavone genistin may reduce a baby's susceptibility to rotavirus infections by as much as 74 percent.
The study, published in September's Journal of Nutrition , exposed cells in culture to rotavirus in both the absence and presence of soy isoflavones.
According to the researchers, the results could flag up soy isoflavones as a potential alternative to expensive rotavirus vaccines that are inaccessible to poorer families.
"It's exciting to think that the isoflavones in soy formula could be a cost-effective nutritional approach to decreasing the incidence and severity of rotavirus infections, especially among children in developing countries who are most at risk," said Sharon Donovan, professor of Nutrition at UIUC.
During 2004 alone, the World Health Organization (WHO) estimates around 527,000 deaths in children worldwide were caused by the rotavirus infection.
These deaths represented approximately five percent of all child deaths globally.
"Rotavirus is the primary cause of diarrhea in infants, affecting virtually all children before age five," said Donovan.
"In the United States, it mainly leads to dehydration, doctor's visits, and parents missing work to care for sick children."
Soy isoflavones are the biologically active compounds in soy that are thought to have health benefits, such as relieving the symptoms of menopause, increasing bone density and reducing cholesterol.
Genistin is the major isoflavone in soy.
Soy as an ingredient has already gotten a large plug from a US Food & Drug Administration approved health claim linking it to heart disease risk reduction: "Diets low in saturated fat and cholesterol that include 25 grams of soy protein a day may reduce the risk of heart disease.
One serving of (name of food) provides ____ grams of soy protein."
As part of the UIUC study, performed by doctoral candidate Aline Andres, different forms of soy isoflavones were tested individually as well as together in the complete mixture that is used in infant formula.
"Genistin and the mixture significantly reduced rotavirus infectivity by 33 to 74 percent," said Donovan.
"But when genistin was taken out of the mixture, anti-rotavirus activity was lost, suggesting that it is the active component in reducing infectivity."
Throughout the course of the study, funded by the US Department of Agriculture and the Illinois Soybean Association, rotavirus inhibition began at the isoflavone concentrations used in soy formula, and then levelled off.
According to the researchers, this points to the existence of a level of ingestion at which soy isoflavones is effective, beyond which there is no additional benefit for preventing rotavirus.
"We then exposed the cells to different concentrations of rotavirus," said Donovan.
"If an infant had a severe infection or was exposed to a lot of rotavirus, we wondered if the isoflavones would still be as effective."
The researchers involved now plan to take their investigation one step closer to humans by conducted studies on neonatal piglets.
"We'll be interested to see if we have the same results when we work with young animals," said Donovan.
Source: Andres, Aline et al.
"Isoflavones at concentrations present in soy infant formula inhibit rotavirus infection in vitro ."
Journal of Nutrition .
2007 137: 2068-2073.