Soy infant formula contains much more manganese than cow's milk or human breast milk—a finding that is raising concerns because of the potential of manganese to alter brain function. A new study adds to these concerns, showing that soy formulas may alter social behavior.
Mari Golub and colleagues fed cow's milk formula, soy formula with typical manganese levels, or soy formula with added manganese to rhesus monkeys, beginning at birth and continuing until the monkeys were four months old. The researchers report that both monkeys receiving the typical soy formula and those drinking the extra-manganese formula engaged in less play behavior and more "clinging" behavior when evaluated in pair interactions. The soy and extra-manganese groups also had shorter wake cycles and shorter periods of daytime inactivity than monkeys fed cow's milk formula. In addition, monkeys given the soy formula could be identified by their impulsivity, and monkeys in the extra-manganese group showed evidence of alterations in dopamine function. The researchers say their findings suggest that "components of soy formula, including manganese, may influence brain development as reflected in behavioral measures."
Previous research has suggested a link between manganese and attention deficit hyperactivity disorder (see related article, Crime Times, 2002, Vol. 8, No. 4, Page 7) or violent behavior (see related article, Crime Times, 1997, Vol. 3, No. 4, Page 1).
"Neurobehavioral evaluation of rhesus monkey infants fed cow's milk formula, soy formula, or soy formula with added manganese," M. S. Golub, C. E. Hogrefe, S. L. Germann, T. T. Tran, J. L. Beard, F. M. Crinella, and B. Lonnerdal, Neurotoxicology and Teratology, June 11, 2005 (epub ahead of print publication). Address: Mari Golub, Department of Internal Medicine, CNPRN, Room 1925, University of California, One Shields Avenue, Davis, CA 95616.