Soy protein isolate and isoflavones modulate serum immunoglobulin levels in rats.

Xiao, C.; Wood, C.; L'Abbé, M. R.; Gilani, S.; Cooke, G.; Curran, I.

The antigenicity of soy protein and soy-derived isoflavones (ISF) as well as their effect on the development of immunologic mechanisms in soy formula-fed infants has not been well understood. The purpose of this study was to use rats as a model to examine the effect of alcohol-washed soy protein isolate (SPI) and supplemental ISF from Novasoy (a concentrate) on serum immunoglobulin (Ig) contents. Pubertal Sprague-Dawley rats were fed diets containing either 20% casein or 20% SPI ± ISF (250 mg/kg diet). At 120 days of age, the males and females from the same dietary group were mated to produce F1 pups. The F1 pups were fed the same diets as their parents, and killed at days 28, 70, 120, and 240. Serum IgA, IgE, IgG, and IgM levels in females were measured using ELISA. The rats fed the diet containing SPI alone had significantly higher IgA and IgM contents at day 28 and lower IgG level at day 240 than those fed the casein-based diet (p<0.05). Addition of ISF to the SPI-based diet further enhanced the serum IgA and IgM in day 28 rats (p<0.01), and markedly elevated IgG content in day 28, 70 and 120 rats compared with casein and SPI alone. However, neither SPI nor ISF had any effect on IgE, one of the allergy mediators. Overall, these results demonstrate that ISF is more antigenic than soy protein in young female rats, but both are not allergenic.

SOY proteins; ISOFLAVONES; IMMUNOGLOBULINS; SERUM; LABORATORY rats; ALLERGENS

Asia Pacific Journal of Clinical Nutrition, 2004, Vol 13, pS111

0964-7058

Academic Journal