Soy protein improved the tibia bones in female rats with poor levels of physical fitness, regardless of ovarian hormone status, according to a recent study, and researchers said the findings could have dietary implications for menopausal women.
Researchers think they have found more evidence of a relationship between the impact of soy protein on bone health.
Scientists from the University of Missouri studied the effects of soy versus corn-based diets on rats selectively bred to have low fitness levels. At 27 weeks of age, the rats were divided between those with and without ovaries to mimic effects of menopause.
Prior research has found that these rats are good models for menopausal women, since decreased physical activity and weight gain are serious health concerns for this population.
After randomization, they compared the impact of the soy diet on bone strength and metabolic function to rats fed a corn-based, soy-free diet. Rats followed their special diets for 30 weeks and were euthanized between 55 and 57 weeks of age.
Soy protein improved the tibia bones in female low-fit rats, regardless of ovarian hormone status, according to the recent study published in Bone Reports. In addition, they found that the soy-based diet also improved metabolic function of the rats both with and without ovaries, simulating the possible effect of pre- and postmenopause.
Previous soy protein research as it relates to osteoporosis targeted the idea that a bioactive component of soy has health promoting effects. However, soy is a complex food with many bioactive components that might have additive, synergistic, or even antagonistic effects, and researchers wanted to study soy in comparison to a diet made up mostly of corn. The researchers said the results support the benefits of dietary soy protein, rather than the isolated, individual components, and that the benefit may be seen even in women who have not yet reached menopause.
"The findings suggest that all women might see improved bone strength by adding some soy-based whole foods, such as tofu and soy milk, to their diet," said Pamela Hinton, professor of nutrition and exercise physiology, in a statement. "We also believe that soy-based diets can improve metabolic function for postmenopausal women."
This study was funded by the National Center for Complementary and Integrated Health, the Office of Dietary Supplements, and the National Cancer Institute.
Hinton PS, Ortinau LC, Dirkes RK, et al. Soy protein improves tibial whole-bone and tissue-level biomechanical properties in ovariectomized and ovary-intact, low-fit female rats. (2018). Bone Rep. doi: 10.1016/j.bonr.2018.05.002