Could soy improve bone health in women?
The reduction in bone density and strength that is common in postmenopausal women is of huge concern.
As women age, osteoporosis, reduced activity levels, and weight gain act together to decrease bone health and negatively impact metabolism.
Osteoporosis and bone weakness increases the risk of fractures, which then lead to even more inactivity and weight gain, exacerbating the issue further.
As the population becomes — on average — older and heavier, bone health is an important area of medical science to study.
Recently, researchers from the University of Missouri in Columbia set out to test how alterations to a woman's diet might impact the resilience of her bones. In particular, they were interested in the effects of soy-based proteins.
Soy and bone strength
To investigate, the scientists utilized so-called low-capacity running rats, which have low fitness levels. Study co-author Victoria Vieira-Potter explains why they chose this model.
"Prior research has shown," she says, "that these rats are good models, as average American women are relatively inactive both before, and especially after, menopause."
The researchers surgically removed the ovaries of half of the rats to mimic menopause. They have now published their findings in the journal Bone Reports.
The scientists fed half of the rats a soy-based diet and the remaining animals a corn-based diet. Both diets contained the same amount of calories. They weighed the rats every week for the duration of the 30-week trial.
Then, the team took blood samples, tested bone strength, and assessed body composition using EchoMRI, an imaging technique that can accurately measure levels of body fat and water mass in live animals.
From the blood, they assessed markers for bone formation and bone resorption, a process wherein bones are broken down and minerals released into the blood. Markers of resorption and formation are collectively known as bone turnover markers.
The scientists inspected the microscopic structure of the animals' bones, and they also tested them mechanically to breaking point.
Marked improvements in bone strength
The analysis showed that, although turnover markers were not significantly altered, the leg bones of soy-fed rats were stronger than the bones of the rats that were fed a corn-based diet.
"Bottom line, this study showed that women might improve bone strength by adding some soy-based whole foods to their diet."
Lead study author Prof. Pamela Hinton
Prof. Hinton continues, "Our findings suggest that women don't even need to eat as much soy as is found in typical Asian diets, but adding some tofu or other soy, for example, foods found in vegetarian diets, could help strengthen bones."
The study also showed that the soy-based improvement in bone strength occurred in rats with and without ovaries; the authors write that, in both sets of rats, soy "significantly improved whole-bone strength and stiffness." In other words, even "postmenopausal" rats' bones benefited from the change in diet.
As Prof. Hinton concludes, "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. We also believe that soy-based diets can improve metabolic function for postmenopausal women."
The results are interesting and merit further investigation. The next step will be to understand the molecular mechanisms that underly the benefits of increased soy intake.
Once the team understands the process in more detail, it might be possible to harness the reactions involved and find ways to yield even greater benefits to bone strength.