Is soy beneficial for postmenopausal women?

Secret in the Sauce

Is soy beneficial for postmenopausal women?

It is according to a new study from China. But before you grab your keys and rush out to the store to stock up on soy foods, there’s one little soy secret you need to know.

Over there

First we’ll take a quick look at the Chinese study, conducted by joint team from the Shanghai Cancer Institute and Vanderbilt University School of Medicine in Nashville, TN.

Based on previous evidence that soy intake may increase bone mineral density in postmenopausal women, the Shanghai/Nashville team conducted a population-based study to examine the effect of soy consumption on bone fracture risk. More than 24,000 women over the age of 40 were recruited from the Shanghai Women’s Health Study. Soy food intake for each subject was evaluated at the outset of the study and during a follow up period that lasted more than four years. By the end of the study period, nearly 1,800 fractures had been reported.

The results:

  • A high intake of soy foods was significantly linked with a reduced risk of fracture
  • Risk was reduced nearly 30 percent among women who had the highest soy intake and had been menopausal for more than a decade
  • Risk was reduced by almost 50 percent among women in early menopause with the highest intake of soy
  • The results were all computed after taking into account potential mitigating factors such as osteoporosis risk, age, other nutrients in the diet and socioeconomic status. But one very important mitigating factor was not considered: where the women lived.

Meanwhile, stateside

Soy contains phytates that block absorption of proteins and minerals, such as calcium. So how could the Shanghai women who consumed the most soy foods have the lowest risk of fractures when they weren’t absorbing calcium adequately?

Answer: fermentation.

In the e-Alert “Adult Swim” HSI Panelist Allan Spreen, M.D., explained that the phytates in soy are deactivated when soy is fermented. When soy sauce, tempeh and miso are made by the traditional method (which calls for fermentation), the phytates are neutralized, allowing the proper absorption of nutrients.

Fermented soy foods are the norm in Asia, but not in the West. So in a typical cohort of 24,000 U.S. women (in, say, Akron, OH), those who had the greatest soy intake from U.S. produced soy sauce, tofu or soy milk, would almost certainly not enjoy any reduction in fracture risk. In fact, they might very well be at greater risk.

And to make matters worse, they might also have a higher risk of developing kidney stones. In an e-Alert I sent you in 2001, I told you about a study that identified a potential link between soy consumption and kidney stones. That research, published in the Journal of Agricultural and Food Chemistry, showed how soybeans, tofu, and commercially processed soy products contain an extremely high amount of oxalate, a compound that binds with calcium in the kidneys, increasing the risk of kidney stone development.

For a much broader overview of the health hazards of soy, Dr. Spreen recommends what he calls a “somewhat scary” article titled “The Ploy of Soy” by Sally Fallon and Mary G. Enig, Ph.D., published online at westonaprice.org. It’s important to note that the Weston A. Price Foundation is a pro-raw dairy group. Still, this article and others that appear in the “Soy Alert!” section of their web site clearly demonstrate that soy as we know it here in the U.S. is a far cry from health food.

Sources:
“Prospective Cohort Study of Soy Food Consumption and Risk of Bone Fracture Among Postmenopausal Women” Archives of Internal Medicine, Vol. 165, No. 16, 9/12/05, archinte.ama-assn.org
“Soyfoods Cut Risk of Fractures in Older Women” NutraIngredients-USA, 9/13/05, nutraingedients-usa.com