Healthy Bones
Soy foods and Osteoporosis
Osteoporosis is a disease characterized by fragile, porous bones that break easily. Ten million Americans have this disease and another 34 million are believed to have low bone mass, which puts them at risk for developing osteoporosis. Although osteoporosis is usually painless in the early stages, it can result in severe back pain and deformity and limit the ability to walk over time. In older people, broken bones can even be fatal.
Preventing Osteoporosis with a Lifetime of Healthy Habits
The best defense against osteoporosis begins in childhood with a well-balanced diet that helps build strong bones. The bones are almost completely formed by age 20, and are at their most dense in the 30’s. Bones are dynamic, however; they are constantly breaking down and reforming — a process called remodeling. This is why calcium is a key nutrient throughout life, even after the skeleton has stopped growing. At around age 35, bone breakdown speeds up and efforts to maintain good bone health become especially important.
Eighty percent of those with osteoporosis are women. It is estimated that half of all women over age 50 will have an osteoporosis-related fracture at some point. Reduced estrogen production can increase calcium loss from the bones, which places women at especially high risk during the years just following menopause. Other factors that raise risk in both men and women include sedentary lifestyle, cigarette smoking, excessive alcohol use, and inadequate vitamin D and calcium intake.
Good dietary and lifestyle habits among older people not only help to slow or stop bone loss, but can actually increase the density of bones even after some bone loss has occurred. While vitamin D and calcium are important for bone health, they aren’t the only critical nutrients. Adequate protein is also required to help the body absorb calcium and support skeletal health.(1) Additionally, potassium and other compounds found in whole plant foods may help reduce calcium loss from the bones.(3, 4) Vitamin K, which is found in leafy green vegetables including some types of lettuce, is also an important nutrient for healthy bones.(5) Finally, regular exercise is crucial, since a sedentary lifestyle has been shown to speed up bone loss.(6)
Soy and Bone Health
Recently, the scientific community has taken particular interest in the role of soy foods in supporting bone health. Some of this interest stems from the fact that the soybean is a unique dietary source of isoflavones. Also referred to as phytoestrogens, isoflavones are thought to inhibit postmenopausal bone loss.
Studies show that women in Asia who consume more soy tend to have stronger bones than women who consume less.(7) One study that specifically evaluated bone fracture rates found that among Chinese postmenopausal women, soy intake was associated with a one-third reduction in risk for breaking a bone.(8) Soy was particularly influential against bone loss among women between the ages of 50 and 60.
In addition to these observational studies, there have also been about 20 clinical trials comparing bone loss between women who consumed soy foods or soy isoflavone supplements and women who didn’t eat soy or who took a placebo.(7) While the results were not completely consistent, they are generally encouraging. For example, in one study, postmenopausal women who consumed an isoflavone supplement showed bone density improvement in the hip and spine, when compared to women who did not consume isoflavones.(9) In fact, the effects of isoflavones appeared comparable to conventional hormone therapy, which is known to reduce risk for fractures.(10) In a separate two-year study, postmenopausal women who consumed isoflavone-rich soymilk had much less bone loss than women consuming soy milk low in isoflavones.(11)
Silk Soymilk for Healthy Bones
The U.S. government is currently investing more than 10 million dollars in three large, multi-year studies on the effect of isoflavones on bone health in postmenopausal women. While no firm conclusions about isoflavones and bones can be drawn until the results of these trials are known, it still makes good sense to include soy foods in a healthy diet. In addition to their isoflavone content, many soy foods provide an excellent source of calcium and other nutrients such as vitamin D and protein that help keep bones strong. Silk Soymilk is a natural source of isoflavones and is fortified with vitamin D and highly bioavailable calcium,(12) providing as much readily-absorbable calcium as dairy milk. Silk is a convenient everyday choice for drinking, over cereal and in recipes.
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12. Zhao Y, Martin BR, Weaver CM. Calcium Bioavailability of Calcium Carbonate Fortified Soymilk Is Equivalent to Cow's Milk in Young Women. J Nutr. 2005;135(10):2379-82.