The October 1999 U.S. Food and Drug Administration announcement that eating 25 grams of soy protein per day lowers the risk of coronary heart disease may soon rank soy foods right up there with broccoli. In addition to containing beneficial phytoestrogens called isoflavones, soybeans are valued for their high protein content, which accounts for nearly 35% of their overall composition. Soy protein prompted the health claim because it lowers cholesterol and the risk of heart disease.

R.M. Bakhit and colleagues at the University of Illinois fed men with mildly high cholesterol a low-fat diet including a daily muffin containing 25 grams of protein and 20 grams of dietary fiber. The muffins were one of four combinations: soy protein and soybean fiber; soy protein and cellulose; casein, a milk protein, and soybean fiber; or casein and cellulose. After two weeks of eating a straight low-fat diet, the subjects tested each different protein/fiber muffin combination for four weeks at a time. At the end of every dietary treatment, low-density lipoprotein, very low-density lipoprotein, and high-density lipoprotein were measured.

Bakhit and his team found that the muffins containing casein did not have a significant effect on cholesterol. In contrast, the two muffins containing isolated soybean protein significantly lowered total cholesterol levels in subjects whose initial concentrations were high. The results clearly suggest that a daily intake of 25 grams of soy protein can help prevent heart disease by lowering total cholesterol. Similar results were also observed by K. K. Carroll and colleagues at the University of Western Ontario. Considering the volume of clinical data that supports the findings of these two studies, as well as the fact that the FDA now allows a heart health claim for soy protein, there is no question that incorporating the nutrient into a low-fat diet can have beneficial effects. Besides lowering their risk of certain cancers, we also can look to soy foods as a means of preventing osteoporosis.

Moreover, soybean-related compound ipriflavone has been shown to reduce bone loss in people suffering from osteoporosis.

With heart health, cancer prevention, and bone retention being soy's big claims to fame, the benefits of this bean appear to be endless.

Reference:
Carroll K. K., Review of clinical studies on cholesterol-lowering response to soy protein. J Am Diet Assoc 1991;1(7):820-27.