Soy diet may help manage pain

“Studies have shown that chronic pain patients are undertreated due to physicians’ lack of proper and full education about pain management, in addition to the physicians’ concerns about the addictive properties of morphine and opiates and the tendency for patients to build up a tolerance to the medication over time,” says Jill M. Tall, a lead author of the unpublished study and a postdoctoral fellow in Johns Hopkins Medical Institutions’ division of anesthesiology and critical care medicine.

Chronic pain is a condition suffered by millions of Americans, and it often leads to partial or complete disability, according to the Centers for Disease Control and Prevention. Although the underlying cause of pain may vary, many cases share the feature of inflammation. Besides causing edema (accumulation of excess fluid under the skin), inflammation also causes hyperalgesia, an enhanced response to painful stimuli such as heat and pressure.

Under the direction of Srinivasa N. Raja, Hopkins’ director of pain research, Tall and her colleagues tested 2 groups of 10 rats each. For 2 weeks, one group was fed a diet based on soy protein and the other a diet based on casein (a milk protein found in cheese). Researchers randomly injected each rat’s hind paw with either a placebo or a solution designed to cause inflammatory pain. Researchers measured inflammation and fluid buildup in the afflicted paw and then tested pain tolerance in the paw by applying heat. Finally, they applied a series of nylon filaments to the paw to test pressure sensitivity. These tests were repeated 6, 24, 48, and 96 h after the injection.

“Our results showed that the edema and fluid buildup were less in the animals on the soy protein diet in comparison to other animals,” Tall explains. “We also found that animals consuming soy were able to tolerate the heat stimulus longer. The two groups showed no difference in reaction to the pressure stimulus.” Tall and her colleagues plan to publish this study in the near future.

“While stressing that this is a preclinical animal model, we are finding that there are dietary influences that can have a positive effect on pain management,” says Tall. “Hopefully in the future, we will have complementary and possibly alternative therapies to offer chronic pain sufferers.”