FRIDAY, March 15, 2002 (HealthDayNews) -- A soy-based diet appeared to significantly ease pain and inflammation in a small study of rats, a finding that might someday translate into relief for millions of chronic pain sufferers.
The report by Johns Hopkins School of Medicine researchers, presented today at the annual meeting of the American Pain Society in Baltimore, raises hope for the potential alternative to potent pain-relief drugs like morphine.
But before you rush out to buy extra quantities of the standard soy sold in supermarkets and natural food story, be aware that the researchers say the soy in the study is not the same.
The American Chronic Pain Association reports that 86 million Americans suffer from some degree of chronic pain. The primary therapy remains the opioid family of drugs, including morphine, which while effective carries the risk of significant side effects, including addiction and severe constipation.
Lead investigator Jill Tall and her colleagues were collaborating with researchers from Israel, one of whom came to Johns Hopkins on sabbatical. An Israeli researcher had bred a specific strain of rats for use in studying pain, but when he attempted to perform his experiments on nerve injury pain at the Baltimore laboratory, he was surprised to find that the animals weren't experiencing as much pain as predicted by his research.
The team started ruling out factors that could be influencing the rats' pain response, and finally discovered that while in Israel, the rats were fed a diet based on casein, a dairy protein. However, the rat diet in the United States was based on soy protein.
"The animals that were being fed the soy protein here were not developing this robust and reproducible pain behavior, and the only difference was that soy protein," says Tall, a research fellow in anesthesiology and critical care at Johns Hopkins School of Medicine. "What at first was sort of frustrating for the laboratory turned out to be a whole new area of research."
Tall, who is primarily studying cancer pain, says that the mechanisms behind cancer pain are still not clearly understood and are a matter of debate among researchers. Some researchers have suggested that cancer causes pain resulting from tissue inflammation, while others say that cancer triggers nerve pain or pain from within bones.
In Tall's study, the researchers divided 20 rats divided into two groups: one was given the soy protein diet, the other got the dairy protein diet. After two weeks on the diets, the rats randomly got either an inflammatory solution or a placebo injected in a hind paw. The researchers then measured changes in paw thickness to determine inflammation.
They found that the rats on soy showed significantly less swelling than the rats on the dairy protein diet.
To test for pain response, the researchers tested how long the rats could withstand a heat stimulus on the injected paw, stopping short of causing any permanent damage to the rats' tissues. Again, the soy-eating rats exhibited a significantly higher pain tolerance compared to the casein group, withstanding more pain for a longer period of time.
But when the researchers tested response to pressure by measuring the reaction to nylon filaments placed at varying degrees of pressure against the injected paws, they found no difference between the groups.
"The beneficial effects of soy had no effect on that particular type of stimulus," says Tall, adding that that may suggest soy doesn't affect every type of nerve fiber.
Tall stresses that these findings are at a preliminary stage. "We are not at any point where we're ready to say this is an adjunct therapy."
The researchers are now looking in greater detail at the components of soy protein that could be creating this effect. But they anticipate that pain relief in the future could move beyond opioids like morphine and into complementary and alternative medicines that have been confirmed by science.
Tall says reducing pain is a critical part of improving quality of life. "Some individuals are suffering so much that suicide actually is something that enters someone's mind," she says. "I thank God that I've never experienced [so] much pain that you would actually consider ending your life."
She notes that many patients and physicians struggle with concerns about the risk of addiction associated with opioids. "That's also the reason why some pain goes untreated, because physicians often aren't taught extensively about pain."
But Tall adds, doctors are increasingly beginning to view pain as the "fifth vital sign," particularly since pain is often the primary reason people seek medical treatment.
What to Do: Find out more about pain from the American Pain Foundation, the National Institute of Neurological Disorders and Stroke, or the American Chronic Pain Association.
