Legumes and Soy for pain relief

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s Hopkins and Israeli Scientists Link Soybeans With Pain Relief

by Neuroscience Letters

ImmuneSupport.com

11-14-2001

Scientists from s Hopkins and two Israeli universities have

discovered another likely benefit of the much-touted legume,

soybeans: They may bring pain relief. A new study shows that

laboratory rats fed a diet containing soy meal develop far less pain

after nerve injury than their counterparts on soy-free diets. " In

people, strong individual differences exist in the perception of

pain, " says s Hopkins neurosurgeon N. , M.D., one

of the researchers. " And while this is undoubtedly due to a number of

factors, the idea that diet could affect the pain experience offers

fascinating possibilities for understanding our vulnerability to it. "

Enough similarities exist between rats and humans in the biology of

pain perception, says, to make them useful models. The

study, reported initially in a recent issue of the journal

Neuroscience Letters, since supported by additional research, arose

from unusual circumstances, says, when visiting Israeli

neuroscientist Yoram Shir of the Hebrew University of Jerusalem came

to Hopkins to further study an animal model for pain he'd previously

created with collaborators.

Shir's rats were treated to simulate serious painful syndromes that

can follow nerve injury in humans. Patients can develop a heightened

sensitivity to touch and temperature such that these normally mild

stimuli cause pain. Using anesthetized rats in which the sciatic

nerve to one foot is partly severed surgically, the Israeli

researchers measured sensitivity to pain by touching the foot with

fine probes of varied size.

But when Shir tried to duplicate his model at Hopkins, most of the

laboratory rats showed no heightened sensitivity to pain. " We were

mystified, " says .

Led by Shir, the research team then systematically tested every

possible source of difference in the model, from the strain of rat to

possible changes in surgical technique -- to the type of rat chow

used.

The conclusion: It was the rat chow. The American chow had higher

proportions of soy protein than the Israeli chow. When the

researchers returned soy-fed rats to a soy-free diet, the rats'

sensitivity to pain also returned. " These studies strongly indicate

that diet is an important factor in the expression of nerve-injury

pain in rats, " says Shir.

At this point, the scientists don't know what component of soy meal

suppresses sensitivity or what the mechanism could be. Certain soy

proteins may hamper the way cells relay messages internally,

says, or phytoestrogen plant hormones might be a culprit. " I suspect

answering these questions will give birth to a whole series of new

experiments, " he adds, " that could help explain why pain varies in

people, and help us develop new therapies. "

Models such as Shir's have recently sparked a quiet revolution in

scientists' ideas on pain: namely, that pain comes in a variety of

forms, each with a specific mechanism in the body. " The concept

explains why aspirin isn't particularly useful for pain from nerve

injury, for example, but works for inflammation, " says .

Scientists have recently shown that soybeans can lower cholesterol in

people. The vegetable is a source of omega-3 fatty acids and calcium

and supplies most of the essential amino acids people need to make

proteins. Soybeans also may lessen some symptoms of menopause, though

studies on that remain to be done.

All of the rat studies met NIH guidelines and have been approved by

institutional review boards of both institutions. The work was

supported by the USA-Israel Binational Science Foundation and by the

Hebrew University Center for Research on Pain.