This is going to offer some additional therapies in managing pain and inflammation

Dr Jill Tall

Study co-author Dr Jill Tall said: "I was sceptical to say the least when I began my work in the lab looking at complementary and alternative therapies for pain.

"But for humans in the long run, this is going to offer some additional therapies in managing pain and inflammation."

Managing chronic pain is difficult and tends to be based on morphine, which produces side effects such as constipation, which often become too painful for patients to tolerate.

Researchers gave 10 rats a soya protein diet and another 10 a milk protein one.

The rats were then randomly given either a placebo or a solution that would cause inflammation in the rat's hind paw.

Alternative therapies

Dr Tall and her colleagues at the John Hopkins University in Baltimore, USA, measured paw thickness to gauge fluid build-up.

Pain tolerance was measured by assessing how long rats could tolerate pressure and heat stimulus before removing their paw from the heat source.

Rats given the soya protein had "significantly less" swelling in their paws and were able to withstand more pain for a longer period than the milk protein group.

Dr Tall said: "Our generation is very open to the idea of dietary methods of pain control.

"We hope to find complementary and alternative treatments to help people suffering from pain."

However, she said more research would need to be carried out to determine whether the soya protein works in humans, and if it is effective.

Further studies would determine if a soya diet could reduce the morphine doses needed for treating chronic pain and therefore the side effects related to the medication.