Researchers in the USA have discovered that reducing the amount of the L-glutamine amino acid in the body can block the growth of colorectal cancer tumors in mice. The first clinical trials on humans are due to begin this summer.

L-glutamine is a non-essential amino acid found in eggs, meat, fish, dairy products, cereals and pulses. It is also found in raw spinach and parsley, as well as Asian miso. It's sometimes recommended as a dietary supplement, notably for reducing intestinal permeability.

Recent research has established that cancerous tumors rely on L-glutamine to survive and grow.

In this latest study, scientists found that a subset of colorectal cancer cells containing a genetic mutation called PIK3CA -- a commonly occurring mutation in cancer cells -- were particularly high consumers of L-glutamine when growing.

When Professor Zhenghe John Wang and his team reduced the amount of L-glutamine available to these "mutant" cancer cells growing in laboratory dishes, the cells died.

This discovery, outlined in the journal Nature Communications, inspired the scientists to investigate the effects of depriving the cells of L-glutamine in mice with colorectal cancer tumors.

They found that when mice were given a compound to block the metabolism of L- glutamine, the tumors stopped growing. However, this effect was not seen in tumors that did not contain the PIK3CA mutation.

The findings, which are currently the subject of a patent application, could lead to the development of a new drug to suppress tumor growth.

The first clinical trials of an L-glutamine inhibitor in human patients with advanced stage colorectal cancer will begin this summer.

Over one million men and women are living with colorectal cancer in the USA.