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Adding the amino acid tryptophan to fortified food distributed during international famine relief programmes could significantly reduce the number of deaths from malnutrition, according to the authors of a new study.

Their conclusion is based on the discovery of a molecular link between malnutrition and immune disorders in mice that may help explain why those suffering from malnutrition are susceptible to potentially fatal intestinal problems.

In a study published in Nature on 26 July, scientists from the Institute of Molecular Biotechnology in Vienna, Austria, and the University of Kiel, in Germany, describe how their conclusions emerged from research into the enzyme ACE2 (Angiotensin-converting enzyme 2) that affects cardiac and kidney function.

Experiments on mice revealed that ACE2 controls how the intestine absorbs amino acids from food, particularly the essential amino acid tryptophan, which cannot be synthesised by the body and must be obtained from the diet.

The scientists found that mice with insufficient levels of tryptophan experienced alterations in their immune systems, as well as changes to the type of bacteria found in the gut and bowels. Such changes made them more susceptible to intestinal inflammation and other potentially fatal conditions.

Both ACE2-deficient mice and mice fed a low-tryptophan diet were found to have reduced amounts of antimicrobial peptides – which are produced by the immune system to control the composition of intestinal bacteria communities – in their small intestines.

When fed a diet richer in tryptophan, intestinal balance of bacteria was restored. This reduced inflammation, confirming that changes to microbial communities in guts starved of tryptophan can induce intestinal problems.

According to Thomas Perlot, one of the study's lead researchers who is based at the Austrian institute, this discovery could have important implications for global strategies for tackling malnutrition, in particular for improving emergency famine relief strategies.

"If our discoveries hold true with humans, as well as with mice, the impact on malnutrition programmes could be far-reaching," Perlot told SciDev.Net.

"Emergency food relief programmes during famine outbreaks – for example, during the Horn of Africa famine last year – could simply add tryptophan as an additional dietary supplement," he said.

Suleman Qazi, an international nutrition consultant based in Pakistan, told SciDev.Net that the researchers now need to produce "some robust evidence, such as the results of clinical trials or of efficacy evaluations, before it is considered worth including in programmes tackling malnutrition."