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Could L-tyrosine and PCS prevent an asthma attack?

L-tyrosine, PCS, lungs, gut, Covid, Monash University, Australia, Research, bacteria, amino-acid, p-cresol sulphate, PCS, asthma, Professor, Benjamin Marsland, toxic, syndrome, Professor Benjamin Marsland
Could L-tyrosine and PCS prevent an asthma attack?

A common amino acid, L-tyrosine, is the precursor to a compound PCS in the body which seems to control inflammation in the lungs, that can lead to asthma and a poorer survival in Covid.

Monash University, Australia have been studying the gut-lung axis. Researchers first found, in previously published litterature, that these metabolites were in higher levels in people without asthma, when compared with those who had it.

When gut bacteria metabolised good quantities of the common amino-acid L-tyrosine, they produced p-cresol sulphate (PCS). Then they tested this with animals given asthma and found there was a “Profound and striking protection against asthma(1). Ordinarily, L-tyrosine is an amino acid associated with mental alertness.

Lead author Professor Benjamin Marsland, said that L-tyrosine is a well-known, safe amino acid already in use; but PCS is a molecule found in higher levels in patients with chronic Kidney disease and known to be toxic. Clinical trials would therefore be essential.

Interestingly, the researchers found that either compound gave ‘significant protection’ from lung inflammation and that the PCS travelled from gut to lung to act on the lining epithelial cells in the airways, and prevent asthma.

This was much the same with acute respiratory distress syndrome – ARDS is a major factor in Covid 19 deaths.

Professor Benjamin Marsland leads the Respiratory Immunology laboratory, where the main focus of research revolves around the microbiome in the gut, lung and skin and how it can influence respiratory diseases.



  1. Microbial Metabolism of L-tyrosine protects against allergic airway inflammation; 25 January, 2021, Nature Immunology