A cheap supplement could help protect against pesky winter viruses, including this season’s new ‘super flu,’ a study suggests.
Methionine is an essential amino acid that builds molecules needed for cell and DNA function throughout the body.
It has been shown to help produce antioxidants, which banish harmful molecules called free radicals and help fight diseases, and help the body absorb vital nutrients.
However, the body cannot produce methionine on its own. While eggs, fish and lean meats are the richest source, it can also be found in supplements, which are typically sold as L-methionine and costs about $1 per pill.
In a new study, researchers in California tested the over-the-counter supplement on mice with systemic inflammation, a common sign of infection.
They found that mice who were fed methionine supplements has increased kidney filtration and blood flow, which helped their bodies flush out cytokines, immune proteins that induce inflammation to fight threats.
Though the inflammation from cytokines responds immune system threats, it can become uncontrolled and lead to organ damage and sepsis, an immune system overreaction to infects that attacks healthy organs and tissues.
Mice that received methionine, however, were protected against infection without excess cytokines.
Methionine supplements have been shown to protect against infections and inflammation in a new study (stock image)
The researchers, from the Salk Institute for Biological Studies in California, believe methionine helps boost kidney function, which helps the kidneys flush out cytokines.
They also suggested methionine supplementation may be able to be adapted for treating chronic kidney conditions.
Dr Janelle Ayres, senior study author and professor at the Salk Institute for Biological Studies, said: ‘Our study indicates that small biological differences, including dietary factors, can have large effects on disease outcomes.’
A bottle of L-methionine supplements costs between $10 and $30 for a 30-day supply, depending on the brand. This averages out to 30 cents to $1 per pill.
The findings, published earlier this month in the journal Cell Metabolism, comes amid a surge of influenza in the US. This year’s new strain, H3N2 subclade K, or ‘super flu,’ has infected 15 million Americans, hospitalized 180,000 and killed 7,400, the CDC estimates.
And the latest figures, which run through January 17, show that those deaths include 44 children, 12 of whom died this past week.
The study looked at mice who were given systemic inflammation from the bacteria Yersinia pseudotuberculosis, which causes gastrointestinal infections in humans, largely in children.
The team noticed that infected mice were not eating as much as their healthy counterparts and had lower levels of methionine.
The researchers then fed a new batch of mice methionine supplements, which boosted their kidney function and lowered their cytokine levels while still fighting off infection.
They also found that mice with sepsis and kidney injuries showed improvements in their condition after receiving methionine.
The above map shows viral activity levels of the flu in each state as of January 17, 2026
Recent CDC data reveals a divergence in flu activity: while hospital admissions for adults have decreased, children and adolescents aged 5 to 17 are visiting emergency departments more frequently
Dr Ayres said: ‘Our discovery of a kidney-driven mechanism that limits inflammation, together with the protective effects of methionine supplementation in mice, points toward the potential of nutrition as a mechanistically informed medical intervention that can direct and optimize the paths people take in response to insults that cause disease.’
The experts believe that by helping the mice’s bodies flush out cytokines, methionine prevented whole-body inflammation that can lead to organ damage and sepsis.
Dr Katia Troha, first study author and postdoctoral researcher in Ayres’ lab, said: ‘Pro-inflammatory cytokines are ultimately what leads to sickness and death in a lot of cases.
‘The immune system has to balance inflammation to attack the invader without harming healthy cells in the body. Our job is to find the mechanisms it uses to do that, so that we can target them to improve patient outcomes.’
The researchers cautioned that the findings are early and may not have the same results in humans. Follow-up studies are needed, but the team says the initial findings are promising.
Dr Ayres said: ‘Our findings add to a growing body of evidence that common dietary elements can be used as medicine.
‘By studying these basic protective mechanisms, we reveal surprising new ways to shift individuals that are fated to develop disease and die onto trajectories of health and survival.
‘It may one day be possible for something as simple as a supplement with dinner to make the difference between life and death for a patient.’
