A daily cocktail of prebiotics and probiotics may help treat fatigue, memory loss and gastrointestinal upset in people with long covid – a condition where people experience lingering symptoms for months or years after contracting covid-19.
While long covid is poorly understood, previous research has shown that people with the condition have lower levels of certain gut microbes than those without. In particular, they lack gut bacteria that produce compounds called short-chain fatty acids, which regulate immune responses.
Siew Ng at the Chinese University of Hong Kong and her colleagues concocted a mixture to boost short-chain fatty acid production. Called SIM01, it contained three probiotics – live strains of bacteria – and three prebiotics, compounds that help beneficial gut microbes grow.
They gave the cocktail to 232 adults; another group of 231 adults took a mixture containing starch and low-dose vitamin C. Both mixtures were taken twice daily for six months. All participants lived in Hong Kong, had previously tested positive for covid-19 and met the US Centers for Disease Control and Prevention’s criteria for long covid.
Researchers used a questionnaire to assess 14 long covid symptoms in participants before the treatment began and after it stopped. At the end of the trial, they found that people given SIM01 were, on average, about 2 to 2.5 times more likely to experience alleviation of five long covid symptoms – fatigue, memory loss, difficulty concentrating, general unwellness and gastrointestinal upset. The team also found no significant side effects of the therapy.
Analysis of faecal samples collected before and after the trial revealed SIM01 enhanced the diversity of gut microbes and fostered the growth of beneficial gut bacteria, says Ng. Therefore, it could potentially help treat other conditions that have been linked to disrupted gut microbiomes, such as chronic fatigue syndrome, she says.
How these changes in the gut alleviate long covid symptoms is ambiguous, though, says Timothy Sampson at Emory University in Georgia. “While it does make sense that the microbiome has the capacity to mediate immune responses… it is not clear that the [immune system] is what is actually underlying the [long covid] symptoms,” he says.