Dry Eyes

A surprising finding in mice with no gut bacteria at all

Dry eye disease has an inflammatory component, and researchers have increasingly looked to the gut for part of the explanation. In one striking experiment, mice bred to have no gut bacteria at all developed worse Sjögren-like dry eye symptoms than normal mice with an intact microbiome, direct evidence that gut bacteria play a genuinely protective role at the eye's surface, not just a coincidental association.

Confirmed in people with Sjögren's syndrome

Human studies point the same way. A study comparing people with Sjögren's syndrome, an autoimmune condition that causes severe dry eyes and dry mouth, against people with ordinary dry eye and healthy controls found clear differences in gut bacteria. People with Sjögren's had reduced levels of several beneficial bacteria, including Blautia and Bifidobacterium, and these differences correlated directly with how severe their dry eye symptoms were, not just with having the diagnosis in general.

Source: Gut dysbiosis is prevailing in Sjögren's syndrome and is related to dry eye severity

Mixed results when probiotics are tested directly

A double-masked, randomised controlled trial gave 41 people with dry eye either a probiotic and prebiotic combination or a placebo for 4 months. The treatment didn't significantly improve the physical signs doctors measure, such as corneal staining, though this trial specifically excluded people with Sjögren's syndrome and included people with milder disease at the outset, precisely the group researchers think might benefit most given how much more disrupted gut bacteria are in Sjögren's. This is an honest, mixed result rather than a clear win, and it suggests any benefit may depend heavily on who's being treated. As with any probiotic, a supplement also only works if the bacteria it introduces are properly fed afterward with fibre, something a 4-month trial can't fully capture if participants' broader diets weren't part of the intervention.

Source: The Impact of Probiotics and Prebiotics on Dry Eye Disease Signs and Symptoms

What this means for you

Persistent dry eyes, especially alongside dry mouth, joint pain, or fatigue, are worth raising with a doctor, since these can be early signs of Sjögren's syndrome or another underlying condition rather than simple environmental dry eye. Standard treatments, including artificial tears and addressing any underlying cause, remain the established first step. Given the strength of the mouse evidence and the link to symptom severity in Sjögren's, a varied, plant-rich diet that supports a diverse gut microbiome is a reasonable, low-risk addition alongside standard care, particularly for anyone with a diagnosed autoimmune dry eye condition. That's the same idea behind GutLab, everyday gut health starts with regularly feeding the microbiome a broad range of plant-rich ingredients.