While local ocular inflammation is characteristic of dry eye, this study found lower whole-body inflammation levels did not map onto DED risk. Photo: Getty Images.

Advice to adopt a Mediterranean diet has been a longstanding recommendation in many spheres of health care for its protective effects against various inflammation-mediated pathologies, dry eye included. In a bit of a surprise, a large Dutch study produced data counter to that tenet of ocular surface disease management.

The Women’s Health Study dry eye questionnaire was administered to 58,993 participants from the Dutch Lifelines Cohort with complete dietary data available; the cohort was 60% female and ranged in age from those 20 to 94 years old. Mediterranean diet level of adherence was assessed using a modified Mediterranean Diet Score (mMDS) and high-sensitivity C-reactive protein (hsCRP) was included as a biomarker of whole-body inflammation.

The study researchers found 9.1% of all included participants to display dry eye. However, the hypothesis that a Mediterranean diet decreases risk was not supported, as higher mMDS levels were actually associated with greater odds of dry eye, even after correction for factors of smoking status, BMI and other comorbidities. Also found was a significant relationship between increasing mMDS and lower circulating hsCRP levels, but no meaningful relationship was observed between hsCRP and dry eye.

In the discussion, the authors do note that their findings are similar to a previous study on male veterans, which also observed greater adherence to a Mediterranean diet was linked to greater odds of having dry eye. In the current study, the diet remained associated with symptomatic dry eye after excluding those with a diagnosis, reducing likelihood that reverse causality was a main explanation for these observations.

This study did find higher mMDS scores to be linked with lower hsCRP levels, indicating less overall inflammation, which is the exact reason the diet is thought to help with the disease at all. It is thought that adherence is anti-inflammatory in nature and has been shown to lower levels of pro-inflammatory markers in blood; but, the hsCRP levels were not indicated to map onto the likelihood of having dry eye like what might be expected. This specific finding did echo a prior study which observed no link between circulating CRP levels and tear function parameters or ocular symptoms, also in male veterans.

To this end, the authors mention that, “overall, although local ocular surface inflammation is a major driver of the vicious circle of DED, there appears to be no clear link between circulating CRP levels and dry eye symptoms in the general population, which may explain why the findings went against the initial hypothesis.”

To put succinctly, the authors add that their research has indicated “there appears to be no large population-wide protective effect against DED of adherence to a Mediterranean diet in the general population, despite its known anti-inflammatory effects.”

Magno MS, Moschowits E, Morthen MK, et al. Greater adherence to a Mediterranean diet is associated with lower C-reactive protein (CRP) levels, but not to lower odds of having dry eye disease. Ocul Surf. September 2023. [Epub ahead of print].