Dry eye disease: Too much water intake more harmful than beneficial

Drinking a lot of water does not seem to lower the risk of dry eye disease (DED) but may rather contribute to a modest risk increase, as reported in a recent cross-sectional study.

A team of investigators from Oslo University Hospital in Norway and University Medical Center Groningen in the Netherlands looked at 51,551 participants from the population-based Lifelines cohort (mean age 51.2 years, 60.5 percent female, 98.7 percent European White) and found that higher water intake was associated with an increased prevalence of Women's Health Study (WHS)-defined DED (odds ratio [OR], 1.011 per 100 ml/day, 95 percent confidence interval [CI], 1.004–1.017; p=0.003). [Acta Ophthalmol 2022;doi:10.1111/aos.15227]

Even after excluding participants with clinical DED, the analysis still showed that drinking greater amounts of water conveyed a higher likelihood of having DED symptoms (OR, 1.010 per 100 ml/day, 95 percent CI, 1.006–1.015; p<0.001).

The same was true for higher 24-hour urine volumes – a biomarker of hydration status – with each 100 ml/day increment in urine volume correlating with a 1-percent increase in the risk of WHS-defined DED (OR, 1.010, 95 percent CI, 1.005–1.015; p<0.001).

These associations persisted when beverage water and food water were assessed separately.

“While greater water intake has been associated with health benefits in other general populations, such as lower risk of nonalcoholic fatty liver disease and chronic kidney disease, this large epidemiological study did not find it to be associated with a reduced risk of having DED,” according to the investigators. [Eur J Clin Nutr 2021;75:801-1808; Medicine 2021;100:e26009]

“The European Food Safety Authority recommends daily intake of food and beverage water of 2.0 L/day for females and 2.5 L/day for males, but no upper limit was defined. This includes water from all food and beverage sources, but excludes metabolic water,” they noted.

In this study, 74.5 percent of men and 39.8 percent of women did not meet the said water intake recommendations. The investigators used this cutoff in a sensitivity analysis and obtained results similar to that of the primary analyses. That is, water intake above the cutoff was positively associated with WHS-defined DED.

There is no substantial literature to establish a biological link behind the relationship between habitual hydration and DED. Yet, the investigators noted that some clinicians recommend drinking more water as supplemental therapy for dry eye. Additionally, the internet perpetuates the claim that drinking water is beneficial for dry eye, with some of the information even suggesting that improving whole-body hydration through fluid intervention could have a therapeutic effect on dry eyes. [Invest Ophthalmol Vis Sci 2012;53:6622-6627; J Med Internet Res 2013;15:e220]

“Due to this, patients may be inclined to think that increasing water intake would alleviate dry eye symptoms,” they said.

Based on the present data, the investigators deemed that advising dry eye patients to increase their water intake to be unjustifiable. They called for interventional studies to fully understand any effect of water consumption on dry eye.