Light, moderate drinking may be good for eyes

Light to moderate alcohol consumption has the potential to lower the risk of cataract requiring surgery, and the protection is especially pronounced among wine drinkers, as shown in a study.

“This finding was consistent between two independent studies with contrasting methods of ascertaining alcohol intake,” according to the investigators. “The protective association was apparent whether any consumption of alcohol was compared to nonconsumption, and also whether the amount or frequency of alcohol intake was compared among drinkers only in dose-response analyses.”

The analysis included two cohorts, EPIC Norfolk (n=23,162; mean age, 59 years) and UK Biobank (n=469,387; mean age, 56 years). A total of 4,573 and 19,011 participants in the said cohorts underwent cataract surgery over a mean follow up of 193 and 95 months, respectively.

Compared with UK Biobank participants, those in EPIC-Norfolk were slightly older and more likely to be white, live in a less deprived area, have a lower body mass index, or have ever smoked. Conversely, the UK Biobank cohort had a greater proportion of alcohol drinkers (92 percent vs 81 percent).

Among drinkers, 67 percent, 55 percent, 53 percent, and 37 percent consumed red wine, white wine/champagne, beer/cider, and spirits, respectively, in UK Biobank; while 85 percent, 57 percent, and 53 percent consumed wine, beer, and spirits, respectively, in EPIC-Norfolk.

Multivariable Cox proportional hazards model showed an association between drinking versus abstinence and lower risk of cataract surgery both in UK Biobank (hazard ratio [HR], 0.89, 95 percent confidence interval [CI], 0.85–0.93) and EPIC-Norfolk (HR, 0.90, 95 percent CI, 0.84–0.97). [Ophthalmology 2021;doi:10.1016/j.ophtha.2021.02.007]

Interestingly, in EPIC-Norfolk, the greater the alcohol consumption, the higher the magnitude of protection (p<0.001). UK biobank, on the other hand, showed a U-shaped association. Among alcoholic beverage types, wine conferred the strongest protection, with the risk of incident cataract surgery being 23 percent and 14 percent lower among participants in the highest consumption category in the respective groups.

“The findings of our study have to be taken in the context of our primary outcome, cataract surgery, which is our surrogate for visually-significant cataract,” the investigators said. “Factors other than visual impairment may determine whether a person undergoes cataract surgery,” including access to healthcare, attitudes towards surgery, and the threshold of visual impairment, among others.

While unclear, alcoholic beverages may protect against cataract development via dietary intake of antioxidants, with plasma antioxidant activity previously shown to reduce cataract formation. Red wine, specifically, is abundant in resveratrol—a natural polyphenol with antioxidant properties. [Nonlinearity Biol Toxicol Med 2004;2:353-370; Nutrients 2012;4:759-781]

Another possible mechanism is via altered cholesterol levels. Alcohol drinking exerts favourable effects on low-density lipoprotein cholesterol (LDL-C), and LDL-C levels are positively associated with cataract risk. “Therefore, an increase in alcohol intake may lower the risk of cataract via reduced LDL-C,” the investigators noted. [PLoS One 2016;11e0148765; BMJ Open 2018;8e021496]

The current guidelines for safe alcohol intake quantity cite up to 14 units/week (equivalent to 112 g/week, with 1 unit corresponding to 8 g of alcohol) for both men and women in the UK, and 14 standard drinks per week (equivalent to 196 g/week, with 1 standard drink corresponding to 14 g of alcohol) for men and seven standard drinks per week (equivalent to 98 g/week) for women in the US. [https://health.gov/our-work/food-nutrition/previous-dietary-guidelines/2015; https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/545739/GDG_report-Jan2016.pdf]

“The range of maximum recommended alcohol intake is encompassed by the highest intake quartile in EPIC-Norfolk, [where] participants in the highest quartile consumed ≥88.78 g/week or 11.09 units/week. The results suggest that alcohol intake within the recommended range, in either the US or the UK, would be associated with a reduced chance of undergoing cataract surgery,” the investigators said.