It may be more crucial than researchers previously believed to consider specific nutrition advice based on individual genetic information, according to a study published in Ophthalmology. In particular, patients who are genetically at risk for glaucoma, may be well advised to avoid coffee and tea. Their morning cup may be putting their vision in danger. 

The investigation is the largest analysis yet regarding the impact of habitual caffeine consumption on intraocular pressure (IOP), and the first to examine whether genetic factors modify the impact of caffeine, according to the study. The research looked into caffeine intake in 121,374 participants in the United Kingdom Biobank. 

It employed the use of polygenic risk scores (PRS), which combines the influences of 111 genetic variants related to IOP. Participants who were in the highest IOP PRS quartile were 3.9 times more likely to develop glaucoma when they consumed 321 mg per day or more of caffeine, (P =.0003), the study shows. Researchers theorize that individuals with higher genetic risk may have reduced ability to handle occasional high IOP levels arising from caffeine intake.


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The participants ranged from 39 years to 73 years of age. At baseline, participants took a detailed questionnaire on the consumption of coffee and tea; provided saliva, urine, and blood samples; and gave consent for future scientific access to health records. Their IOP was measured with an Ocular Response Analyzer noncontact tonometer once for each eye, and averaged. Corneal-compensated IOP was used for the study. In addition, participants filled out the web-based Oxford WebQ 24-hour food frequency survey up to 5 times during a 3-year period.

When looking solely at dietary effects for participants who completed coffee and tea questionnaires and submitted WebQ surveys, researchers found no association between coffee or tea drinking with IOP. In fact, before taking genetics into account, those who consumed more than 231 mg of total caffeine had a 0.10 mm Hg lower IOP than those whose total caffeine intake was less than 87 mg per day (P-trend =.01). No associations were found between coffee, tea, or total dietary caffeine alone with glaucoma (P ≥0.05), and none specifically for primary open-angle glaucoma.

In total, 75,686 participants completed questionnaires, submitted WebQ surveys, and provided genetic data. In the lower 3 quartiles of IOP PRS — less genetic predisposition — greater use of caffeinated products showed no change or slightly lower IOP. In the highest quartile of IOP PRS, though, those in the lowest total caffeine intake group increased from the study population mean of 16.0 mm Hg to an average of 16.95 mm Hg, and participants with the highest level of caffeine consumption rose to an average of 17.3 mm Hg.

For tea, genetic factors played a significant moderating role for developing glaucoma. Researchers found that those who drank  3 to 6 cups of tea per day and were in the highest quartile of IOP PRS tendency had a 3-fold higher risk for glaucoma compared with those who did not drink tea and were in the lowest quartile of IOP PRS. Conversely, those who drank 3 to 6 cups a day and were in the lowest quartile of IOP PRS actually had a slightly lower risk for glaucoma, the study shows.

Limitations of this study included the relative subjectivity of questionnaires, and that the amount of caffeine in coffee varies by different types of beans and brewing styles. In addition, patients who live in the United Kingdom drink more instant coffee and tea, which are typically lower in caffeine than ground coffee. “Therefore, the association with IOP at the upper ranges in the United States diet remains unknown,” the study explains.

Disclosure: One study author declared affiliations with the pharmaceutical and biotech industries. Please see the original reference for a full list of authors’ disclosures.

Reference

Kim J, Aschard H, Kang J, et al. Modifiable risk factors for glaucoma collaboration, intraocular pressure, glaucoma and dietary caffeine consumption: a gene–diet interaction study from the UK Biobank. Ophthalmol. Published online December 14, 2020.   doi:10.1016/j.ophtha.2020.12.009.