In recent years studies have been reporting that caffeine in general, and coffee in particular, might bring health benefits. To take just one example, a piece published last year in JAMA, the journal of the American Medical Association, reported coffee was associated with decreased mortality. Other research has found a relationship between coffee and a lower risk of type 2 diabetes (T2D), some types of cancer, and gallstones.
Now a new study from researchers in Spain has investigated the possible relationship between caffeine consumption and the development of diabetic retinopathy (DR), a complication of diabetes that results from damage to the blood vessels of the retina, the light-sensitive layer of tissue at the back of the eyeball. Although one previous study did indicate that consuming more than two cups of coffee a day lowered the incidence of diabetic retinopathy, for the most part the results of previous investigations have been mixed, or, as the authors phrased it, “Overall, inconsistent results about the effect of caffeine intake and DR have been published.”
The new survey, “Caffeine and the Risk of Diabetic Retinopathy in Type 2 Diabetes: Findings from Clinical and Experimental Studies,” was published in the journal Nutrients. As the authors put it, “To our knowledge, this is the first study to assess the relationship between caffeine intake and DR-risk in subjects with T2D, as well as testing the effect of caffeine in an experimental diabetic model.”
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The researchers recruited 144 subjects who had diabetic retinopathy and 147 who didn’t and had them assessed by an expert ophthalmologist. One member of the research team individually administered to each participant a 101-item “validated food frequency questionnaire (FFQ)” that asked each subject how often they had consumed certain food items over the past year. Caffeine intake was calculated by including various sources. Nearly nine out of ten reported getting their caffeine through regular coffee, but other sources were light soft drinks, soft drinks, tea and infusions, decaffeinated coffee, chocolate, chocolate cookies, cakes, ice cream, liquors, dairy products, and cereals. The average age of the participants was around 60 and the male-female split was about 50/50. In addition to studying the dietary practices of humans, the researchers also experimented on mice. Twice daily for two weeks, half of a group of 20 mice were given one drop of caffeine in each eye, while the other half received non-caffeinated eye drops.
Caffeine appears to protect against diabetic retinopathy: study
The researchers reported, as they put it, “a higher frequency of subjects with DR in the lowest quartile of caffeine intake compared with individuals without DR,” although they “did not observe differences between groups in coffee and tea consumption.” They found no such improvements in the mice, however, although caffeine seemed to be related to a lower rate of what’s known as “vascular extravasation,” which is a kind of leakage that causes the retina to swell and impairs vision.
In summary, the authors said that in the study of humans, the adjusted model showed that moderate and high caffeine intake “had a protective effect” on diabetic retinopathy. “Our results,” they wrote, “suggest a dose-dependent protective effect of caffeine in the development of DR, while the potential benefits of antioxidants in coffee and tea should also be considered. Further research is needed to establish the benefits and mechanisms of caffeinated beverages in the development of DR.”
Want to learn more about keeping your eyes healthy with diabetes? Read “Diabetic Retinopathy: What You Need to Know,” “Diabetic Eye Exams: What to Know,” “Eating for Better Vision and Healthy Eyes.”
