June 23, 2025, 11:01 am | Read time: 5 minutes
Instant coffee is considered practical, quick, and popular worldwide. But how does its consumption affect our health—especially vision in old age? A new large-scale genetic study provides intriguing insights: Regular consumption of instant coffee may be linked to a significantly increased risk of dry age-related macular degeneration (AMD). Other types of coffee, such as filtered or decaffeinated, did not show this effect.
Coffee is a daily staple for many people. Studies even show certain health benefits, such as for the heart or liver.1 However, not every type of coffee affects the body in the same way. Possible reasons for the differences in effects could be the method of production or preparation. Instant coffee, or soluble coffee, is made through a special industrial process and therefore contains some different chemical substances than freshly brewed filter coffee. A Chinese research team investigated whether this particular variant is associated with a higher risk of dry AMD, one of the most common causes of blindness in old age. The results provide the first genetically based evidence of a possible causal link and cast a popular everyday classic in a new light.2
Overview
What Does Coffee Consumption Have to Do with Eye Health?
Age-related macular degeneration (AMD) is a chronic disease of the central retina, where central vision gradually deteriorates. Affected individuals can no longer recognize faces or read books—in advanced stages, it is classified as “blindness.” The most common form is dry AMD, for which there is currently no curative therapy. This makes potential preventive measures all the more important.3
Previous observational studies have yielded conflicting results on the impact of coffee—some even saw a protective effect.4 However, these studies are often prone to bias.56 The current analysis, therefore, took a step further and used genetic methods to investigate whether a connection might exist.
Study Design: How the Researchers Proceeded
The researchers used data from two large health databases:
- UK Biobank: Information from over 800,000 people on coffee consumption
- UK Biobank: Genetic and medical data from over 300,000 people—including more than 7,500 cases of dry AMD
Coffee consumption was divided into three variants:
- Total consumption
- Decaffeinated coffee
- Ground coffee
- Instant coffee (soluble coffee)
Three genetic epidemiological methods were used to examine whether there is a connection with AMD:
- LDSC: Tests whether there is a genetic overlap between two traits—here, for example, between “coffee consumption” and “AMD.”
- Mendelian randomization: Tests whether people with a genetic predisposition to higher consumption also develop AMD more frequently, which would suggest a possible causal effect.
- Colocalization: Analyzes whether the genetic causes of both traits lie in the same section of the genome.
Key Findings of the Study
Only Instant Coffee Shows a Clear Risk Correlation
The analysis showed that only soluble coffee was significantly associated with an increased risk of dry AMD. People with a genetic predisposition to higher instant coffee consumption had an odds ratio (OR) of 6.92 for developing dry AMD—a significant correlation that persisted even after statistical correction. This could mean they have a 6.92 times higher risk of this eye disease.
No Increased Risk with Filter or Decaffeinated Coffee
Other coffee variants, including decaffeinated coffee, ground filter coffee, or general coffee consumption, showed no comparable association. Even among people with a high genetic predisposition to these variants, no statistically significant effect on AMD risk was found, nor was there any effect on wet AMD, the rarer but more aggressive form.
No Shared Genes for Coffee and AMD
Another part of the analysis—called colocalization—examined whether the same genes influence both coffee consumption and AMD. The result: No common genetic origin could be demonstrated. This suggests that the observed connection cannot be explained by a single “risk gene” but is likely a complex interplay of genetic predisposition, environmental factors, and biological processes (such as inflammation or oxidative stress).
Why Instant Coffee? What Makes It Different?
The researchers suspect that the difference lies in the production process: Soluble coffee is processed at very high temperatures and therefore potentially contains different chemical substances, such as:
- Advanced Glycation Endproducts (AGEs): Sugar-derived compounds that can contribute to inflammation and oxidative stress, potentially affecting eye health.
- Acrylamide: A chemical that can form in some foods during high-temperature cooking processes, such as frying, roasting, and baking.
These substances may contribute to the increased risk of retinal diseases like dry AMD.
Who Should Pay Attention to These Results?
The study is particularly relevant for:
- People with a high genetic predisposition to dry AMD
- Individuals who consume large amounts of instant coffee over many years
- Older adults, as the risk of AMD increases with age
For these groups, it may be wise to be more mindful of their coffee consumption and consider alternatives.
Limitations of the Study
Only European Data Considered
The study is based solely on genetic and medical data from European populations. Broader studies are needed to include a more diverse range of participants to confirm these findings.
Genetically Predicted Consumption – Not Actual Drinking Amounts
The study relies exclusively on genetic correlations rather than actual consumption data. While Mendelian randomization is a useful tool, it does not replace real consumption data. The actual amount of coffee consumed cannot be determined from this method alone.
No Shared Genes for Coffee and AMD
Another part of the analysis—the so-called colocalization—examined whether the same genes influence both coffee consumption and AMD. The result: No common genetic origin could be demonstrated. This suggests that the observed connection cannot be explained by a single “risk gene” but is likely a complex interplay of genetic predisposition, environmental factors, and biological processes (such as inflammation or oxidative stress).
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Conclusion
The new study shows that not all types of coffee are equally healthy. While ground and decaffeinated coffee remained unremarkable in the analysis, instant coffee was clearly associated with an increased risk of dry macular degeneration, one of the most common causes of severe vision impairment in old age.
For these groups, it may be wise to be more mindful of their coffee consumption and to consider personalizing daily habits for a more nuanced assessment of everyday habits and personalized prevention.