June 23, 2025, 11:01 am | Read time: 6 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). Who should particularly avoid consuming soluble coffee…
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 thus contains 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 connection–and show that people with certain predispositions and of a certain age should particularly avoid the classic coffee.2
Follow the FITBOOK channel on WhatsApp now!
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 cases, the visual impairment can be so severe that 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 suggested a protective effect.4 However, these studies are often prone to biases.5,6 The current analysis therefore took a step further and used genetic methods to investigate whether a connection might exist–and whether it varies depending on the type of coffee.
Also interesting: The effect of black coffee on insulin levels
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
- Finngen Consortium (Finland): Genetic and medical data from over 300,000 people–including over 7,500 cases of dry AMD
Consumption was divided into three coffee variants in addition to general coffee consumption:
- 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: Examines 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. Individuals with a genetic predisposition to higher instant coffee consumption had an odds ratio (OR) of 6.92 for the occurrence of dry AMD–a clear correlation that persisted even after statistical correction. This could mean they have a 6.92-fold increased risk for 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 connection. 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–the so-called colocalization–examined whether the same genes influence both coffee consumption and AMD disease. Result: No common genetic origin could be detected. 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 thus potentially contains more harmful substances such as:
- Acrylamide: Formed during intense roasting and considered potentially carcinogenic.
- AGEs (Advanced Glycation Endproducts): Sugar-protein compounds that promote inflammatory processes and oxidative stress–both play a role in retinal damage.
These substances were not directly measured in the study, but are considered plausible explanations for the observed effect in research.
Who Are the Results Important For?
The results do not speak against coffee itself–but against instant coffee as a specific form. Relevant target groups could be:
- People with a known family history of AMD
- Individuals over 60 years old–as the risk of AMD increases with age
- People with high instant coffee consumption over many years
For these groups, it may be worthwhile to be more conscious of their coffee consumption and switch to other preparation methods.
Study Finds Ideal Amount of Coffee for Mental Health
Impatience Is Genetically Determined–and Linked to 212 Health Issues
Limitations of the Study
Only European Data Considered
The study is based solely on genetic and medical data from people of European descent. Whether the results can be applied to other population groups–such as those of Asian or African descent–remains unclear. For a general statement, future studies with a broader ethnic scope would be necessary.
Genetically Predicted Consumption–Not Actual Drinking Amounts
The researchers used so-called genetic instruments to predict how much coffee a person is likely to consume based on their genes. This is common practice in Mendelian randomization–but does not replace actual consumption data. How much coffee was actually consumed cannot be derived from this. Statements like “the risk increases from three cups a day” are therefore not possible.
Coffee Ingredients Not Directly Measured
The study does not examine the coffee itself, but genetic correlations. Chemical substances like acrylamide or AGEs, which can arise during the production of instant coffee, were not directly analyzed. The assumption that these compounds might be involved in the increased risk comes from other scientific works.
Preparation Methods Only Roughly Captured
The distinction between coffee types was limited to four broad categories: Soluble coffee, decaffeinated coffee, ground coffee, and total consumption. Differences in roast level, preparation (e.g., French press, espresso machine), additives, or drinking habits (e.g., with sugar or milk) were not recorded.
Conclusion
The new study shows: Not all types of coffee are equally rated in terms of health. While ground and decaffeinated coffee remained inconspicuous in the analysis, instant coffee was clearly associated with an increased risk of dry macular degeneration–one of the most common causes of severe visual impairment in old age.
For people at increased risk, it is worthwhile to consciously engage with their coffee consumption–and possibly switch to a gentler variant. The research thus makes an important contribution to a differentiated assessment of everyday habits–and to personalized prevention.