Jesús Vioque
Professor of Preventive Medicine and Public Health and Director of the Unit of Epidemiology of Nutrition at the University Miguel Hernández
This is an interesting study that analyses data from several cohort studies conducted mainly in a European population in which plasma levels of caffeine were estimated genetically and shows a protective association against high body mass index and the incidence of type 2 diabetes. The study has carried out a sophisticated analysis based on Mendelian randomisation, a type of analysis that attempts to overcome the limitations of observational studies by simulating a randomised intervention study.
The results would somewhat support the well-known protective effect of moderate coffee consumption on the risk of developing and dying from the main non-communicable diseases (cancer, cardiovascular, diabetes), also evidenced in Spanish cohort studies. However, some important aspects remain unclear, such as to what extent the plasma level represents habitual caffeine consumption and what proportion is due to coffee consumption or to the consumption of other foods such as chocolate or caffeinated sweetened beverages that also contain other unhealthy nutrients.
It would have been interesting to see the role of coffee consumption and other caffeine-containing foods included in the causal model depicted in the graph. After all, it is these foods that are consumed and on which dietary recommendations can be made.
In any case, the study provides very interesting evidence that needs to be further investigated.