The research study Coffee and Caffeine Ameliorate Hyperglycemia, Fatty Liver, and Inflammatory Adipocytokine Expression in Spontaneously Diabetic KK-Ay Mice aims to determine the possible preventive effects of caffeine on the development of hyperglycemia. To conduct the study, the researchers used the following materials: regular black coffee, diluted caffeine, and Four-week-old male KK-Ay mice. The hypothesis can be crystallized as the following statement: “habitual consumption of caffeine decreases the risk of type 2 diabetes”. Therefore, the caffeine consumption is the independent variable, and the risk of type 2 diabetes is a dependent one.
The involvement of animals is typical for epidemiological studies of this sort. Such design allows to control several factors that would be uncontrollable or much more difficult in case of humans: environment, diet, and, to a certain extent genetic factors. Not to mention, that more complex ethical constraints rise in the case of involving humans. (Silman & Macfarlane, 2002)
The study composed of two experiments. In the first one, the mice were given diluted black coffee and, in the second experiment, the researches use the caffeine solution. In both parts of the study, there was a control group of mice who drank water. The experimental procedures were followed by the analysis of effects that included the insulin tolerance test, RNA Preparation and Expression Level Analysis, and the analysis of metabolic parameters. Test results were converted into statistical data.
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The research reached the finding of an antidiabetic effect of coffee consumption. The issue is, however, that the researchers could not determine definitely which particular component of the coffee had a positive effect. Their publication acknowledges previous research findings of the positive effects of decaffeinated coffee on insulin sensitivity. (Shearer et al., 2007) Thus, from the point of view of research design, the study failed to determine the correct independent variable. This limitation leads to the risks of statistical biases and the false choice of one of the several possible explanatory variables. It is not uncommon to have a multiple-variable situation in epidemiology, but it is important to evaluate the relevance of specific variable to strengthen the potential for practical use of the study findings and eliminate any limitation. (Woodward, 2013)
The study is certainly a significant contribution to the research on antidiabetic compounds. In my view, it will induce more interest on the exploration of specific effects of caffeine and other coffee components.
- Shearer, J., Sellars, E. A., Farah, A., Graham, T. E., & Wasserman, D. H. (2007). Effects of chronic coffee consumption on glucose kinetics in the conscious rat. Canadian journal of physiology and pharmacology, 85(8), 823-830.
- Silman, A. J., & Macfarlane, G. J. (2002). Epidemiological studies: a practical guide. Cambridge University Press.
- Woodward, M. (2013). Epidemiology: study design and data analysis. CRC Press.
Yamauchi, R., Kobayashi, M., Matsuda, Y., Ojika, M., Shigeoka, S., Yamamoto, Y., … & Horio, F. (2010). Coffee and caffeine ameliorate hyperglycemia, fatty liver, and inflammatory adipocytokine expression in spontaneously diabetic KK-Ay mice. Journal of agricultural and food chemistry, 58(9), 5597-5603.
