Does drinking coffee help protect against developing type 2 diabetes?

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I read an interesting study this week that examined the relationship between changes in coffee and tea consumption and risk of developing type 2 diabetes over a 4-year period [1]. The authors found no association between tea consumption and diabetes risk, but it was a different story for coffee: increasing coffee consumption was associated with a reduced risk of type 2 diabetes over the 4-year study period. Also, overall, in individuals who reduced their coffee consumption, risk of diabetes went up.

The authors suggest that a possible explanation for the latter finding is ‘reverse causality’. Essentially, the idea here is that as people get sick, they then reduce their coffee consumption. In other words, illness leads to reduced coffee consumption, not the other way round. However, even then the analysis was performed to adjust for this (by excluding those with other illnesses), the results were pretty much the same.

The authors also found that the benefits associated with coffee consumption only existed for caffeine coffee (not decaffeinated). However, as they explain, decaffeinated consumption was generally low and the numbers of relevant people in the study may not have been enough to pick up any effect.

Other evidence ha founds a link between caffeinated coffee and reduced risk of type 2 diabetes (but no such link for decaffeinated coffee) [2].

Before we get too far ahead of ourselves, I feel it’s worth reminding ourselves here that these studies (so-called ‘epidemiological’ studies) cannot be used to conclude that drinking caffeinated coffee reduces the risk of type 2 diabetes (only that there is an association).

However, we do have some ‘clinical’ evidence that suggests that coffee may indeed be protective. In a study published in the American Journal of Clinical Nutrition, the effect of coffee-drinking on a variety of biochemical markers of disease was assessed [3].

A group of coffee drinkers were asked to abstain from drinking coffee for a month. The following month they were asked to drink four cups of coffee a day (a total of 600 mls of coffee a day). The month following this they were instructed to drink 8 cups of coffee a day.

Compared to drinking no coffee, drinking 8 cups a day was associated with significantly reduced levels of inflammatory markers (interleukin-18 and 8-isoprostane), as well as significantly raised levels of adiponectin. This hormone is secreted by fat cells, and has been shown to have generally beneficial effects on the body’s physiology including an ability to help the functioning of the hormone insulin. Broadly, these effects from drinking coffee would be expected to translate intorelative protection from type 2 diabetes.

While the evidence is not definitive, there is I think significant evidence that supports the idea that drinking coffee may help to reducerisk of succumbing to type 2 diabetes. There is some type 2 diabetes in my family, and I do drink coffee. I imagine I’ll continue to drink it (and enjoy it) for some time yet.


1. Bhupathiraju SN, et al. Changes in coffee intake and subsequent risk of type 2 diabetes:
three large cohorts of US men and women. Diabetologia DOI 10.1007/s00125-014-3235-7

2. Floegel A, et al. Coffee consumption and risk of chronic disease in the European Prospective Investigation into Cancer and Nutrition (EPIC)-Germany study. Am J Clin Nutr 2012;95:901-908

3. Kempf K, et al. Effects of coffee consumption on subclinical inflammation and other risk factors for type 2 diabetes: a clinical trial. Am J Clin Nutr 2010;91:950-957

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