|Dark, medium or light roast - this is more than just a question of taste! The significant effect of roasting on the phenol-composition of coffee and the consequent health effects are rarely discussed.|
Now, to get the bad news out of the way, the study from the West-German Centre of Diabetes and Health in Düsseldorf which evaluated these effects unfortunately did so in 118 overweight subjects.
The good news, however, is that the subjects who were recruited by articles in local media in the region of Düsseldorf, Germany, were mostly overweight, not obese (BMIs of ≥27 kg/m²) came from various age-groups (18–69 years old) and - this is important - were regular coffee consumers (at least 3 cups/day), just like you (?). With them being weight stable and free of any acute of chronic diseases (with the exception of type 2 diabetes mellitus), they are thus not the ideal study group, but decent subjects - even though we will have to be careful when it comes to making conclusions with regard to the health effects of differently roasted coffee for leaner and healthier people.
In the introduction I already alluded to the purpose of this study. What I still have to do, though, is to tell you exactly what the scientists wanted to know and how they tried to find the answer to their question(s). From previous studies, Kempf et al. knew that dark roast coffee, which is rich in the trigenolline byproduct N-methylpyridinium (NMP: 785 mmol/L) and low in chlorogenic acid metabolites has significantly more pronounced weight loss effects in pre-obese (but not normal-weight) subjects; see Figure 1) than light roast coffee when it is administered at doses of 500ml/day in a 2x4-week cross over study (Kotyczka. 2011).
|Figure 1: Only the pre-obese subjects lost significant amounts of weight. A trend for higher greater weight loss in the dark roast phase of the cross-over study is however evident in all subjects (Kotcyzka. 2011).|
|A previously discussed problem with coffee is the formation of mold toxins, in particular ochratoxin A, when it's stored inappropiately. Luckily, roasting does - irrespective of whether you roast dark or light - sing. reduce the toxic mold (Van der Stegen. 2011).|
|Figure 2: Flow sheet of recruitment and analysis (directly from Kempf. 2015)|
|Table 1: Composition of medium roast (M)-coffee and dark roast (D)-coffee blends (Kempf. 2015).|
|Figure 3: In contrast to the short-term cross-over study, the long(er) term study suggests that lighter roasts have the more beneficial effects on potentially CVD- (HDL + trigs) and T2DM (Trigs + Adiponectin) serum markers (Kempf. 2015).|
- the significant increases in HDL and adiponectin, both of which have been linked to lower CVD and type II diabetes (T2DM) risk, which occurred in the medium roast group, and
- the likewise significant increase in triglycerides, of which scientists believe that they pave the way for both diabetes and heart disease, which occurred only in the dark roast group,
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- Greenberg, James A., Carol N. Boozer, and Allan Geliebter. "Coffee, diabetes, and weight control." The American journal of clinical nutrition 84.4 (2006): 682-693.
- Kempf, Kerstin, et al. "Cardiometabolic effects of two coffee blends differing in content for major constituents in overweight adults: a randomized controlled trial." European journal of nutrition (2014): 1-10.
- Muley, Arti, Prasad Muley, and Monali Shah. "Coffee to reduce risk of type 2 diabetes?: a systematic review." Current diabetes reviews 8.3 (2012): 162-168.
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- Kotyczka, Christine, et al. "Dark roast coffee is more effective than light roast coffee in reducing body weight, and in restoring red blood cell vitamin E and glutathione concentrations in healthy volunteers." Molecular nutrition & food research 55.10 (2011): 1582-1586.
- Onakpoya, I. J., et al. "The effect of chlorogenic acid on blood pressure: a systematic review and meta-analysis of randomized clinical trials." Journal of human hypertension 29.2 (2015): 77-81.
- Thom, Erling. "The effect of chlorogenic acid enriched coffee on glucose absorption in healthy volunteers and its effect on body mass when used long-term in overweight and obese people." Journal of International Medical Research 35.6 (2007): 900-908.
- Van der Stegen, Gerrit HD, Paulus JM Essens, and Joost Van der Lijn. "Effect of roasting conditions on reduction of ochratoxin A in coffee." Journal of Agricultural and Food Chemistry 49.10 (2001): 4713-4715.