Coffee - Different Roasts, Different Health Effects | Darker Roasts Better for Weight Loss, Lighter Roasts Healthier!?

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.

You may remember my often misinterpreted article about bullet-proof coffee in which I actually defended the fad by providing evidence that the negative effects on blood lipids may actually be cause by not filtering the coffee vs. putting butter into it (read it). Well, today I would like to dig a bit deeper into the differential effects not of coffee brewing, but rather of coffee roasting on the of your favorite beverage's major active ingredients and its subsequent effects on your health.

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).

Now, 4 weeks is not an acute study, but it's not exactly long enough to observe things like ceiling effects or the well-known "too much of a good thing" effect that may occur when agents with proven short-term benefits are administered over long(er) time periods.
Against that background, you'd probably agree with Kerstin Kempf and her colleagues who thought it would be interesting to see "whether these effects on body weight would also be detectable after a longer-term consumption of dark roast coffee, in particular, in overweight adults" who are at the highest risk of dietary induced metabolic deteriorations (Kempf. 2015).

Figure 2: Flow sheet of recruitment and analysis (directly from Kempf. 2015)

In their randomized controlled trial, Kempf et al. compared the effect of 3-months consumption of (1) a medium roasted coffee blend rich in CQA and trigonelline versus a dark-roasted coffee blend rich in NMP (see Table 1 for the concentration of CQA, which is the sum of 3-, 4- and 5-caffeoylquinic acids, chlorogenic acid metabolites; NMP N-methylpyridinium, trigonelline and caffeine), as well as of (2) both groups combined for an estimate of general effects of coffee on body weight and selected cardiometabolic risk factors like HDL, LDL, triglycerides, adipokines (leptin, adiponectin), etc..
During the study, the participants consumed an average of 4–5 cups per day of the roast they had been randomly assigned to. Even though that's probably more than the 500ml in the previously cited study by Kotcyzka et al. (see Figure 1) this was not enough coffee to exert significant effects on either the mean body weight, the body mass index or the waist circumference of the participants; and that's irrespective of whether the they consumed the dark (D) or medium (M) roast.

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).

Due to the different effects on some health-relevant metabolic markers, though, the study results are still SuppVersity news-worthy: In spite of the fact that the systolic blood pressure, which is obviously also a health relevant maker, decreased in the dark roast coffee group only (p < 0.05), other changes, in particular the contrast between

• 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,

would suggest health benefits of choosing lighter over darker roasts. How relevant those are for someone with perfect cholesterol and triglyceride levels may yet be questionable, also because neither of the two roasts affected the subjects' glucoregulation, or insulin levels (the scientists did observe an increase in the long-term glucose measure HbA1c (+0.1%), but this increase was identical in both groups and so marginal that it's hardly physiologically relevant).
References:

• Crozier, Thomas WM, et al. "Espresso coffees, caffeine and chlorogenic acid intake: potential health implications." Food & function 3.1 (2012): 30-33.
• del Castillo, María Dolores, Jennifer M. Ames, and Michael H. Gordon. "Effect of roasting on the antioxidant activity of coffee brews." Journal of Agricultural and Food Chemistry 50.13 (2002): 3698-3703.
• 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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• Nicoli, M. C., et al. "Antioxidant properties of coffee brews in relation to the roasting degree." LWT-Food Science and Technology 30.3 (1997): 292-297.
• 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.