Coffee May be Linked to Reduced Risk of Type 2 Diabetes

By Lainey Younkin, RD

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What began in the jungles of Ethiopia several hundred years ago now presents itself on every corner in both cities and suburbs.  It’s sold at Starbucks, Dunkin Donuts, Panera, and Au Bon Pain among others, and Americans rely on it to fuel their bodies and brains each day.  It’s one of the most popular nonalcoholic beverages in the world.  You guessed.  It’s coffee.

Coffee originates from coffee cherries whose seeds are roasted, creating a complex chemical composition.  Its makeup consists of over a thousand different chemicals including caffeine, chlorogenic acid, other polyphenols, carbohydrates, lipids, vitamins, minerals, nitrogenous compounds, and many others.

Coffee consumption has skyrocketed in recent years due to these “fast coffee” chains that are ever-present.  But with coffee’s growing popularity has come growing speculations about its effect on health.  Specifically, researchers have been interested in the effect of coffee on chronic disease risk, and according to a recent German study they may be one step closer to finding a link.

The European Prospective Investigation into Cancer and Nutrition (EPIC)-Germany Study results showed that coffee consumption does not increase the risk of chronic disease (type 2 diabetes, myocardial infarction, stroke, and cancer) but could lower the risk of type 2 diabetes (T2D).

The EPIC-Germany Study sought to determine the effects of caffeinated and decaffeinated coffee consumption on the risk of four chronic diseases: T2D, myocardial infarction (MI), stroke, and cancer. Participants were from two cities in Germany that are part of the larger EPIC study, a multicenter prospective cohort focused on associations between diet, lifestyle, and chronic disease risk.

Previous studies yielded conflicting results surrounding coffee’s effect on chronic diseases.  Some studies suggest that drinking coffee raises the risk of many chronic diseases.  Randomized controlled trials have shown coffee consumption raises blood pressure, cholesterol levels, and homocysteine.  Other studies suggest coffee reduces the risk of chronic diseases, and still others claim there is no association.  Current dietary guidelines recommend drinking coffee in moderation, and the American Heart Association says that 1-2 cups per day does not seem to be harmful in relation to coronary heart disease.

One reason results are conflicting is because many factors must be taken into consideration when addressing this potential relationship.  Several previous studies did not differentiate between caffeinated and decaffeinated coffee.  Other studies failed to account for confounding variables such as smoking, alcohol intake, and physical activity.  Historically, smoking and coffee consumption have gone hand-in-hand, which presents the question of which is to blame for adverse health outcomes.

The EPIC-Germany Study analysis included 42,659 participants (mean age 49.7 y) recruited from 1994-1998 and followed for almost nine years.  Compared to drinking <1 cup/d of caffeinated coffee, they found that consuming >4 cups/d of caffeinated coffee was associated with a 23% lower risk of T2D.  The same amount of decaffeinated coffee (>4 cups/d) was found to be associated with a 30% lower risk of T2D.  One cup of coffee was defined as 150 mL, which is slightly more than 4 oz.

In addition, compared to drinking <1 cup/d of decaffeinated coffee, consuming >4 cups/d was positively associated with MI risk.  But, the investigators were quick to point out that this finding must be taken with caution since only 4.5% of the participants reported drinking solely decaffeinated coffee.  Also, it was likely that participants could have switched to decaffeinated coffee after diagnosis of CVD.  Therefore, the positive association could be due to the fact that participants already had an increased risk of MI from having had a previous heart attack.

All of these results were after adjustment for confounding factors including chronic disease risk, age, sex, city, alcohol intake, smoking status, BMI, and hypertension.

The researchers also found an interaction between drinking caffeinated coffee and smoking. For smokers, caffeinated coffee consumption did not decrease the risk of T2D. This is likely because the adverse effects of smoking may outweigh the potential benefits of coffee.

Prior to previous reports, the researchers found no relationship between caffeinated and decaffeinated coffee consumption and CVD risk. They believe this is due in part to previous studies not adjusting for smoking and alcohol intake.  Since this was an observational study, causality could not be determined.  The researchers also found no relationship between caffeinated or decaffeinated coffee consumption and total cancer risk.

While this study took both caffeinated and decaffeinated coffee into account, it had a few limitations.  It relied on self-reported coffee consumption, did not assess the method of preparation, and did not determine if anything was added to the coffee (sugar, milk, etc).

Clearly, more studies are needed on this hot topic.  Until further research proves otherwise, drink away, in moderation.

*Sources available on request

Lainey is a first year Nutrition Communication student and registered dietitian.  She loves drinking coffee and hopes to help people have a positive relationship with food (and drinks).  In addition, she has fun working at her jewelry business Stella and Dot and blogging at http://bitebybitestepbystep.wordpress.com/

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