What is the glycemic index of beer?

The glycemic index of beer is subject to a heated debate: The values you can find on various websites vary considerably. Before you draw rapid conclusions you have to know that there is more to that subject than you'd initially think.

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Beers contain a varying amount of rapidly digestible carbohydrates, mainly maltose. A big proportion of that maltose is converted to alcohol through fermentation. Most beers are low in carbohydrates, a glass only contains about 10 g of maltose and yes, maltose causes a rise of the blood sugar level. To understand where the conflicting data come from you have to take a closer look at the method of determining the glycemic index.

After fasting overnight the test subjects have to consume a serving of a food or beverage that contains exactly 50 g of carbohydrates in a defined time span. In the case of beer this means that the proband would have to drink about 5 beers in 15 minutes on an empty stomach. One could probably imagine that this is not an easy task and therefore the glycemic index is widely thought to be indeterminable with this method. The values you can find for beer are mostly estimations that should be handled with care. Even if beer had a GI of 110 (which is simply the value of plain maltose) as suggested by some websites, it would only have a low to moderate glycemic load due to the rather low amount of carbohydrates.

There are considerations to use a smaller serving size with only 10 g of carbohydrates to determine the GI, but it remains unclear whether the value can be extrapolated. This method found a GI of about 66 for beer. In our app Natural food guide we use this experimentally determined GI value for beer. However, some incertainties remain as it has to be considered that alcohol affects the blood sugar levels which can further falsify the GI value.

Source: C. Bamforth, Beer, Carbohydrates and Diet, J. Inst. Brew. 111(3), 259–264, 2005
Image: https://www.flickr.com/photos/quinndombrowski/5200218267 (CC BY-SA 2.0)

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