Whether you’re someone who indulges in Guinness only on St. Patrick’s Day, or you enjoy a pint on the reg, it’s fair to say that the stout is Ireland’s most internationally famous beer. Though darkly colored, Guinness is surprisingly light, and lower in alcohol and sugars than a lot of other beers.

But one thing the stout apparently hasn’t been all this time is vegan. That’s right, for over 250 years, Guinness has used fish bladders in its brewing process. But why?

Well, there’s actually a valid reason. A by-product of the bladders known as isinglass helps settle yeast quicker during the fermentation process, which ultimately clarifies the beer. Though it’s filtered out, there are still trace amounts that wind up in the beer you drink. The reason you may not have known you were drinking fish bladders is that Guinness and other brewers weren’t required to list it on their bottles and cans.


But vegan and vegetarian fans of the beer have been pestering Guinness to stop using isinglass for years now, and Guinness has finally listened. The brewery plans on using a new filtration process that will eliminate the need for isinglass, which will be implemented by 2016.

So, if you actually like fish bladders in your beer, you better stock up on Guinness while you have the chance.

[via The Independent]