Low carb beer?

I was asked recently if I could brew a low carb beer. While I’m pretty
sure I could make a light beer (less alcohol) , I’m not sure about a low carb
beer. I’m an extract brewer if that matters.

Thoughts ?

With extract, about all you can do is use the lightest (and therefore most fermentable) extract you can find. You could also substitute sugar for as much as 20-30% of the fermentables. Using a highly attenuative yeast (a lager strain would be ideal if you have the capability) will also help. Essentially you want to do everything possible to reduce the FG. Most domestic light lagers, for example, finish at <1.0. You probably can’t get that low using extract.

Here’s a tool that can give you an estimate of the carbohydrates based on OG and FG: http://www.mrgoodbeer.com/carb-cal.shtml

All good advice from Sean. You can also add a little Beano to the cooled wort, that will further break down the unfermentable carbs. I’d be careful to let it go a few weeks if you’re going to bottle, because the Beano seems to take a long time to work.

I’d just go with US05 for a yeast, 20% sugar, extra light DME at an OG of 1.040. If you want a little color/flavor I’d use Victory or biscuit malt before I’d use a crystal. And if your friend liked hops it would be nice, that way you can give the stuff some more flavor since a dry beer can be kind of thin and flavorless.