And no sweeteners? I was thinking the same thing. Only other answer I could come up with is perhaps sugar alcohols? Allot of the time they don't add calories but it's usually gross. Either that or they're rounding down. In the States, if one serving of something is under 5 calories they're allowed to round down, thus "zero calories".  For instance a sugar free red bull has 12 calories per can if you add up the nutrition into provided on the label; Yet the can states it only has 10.  I suck at explaining things today so my apologies.