Vitamin Water Zero - how can this be?

I was looking for new flavors of water today and picked up a bottle of Vitamin Water Zero.

0 calories
4g. carbs, Ig. sugar

How can it be 0 calories with 4 carbs ? By my calculation it should have 16 calories. Am I totally math impaired or is there some magic to this water?

I think it has to do with the fruit juice, but I'm not sure.  I have steered clear of vitamin waters for that very reason.  I know there are some Sobe Life waters that are all 0, and my husband and I tend to drink a lot of Powerade Zero, they are 0 carb/cal

sugar alcohols count as a carb, though they are very low calorie. If you see sorbitol, xylitol, malitol, etc, then the carbs are from sugar alcohols. And, zero water can be labeled zero calorie if there is some tiny amount of calories per serving, and usually there are two or three servings pet bottle. If it gets you your water, I say go for it.

The FDA allows manufacturers to label things as "zero" when they have a minimal amount of calories.  You'll notice the Vitamin Water Zero number of servings is 2 1/2.  So, each serving has a minimal amount of calories.  If I remember right, the entire bottle really has 40 or 45 calories.  Damn the FDA!

Google to the rescue... The FDA tolerance is 5 calories per serving, so there are probably 12 or 13 calories in the 2'5 serving bottle. The sugar alcohols like erythritol have like .2 or.4 calories per gram instead of sugar's 4. How confusing labels can be!

I'm a biochemist - perhaps I can help.  (I love saying that in a crowded elevator).

It's an artifact of FDA nutritional labeling law.

Vitamin water is sweetened with sugar alcohols.  Not "real" sugar - artificial sweetener.

A serving has 4 g of artificial sweeter, like it says on the label.

One gram of sugar is 4 calories.  But one gram of sugar alcohols isn't 4 calories.  Depending on the sweetener, it may be a fraction of a calorie.

This is really confusing for people like you, who are paying attention.  4 grams of sugar alcohol may add up to 2 or 3 calories, and companies are allowed to round down to the nearest value, so they could report zero.

This isn't the only problem with the way FDA treats carbohydrate labeling - they also include fiber count under carbohydrates (since technically and biochemically they are carbohydrates) but you'll notice that fiber (because you don't break it down and digest it) does not add to the calorie content of food either.  In my opinion, it would be easier on consumer understanding to separate out fiber from carb count - you don't want people wanting to "low carb" to pass on good fiber sources.