“Mystery Carbs” Question of the Day

We like to think we’ve got a handle on this carb-counting thing. But the truth is, most of us have very little clue — not least because nutrition labels on packaged products are so darn confusing. One of our beta testers over at the new community recently posted this query:

Nutrition_wheel When I’m counting carbs I often read the “category” of carbs that are in the food I’m eating (i.e. Dietary Fiber, Sugar, Other Carbohydrates, etc.). I have noticed that often they don’t quite add up to the Total Carbohydrate amount.

Maybe this is a stupid question with an obvious answer but:

Does anyone know what these “mystery carbs” are or where they come from?

Not a stupid question at all. I couldn’t answer it off-hand. Why are we consuming more carbs than appears necessary or possible based on the corresponding food data? For some insight, I turned to local San Francisco nutrition expert Norae Ferrara. Of course, nothing is simple with diabetes. The answer was much more than I bargained for. Here’s what this food whiz had to say:

Label reading can be tricky because the original purpose which is to provide accurate, useful, information is also clouded by marketing strategies of most companies who may add more information than is required, or practice “rounding” of values to emphasize or de-emphasize certain components.
To further explain:
Definition of Carbohydrates
Carbohydrates are made up of: 1) Complex Carbohydrates, 2) Simple sugars (or sugar), and 3) Dietary fiber (sometimes separated into soluble and insoluble on the label)
Required Labeling of Carbohydrates in the US:
United States Federal Law requires that companies state on the nutrition facts label the total grams of carbohydrates, dietary fiber, and sugars. This makes listing the content of complex carbohydrates as optional, which in most cases, will make up for the difference between total carbohydrate, and the sum of dietary fiber and sugars.
A truly complete label for a breakfast cereal might look like this (remember, each time a component is listed as a subgroup–underneath and indented to the right–it means that it is included in the total listed above):
Total Carbohydrate 24g
Dietary Fiber 3g
Soluble Fiber 1g
Insoluble Fiber 2g
Sugars 10g
Other Carbohydrate 11g
While the more common food label will list only what is required, for example the same product might also be listed as:
Total Carbohydrate 24g
Dietary Fiber 3g
Sugars 10g
Companies may choose to round up or down to the nearest .5g. They may choose to round .3g fiber up to .5g, or just call it “less than 1g”, when it is a desired component, or they may choose to round .3g sugar to 0g, for example, when the component is not highly desirable.

That sounds pretty sneaky to me. Might be OK for enticing dieters to eat their products, but a veritable nightmare for anyone attempting to dose insulin based on that information. No wonder I manage to make frequent “mistakes” even when I’m eating neatly labeled foods. I know what you’re thinking: don’t trust the packaging, learn to estimate carbs yourself — within a fraction of .5g. Correct. Great strategy. But it seems like that could take a lifetime, and a lot patience that I do not possess. *Sigh*


13 Responses

  1. Laura Williams
    Laura Williams May 2, 2008 at 7:22 am | | Reply

    I’ve always wondered why the numbers on nutritional labels don’t add up. Thanks for the clarification.

  2. Brendan
    Brendan May 2, 2008 at 7:35 am | | Reply

    I’ve also heard that carbs on the label are the resulting value from taking the total weight of the food item and subtracting fats and proteins. What’s left is called carbs since they are harder to measure than the other two.

  3. Sean
    Sean May 2, 2008 at 8:05 am | | Reply

    I asked a similar question of my CDE and got a number of reasons for the mystery carbs indicated by a high BG after eating and dosing but none of those reasons were that the nutritional labels were incorrect, though, now I know they can be. She suggested that I try a variable carb ratio based on time of day or that it could be the timing of long acting insulin

  4. tmana
    tmana May 2, 2008 at 8:37 am | | Reply

    The USDA Nutrient Data Laboratory’s “National Nutrient Database for Standard Reference — Release 20″, MS Access database (downloadable from http://www.ars.usda.gov/main/site_main.htm?modecode=12354500 ), notes in its NUTR_DEF table that carbohydrates are measured “by difference”. The table even provides for breakdown by several specific mono- and disaccharides, but this information is not available for more than 80% of the foods in the 7500-food database. (approximately 7500 foods and I can rarely find the one I’m looking for — that database is by no means complete!)
    Draw from that (1) confirmation of what Brendan “heard”, and (2) that the government either does not have, or refuses to publish, complete nutritional data on even the small number of foods in its database.
    You may also draw from that the ability to manipulate what information *is* provided by our tax dollars to your personal advantage.

  5. elizabeth joy
    elizabeth joy May 2, 2008 at 8:46 am | | Reply

    Okay, you think that’s bad? You ever dose based on a packaged carb count and find your sugar running way low or way high for no discernable reason? Get this.

    The FDA allows up to a 20% increase in the listed amounts on nutrition labels. Take a small bag of Doritos, they are 54g, which means a 20% increase would be nearly 65g. If you have an 11/1 carb ratio, you are a full unit short on that meal bolus. But given the individual bag, the actual amount could be anywhere between 54g and 65g.

    I think the only solution for us is to never eat again…

  6. Eric Jensen
    Eric Jensen May 2, 2008 at 12:01 pm | | Reply

    OK, I have to differ with the overall message of this post and with many of the comments here. The original question was why the total carbohydrates figure doesn’t always add up to the sum of the individual carbohydrate figures, and the answer was clearly stated – some kinds of carbs are not required to be specified *individually*. But note – they *are still included* in the total carb figure. So if you dose on the total carb figure, you’re still using what is, by and large, an accurate number. It’s not clear to me why this is “sneaky” or should lead to mistakes. Granted, you might like to know how those carbs are broken down if you’re very precise about scaling doses for different kinds of carbs (but note, fiber usually *is* specified separately). But overall, there’s nothing in that statement that indicates you’ll go far wrong using the “Total carbohydrates” figure.

    Regarding the rounding issue, rounding means that each individual number is off by 1 gram at most, and again the total number will be off by 1 gram at most.

    Regarding elizabeth’s comment about allowed variance in filling packages, the specification varies by package weight, and is at most 10% for packages under 36 g (note: then you’re only off by 3.6g of carbs for a food that 100% carbs) and scales down to 2% for larger packages: http://ts.nist.gov/WeightsAndMeasures/upload/All-H133-05-Z-2.pdf (Table 2-5 in Appendix A).

    While we might like to blame these small effects, I think our bigger challenge is just that our bodies are complicated – uncertainties in glucose testing, variations in insulin delivery, how your body reacts day to day based on illness or stress. All of these are bigger factors than food labeling, I think. We just all have to press on and do our best.

    One final thought – eating less packaged food avoids many of these issues with food labeling (and in general is likely to give you a healthier diet). Yes, I eat packaged things, too – but it’s a goal to shoot for.

    Thanks for listening,


  7. AmyT
    AmyT May 2, 2008 at 1:29 pm | | Reply

    My experience seems to show that the “total carbohydrate” count is often not particularly accurate either. The whole practice of “rounding” (which I call sneaky) makes me very distrustful of all the label data.

    Certainly there are MANY factors complicating our BG reaction to different foods, but this apparent practice of “fudging the labels” sure ain’t making it any easier.

  8. George S Alarcon
    George S Alarcon May 2, 2008 at 6:18 pm | | Reply

    The mystery of the carbs gets solved at last! Thanks for clearing up the web of confusion.

  9. Sam
    Sam May 2, 2008 at 6:20 pm | | Reply

    Great information on carbs.


  10. Lauren
    Lauren May 2, 2008 at 8:15 pm | | Reply

    I would lose my mind if I ever tried to count carbs. I guesstimate everything. My strategies are plenty of exercise and selective low-glycemic eating (I’ve just discovered vegan omelettes). The two longtime type 1s in my family thought I was crazy when I asked them about carb counting. They have been diabetic so long they go by past experience, and have eliminated certain troublesome foods from their diets (such as popcorn). I’m also learning that there are certain things I just can’t eat if I want good post-prandial sugars.

  11. mollyjade
    mollyjade May 2, 2008 at 11:34 pm | | Reply

    And this doesn’t even get into sugar alcohols or glycerin which are carbs that are only partially digested. It’s amazing that we can estimate carbs as well as we do.

  12. Anne
    Anne May 5, 2008 at 12:31 pm | | Reply

    On a related note, one might want to check the ingredients for trans fats, since if it is below a certain amount (not sure what that is, perhaps .5 g per serving?) it does not have to be listed under the “fats” category. Anything “partially hydrogenated” = trans fats. I have eliminated trans fats from my diet since it became more widely published how harmful they are. And also if you are eating more than one serving, that 0.5 could start to add up.

  13. AJ
    AJ May 7, 2008 at 1:09 pm | | Reply

    Reading your site always makes me dread the day my ratios change. I’m a fairly new PWD, and I’m 1:20 or 1:30 depending on time of day. Makes counting much easier.

    I can definitely see where the frustration would come in if it were 1:10 or something like that.

    I’d be curious to hear everyone else’s ratios, actually. If you’re willing to post them.

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