Understanding Carbohydrate Counts | Low Carb Diets 101

A Reader Asks About Figuring Carb Counts

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Carb counting can be hard when starting a low carb diet. Here we explain the three most important issues involving nutritional information and carb counts. Learn how to read food labels, including how a food's carb counts may vary. 

In some instances the carb counts listed in recipes may be hard to understand when compared to what's listed on the nutritional label. For example, in the recipe for Basic Flax Meal Focaccia Bread, the  package of flax seed meal says there are 5 grams of carbohydrate per 2 tablespoon serving.

The recipe calls for 2 cups of the flax seed meal. While the recipe yields 0.8 grams of carbohydrate in each serving of the 12 servings the recipe calls for. This number differs greatly from what's on the label. 

There are three important issues that explain that the carb counts listed in all nutritional information:

Fiber and Effective Carbohydrate

Fiber is a carbohydrate, but since it isn’t digested, most low carb diets say it doesn’t “count” in the total carbohydrate you eat. The reason it doesn't count is because it won’t impact blood glucose (except perhaps in a positive way by slowing the impact of the other carbs ingested). Whenever I give nutritional information at the end of a recipe, I cover this issue by saying how much effective carbohydrate (that is, total minus fiber) in a serving and then I give the fiber count. So in the case of the focaccia, I say that there is a .8 gram *effective* carbohydrate plus 5 grams of fiber in a serving.

Again, while this fiber is carbohydrate, it provides no calories or "useable" carbs.

NOTE: The package says that each 2 tablespoon serving has 4 grams of fiber, which makes the effective carb count 1 gram per serving. But sometimes packages vary.

Nutritional Information is Just an Estimate

All nutritional information is just an estimate.

Every food varies in composition from one to another and individual packages may have varying nutritional value, but the label will likely be the same across the same products. The particular variety of plant or animal, where it grew, the weather, the fertilizer – many factors go into the final product. Ask a wine aficionado about this, and they will tell you how true this is for grapes, to the point where the flavor varies based on where the grapes grew. It is just as true for every other fresh food and the products made from it. So, we can never know exactly how many carbs or calories or vitamins are in any particular strawberry, unless we analyze that particular strawberry. Since nutritional labels are derived from a certain batch of food, they will reflect this variation. The USDA database (as well as the Canadian and other databases) takes averages from many batches of the food to come up with their numbers. Sometimes, as they get more data, the numbers change somewhat. This happened in the most recent update of the database (version 18) which shows different carb counts for flax seed than version 17 did.

This explains some of the variation in current online databases of nutritional information.

The Serving Size on the Label 

There are no standard serving sizes for certain products. This makes figuring out carb a two-step process. Not only do you have to check the carb counts on the label, but you have to figure how the serving size on that product varies for similar products as it can have a big effect, especially if the amount used is much more than a serving size. The problem is that rounding error is multiplied. So, for example, if a label says that 1 tablespoon of a food has one gram of carbohydrate, that could be anything from .51 grams to 1.49 grams. That’s not a big deal if you are eating one serving. But there are 16 tablespoons in a cup, so the error could be as much as 8 grams in either direction if you are using that much in a recipe.

Bottom Line

It will take time and diligence, but once you get carb counts down it will come naturally. You'll know and understand how fiber, serving size and the estimation of nutritional information affects your carb counts. , By using the same products regularly and being sure you use the same serving size in recipes, you can make things a little easier to figure out.

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