Debbie writes:
“Can you talk about the concept of “net carbs”? I see this listed on the front of the package for some foods. It seems to be the total carbs minus the fiber. Is there any benefit to thinking of carbs this way? It seems it could be confusing to Type 1 diabetics who are instructed to dose their insulin based on total meal carbs.”
What Are Net Carbs?
The first thing you need to know about net carbs (also known as “effective carbs” or “impact carbs”) is that these are completely unregulated terms. There are no established or enforced standards for how this number is calculated.
Although U.S. regulators have allowed these terms to be used on the front of packages (but not on Nutrition Facts labels), the Canadian authorities have prohibited manufacturers from including these terms anywhere on their package labeling, on the grounds that there is no scientific consensus on their definition and they might be used to mislead consumers.
How Are Net Carbs Calculated?
Net carbs are typically calculated by subtracting fiber and sugar alcohols from the amount of total carbs. The idea here is to distinguish between sugar and starches—carbohydrates which have about 4 calories per gram and cause your blood sugar to rise—and other types of carbohydrates which are much lower in calories and have less of an impact on your blood sugar.
See Also: What Is High Glucose?
Fiber, of course, is found in whole grains, fruits, vegetables, legumes, nuts and seeds. Although fiber is technically a carbohydrate, the human digestive system isn’t able to break it down to release any energy or calories. Fiber passes largely undigested through our systems, although it does provide a food source for the beneficial bacteria that live in our intestines and has other benefits as well.
See also: What is the Difference Between Soluble and Insoluble Fiber?
Sugar alcohols taste sweet but because the shape of the molecule is slightly different than a true sugar, sugar alcohols do not cause an increase in blood sugar. They are lower in calories than sugar but not calorie-free.
See also: What Are Sugar Alcohols?
Why Do Net Carbs Matter?
The net carb phenomenon grew out of the low carb dieting craze, where people attempt to reduce their consumption of carbohydrates to just 20 or 30 grams per day, or about 1/10th the amount of carbohydrates that a more typical diet contains. As you might imagine, this can be quite challenging.
But because fiber is largely indigestible, low-carb dieters reason that it shouldn't count toward their carb count. And because sugar alcohols are not actually sugars and aren’t absorbed into the bloodstream the way regular sugar are, these too were exempted.
Food manufacturers jumped on board the low carb bandwagon in a big way, creating all kinds of bars, shakes, and other processed foods for low-carb dieters and using net carbs as a marketing device. A low-carb snack bar might contain 20 grams of total carbs, but if 10 of those grams were fiber and 8 of those grams were sugar alcohols, they could promote that bar as having only 2 grams of “net carbs.”
Can You Lose Weight By Counting Net Carbs?
If you’re trying to lose weight, it might seem that foods that are advertised as being low in net carbs would be a great choice. A Milky Way candy bar, for example, has 41 grams of carbs. An Atkins bar, on the other hand, which is sweetened with sugar alcohols, has 23 grams of total carbs but just 3 grams of net carbs. You could have 13 Atkins bars and have consumed fewer net carbohydrates than you get in a single Milky Way!
Low carb does not mean low calorie, however. In fact, an Atkins bar and a Milky Way have the same number of calories. If all you’re paying attention to is net carbs, you could end up eating a lot more calories than you realize.
Are Net Carbs Useful for Diabetics?
But what about insulin dependent diabetics? As Debbie mentioned, diabetics who require insulin to regulate their blood sugar are taught to calculate their insulin doses based on the total amount of carbohydrates in a meal. But should they count an Atkins bar as 23 grams of carbs or as 3 grams of net carbs?
Sugar alcohols have less of an effect on blood sugar but they don’t have zero effect.
Neither. Although calculating insulin needs based on total carbs works pretty well for whole foods, it’s not as reliable when dealing with highly processed foods where the ratio of digestible and indigestible carbohydrates has been drastically manipulated. Basing insulin doses on the total carbs in this type of food could result in blood sugar levels dipping too low. But basing your insulin amount on the net carbs could result in too low a dose.
Sugar alcohols have less of an effect on blood sugar but they don’t have zero effect. In large amounts, they can raise your blood sugar levels. Bottom line: diabetics should tread carefully with foods where there is a double digit difference between total and net carbs.
The Bottom Line on Net Carbs
Although whole foods that are naturally high in fiber and/or low in sugar could be described as being low in net carbs, I have yet to see a Jerusalem artichoke or bunch of collard greens with a net carb label attached. The foods that are touting their “net carb” credentials are usually highly processed foods. Although a high-fiber, low-sugar “candy bar” might be preferable (nutritionally, anyway) to one that’s low in fiber and higher in sugar, neither one should be a major part of your diet.
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