Today’s population has become increasingly infatuated with carbohydrates and how best to avoid them in daily diets. In fact, the low-carb industry has grown exponentially, with no signs of slowing down anytime soon. With all this talk about no-carb, low-carb and now, net carbs, it's easy to get confused or overwhelmed.
The term "net carb" is gaining steam as consumers become more interested in tracking their macronutrients. But before you can understand a net carb, it is important to understand how carbohydrates are digested in the first place.
How carbohydrates and fiber are metabolized
The digestive route for all carbohydrates is relatively the same. Whether consuming a candy bar or bagel, the body’s system begins mechanical breakdown in the mouth, as saliva is secreted. In addition to saliva, an enzyme known as amylase, breaks down the sugars of the carbohydrate.
As food continues through the digestive system, it is broken down further into glucose by the liver, and stored in the form of glycogen in your muscles and cells. Body systems will then utilize this stored energy to achieve its everyday functions.
Numerous structures and functions of carbohydrates control the daily work of the human body. Not all carbs are the same, and therefore, should not be treated as such. There are even carbohydrates that the human body cannot digest, for example, fiber. Similarly, sugar alcohol carbohydrates, are digested relatively untouched and without the need for insulin.
What are net carbs?
A net-carb calculation is one that takes the total absorbed carbohydrate in a food and subtracts what amount is not absorbed, like fiber and sugar alcohols.
Net carbs are also referred to as active or impact carbohydrates, that are utilized to show you how many carbohydrates you are actually digesting. This may seem simple, but as many things go in nutrition, it’s not as clear cut as it sounds.
For starters, the Food & Drug Administration has not weighed in on an official definition of net carbs. There are a few things to consider when examining the net-carb approach. The first is that not every individual metabolizes carbohydrates in the same manner. In fact, studies show that your gut bacteria may play a role in carbohydrate metabolism. Gut bacteria are like a fingerprint — everyone’s is different. Another point of contention is that the calculation can become more complex with the addition of multiple fibers and sugar alcohols in a product.
Factors impacting digestibility of carbohydrates
Fiber can safely be said to have no impact on insulin and blood sugar in the body. It is a non-digestible component of complex carbohydrates, lowering the total amount of carbohydrates digested. For example, a bean-based pasta has 20 grams of carbohydrates per serving and 12 grams of fiber. Since the fiber is not broken down, it is deducted from the 20 grams of carbohydrates. In theory, consumption of this product limits your net carbs to only 8 grams.
Sugar alcohols are carbohydrates that are found naturally in some foods, but the majority of them are now seen in low-carb food products. They are only partially digested, but their glycemic index (the measure of impact to blood sugar and insulin) relies on the type. Sorbitol and xylitol are slightly higher on the index than erythritol which has a glycemic index of zero. To put this in perspective, the glycemic index of table sugar is about 65.
Should you use net-carb calculations in a low-carb approach?
I like a net-carb approach with my low-carb patients because it forces them to become more conscious about their choices. For example, if I give my patient a 50-gram carbohydrate limit for the day, they will surely choose the bean-based pasta over the basic whole-grain pasta, as it provides a minimal amount of digestible carbohydrate. A whole-wheat option could pass on at least 20 more carbs to their daily limit.
A net-carb approach is not an exact science by any means, but at least it causes my patients to focus on fiber and avoid sugar. Just realize that the calculation in whole foods, an apple for example, will most likely be more exact than in a food product.
A net-carb approach is gaining popularity and knowing how the calculation is made can provide you the insight and power you need to truly alter your diet.