What Exactly Are Net Carbs? Here’s What You Need to Know
You may have seen "net carbs" on food labels, but what are net carbs—and should you pay attention to them? Here's everything you need to know, including how to calculate net carbs and what they mean.
Yes, eating carbs are good for you. Complex carbohydrates provide fibre and key nutrients that are important for a well-rounded diet. They are the body’s main source of energy, and include some of the healthiest foods you can eat.
But there are many people who swear by eating a low-carb diet or those who practice carb-cycling where you change your intake from low carb to moderate to high carb day to day, week to week, or monthly
A controversial topic amongst low-carb dieters is whether or not to track or count net carbs. To understand net carbs, however, it’s important to first know the basics about carbohydrates in general.
(Related: 14 Low-Carb Diet Mistakes to Avoid)
What is a carbohydrate?
Carbohydrates are the body’s preferred source of energy. While it’s true that the body can use protein and fat to make energy, these two macronutrients also serve other purposes for the body which carbs cannot.
For example, the body uses protein to build muscle tissue, and protein also makes up enzymes. Fat is utilized for cell growth, to produce certain hormones, and is the body’s main form of energy storage. By eating carbohydrates, we spare protein and fat so that they may be used for their primary purpose.
However, when carbohydrate intake is low, our bodies convert fat and protein to be used for energy production. If the total intake of food is too low to support energy needs, the body converts stored carbohydrates, called glycogen, and stored fat and muscle, for energy use.
Types of carbohydrates
Carbohydrates fall into three categories: starches, sugar, and fibre. Starches are the main form of energy storage for plants and the body utilizes them for energy.
Dietary fibre comes from fruits, vegetables, and grains but can’t be fully digested by the human body (although it has a ton of health benefits). As for sugar, there are naturally occurring sugars in fruit and milk, as well as added sugar found in processed foods.
Carbohydrates can also be simple or complex. Simple carbohydrates are easily absorbed by the body and tend to taste sweeter than their complex counterparts. Fruit, for example, contains a lot of simple carbohydrates, giving rise to their sweet taste. Honey and table sugar are also simple carbohydrates but lack the fibre that comes with fruit.
Complex carbohydrates, on the other hand, tend to have more fibre and can be found in potatoes, rice, wheat, squash, and beans.
(Related: 10 Foods with More Fibre Than Broccoli)
What are net carbs and how do you calculate them?
Net carbs are the actual amount of carbohydrates that your body digests and absorbs from food. However, they are somewhat controversial.
Net carbs are not listed on the Nutrition Facts label. Some manufacturers list net carbs somewhere else on the label although they may refer to them as impact or digestible carbs.
You can calculate the net carbs by taking the total carbohydrates listed on a food label and subtracting the fibre and sugar alcohols. (In whole foods, you would calculate the net carbs by subtracting the fibre from the total carbohydrates.)
Sugar alcohols are carbohydrates that are used as sweeteners because they have fewer calories—about half—compared with regular sugar. Some common names of sugar alcohols are xylitol, mannitol, and sorbitol. (You often find them listed in sugar-free gums or candy, and they can cause diarrhea when consumed in large quantities.)
Unlike other types of carbs, fibre doesn’t raise your blood sugar much at all—in fact, it slows down the rate of glucose entering the bloodstream. If we eat a food that contains a low amount of fibre, that food will be broken down and absorbed much more quickly than a high fibre food, leading to a spike in blood glucose.
By subtracting these two types of carbs, net carbs promise to more accurately pinpoint a food’s true impact on your blood sugar.
(Related: Why Low-Carb Diets Aren’t the Answer)
Why do people count net carbs?
People on low carbohydrate diets such as the Atkins diet or the ketogenic diet may use net carbs so that they can consume more carb-containing foods on these strictly regulated diets.
People with diabetes or prediabetes are advised to keep track of total carbohydrates to help determine how the foods they eat will affect the body, and specifically, their blood sugar level. (Or if they are on insulin, they may need to calculate an insulin dose to match their carb intake.)
There is no official equation for calculating net carbs because there are so many variables and their precise effect on blood glucose is not considered to be accurate. For example, nutrition labels do not give the exact types of fibre and sugar alcohols present, so a net carbs number may suggest a food has a lower impact on blood sugar than it actually does.
It’s true that only about half of the carbohydrate grams from sugar alcohols and about half or less from dietary fibre are metabolized to glucose. In contrast, almost all other carbohydrates becomes blood glucose, according to the Journal of the American Dietetic Association.
However, how the body processes them varies widely. One study in Nutrition Research Reviews found that the small intestine absorbs anywhere from 2–90 percent of sugar alcohols. However, some are only briefly absorbed into the bloodstream and then excreted in the urine.
If you’re counting net carbs, you may be overly obsessed with your fibre intake, which we know Canadians don’t get enough of. Fibre helps maintain a healthy weight because of how slowly it is digested and also aids gut health. So more fibre is always a win in my book.
Personally, I don’t think there is any reason to count net carbs for the reasons mentioned above: It’s not standardized, and too many variables can skew the numbers.
Eating a varied diet with plenty of fibre is the aim for the majority of us, which is why I advise my clients to aim for between 25-30 grams per day and make sure they also get plenty of water simultaneously. This combination will help with weight management and good gut function, which are good goals.