You may have heard about “net carbs,” but what exactly is the meaning and significance behind them? The concept of net carbs became popular with the emergence of keto and the Atkins Diet, which instructed individuals to calculate net carbs by subtracting fiber and sugar alcohols from the “total carbohydrates” amount on the Nutrition Facts panel.
The theory behind this is that fiber and sugar alcohols do not significantly affect blood sugar and therefore don’t “count” like other sources of carbs. Although this may seem like a sound theory to some, it is not entirely accurate. In order to fully understand the relevance of the net carb concept, it is important to first understand the functions of carbohydrates, fiber and sugar alcohols.
WHAT ARE CARBOHYDRATES?
All macronutrients (think: protein, fat, carbohydrates) give the body energy to fuel it through all sorts of activity, from a serene nap to a heart-pounding mile run. While protein and fat aid in a variety of processes such as cell structure, function and maintenance, the main role of carbs is to provide the body with fuel. Carbs are more readily broken down compared with fats and protein.
All carbs are converted into glucose (a sugar) during digestion and then flood the bloodstream. Your body then has to decide to use glucose for energy or store it as glycogen (a starch) or fat. Since you have a limited capacity to store glucose as glycogen, much of the unused glucose will likely be stored as fat. Since insulin helps your body use and store glucose, it’s believed that if you can keep insulin levels low, it will help your body burn fat instead of storing it. This is the theory behind monitoring blood sugar levels for weight management purposes, but it is difficult to determine the blood sugar levels that will lead to fat storage because everyone’s carbohydrate needs are unique.
How fast you process carbohydrates depends on the type of carbohydrates you’re eating. The more simple in nature a carbohydrate is, the quicker it is metabolized. Simple sugars (think: candy, syrup or soda) are digested really quickly so they rapidly spike your blood sugar. In contrast, vegetables and whole grains contain fiber, a type of carbohydrate that is harder to digest. As a result, they won’t spike blood sugar and insulin quite as quickly or sharply. The concept of “net carbs” focuses attention on carbs that increase blood sugar and insulin more quickly.
Fiber is a type of carb that isn’t fully broken down during digestion and therefore does not provide energy (or calories). This means that it has little to no impact on blood sugar levels and why it is subtracted from the total grams of carbs.
There are two types of fiber that have different roles.
- Insoluble fiber is not absorbed or broken down by the body, and it aids in removing waste from the intestinal tract while providing bulk and softness to stools to prevent constipation.
- Soluble fiber is also not absorbed by the body, but it dissolves to become a gummy substance that helps to regulate blood sugar by slowing the absorption of glucose. It is also responsible for helping to lower cholesterol.
The American Heart Association recommends that adults consume 25–30 grams of total fiber per day as way to promote overall wellness and a healthy heart. Good sources of fiber include whole grains, fruits, vegetables, beans, nuts and seeds.
Don’t just trust a “net carb” label on a food. Make sure you read the ingredients list to see how many grams of fiber that food contains.
SUGAR ALCOHOLS
Ever wonder how your local grocery store can carry “sugar-free” candies? Chances are these products contain sugar alcohol to provide the sweetness of sugar with fewer calories. There are many different types of sugar alcohols, and they each affect the body differently. Many of these sugar alcohols have been studied in research but not extensively. The available research even suggests that they have unpredictable effects on blood sugar, and it’s generally considered that they do raise blood sugar.
The issue with the net carbs concept is that sugar alcohols are generalized into one category when they are all very different. To know which sugar alcohols are in a food or beverage, you can check the ingredients listed on the packaging. The following are common sugar alcohols used in food and beverage production:
- Xylitol
- Sorbitol
- Mannitol
- Maltitol
- Lactitol
- Erythritol
- Glycerol
- Isomalt
- Hydrogenated starch hydrolysates
By the way, eating too much sugar alcohols (more than 10 grams per day) isn’t recommended since they can cause tummy issues.
There isn’t a legal definition of “net carbs,” and the Food and Drug Administration does not recognize claims that involve net carbs as legitimate. In theory, net carbs are the amount of carbs from your food that can affect your blood sugar levels. Since we already discussed that sugar alcohols could impact blood sugar levels, it doesn’t seem like net carbs is the most reliable approach for managing carbohydrate intake.
When you see a net carb claim on a food label, this is just a marketing technique. This claim does not hold significant value in most cases. It is important to evaluate the Nutrition Facts panel for the total carbohydrate content as well as the other nutrient content such as total calories, protein, fiber and fat.
Individuals living with diabetes are often advised to subtract fiber from their foods’ total carbs in order to determine the amount of carbs that their body will absorb. This is important for them to know because their bodies have difficulty absorbing glucose. The American Diabetes Association also advises individuals with diabetes to count half the amount of sugar alcohols as carbs. For example, a sugar-free snack with 6 grams of sugar alcohols would count as 3 grams of carbs.
For the general population, I encourage people to simply focus on including more naturally high-fiber foods to achieve the recommended 25+ grams a day, as we are certain a high-fiber diet is connected to overall better health and weight. High-fiber foods will have a lower impact on blood sugar levels and will also help keep you fuller and more satisfied longer after meals.
Stick to your low-carb goals by tracking total net carbs in each food, meal and day in the MyFitnessPal app.
