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Diabetes Diet - What are Net Carbs?

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What are Net Carbs?

By Nina Nazor

Carb Counting and Food Labels

With the low-carb craze the food industry has come up with a new category of carbohydrates known as "net carbs", which are believed to have none or little impact on blood glucose levels. Lets see what is true and what fiction about them.

Types of carbohydrates

Carbs are found in three basic forms:

  1. Monosaccharides: They have one sugar unit. For example glucose or fructose
  2. Disaccharides: These have two sugar units bonded together. For example, sucrose or table sugar, which consists of a glucose unit bonded to a fructose unit
  3. Polysaccharides: These are formed of long chains of simple sugar units bonded together. For example:
  • Starch, a polymer of glucose, is the principal polysaccharide that plants use to store glucose for later use as energy.
  • Glycogen is the natural polysaccaride that our bodies use to store glucose for later use.
  • Cellulose, also known as fiber, which gives plants their rigidity and can’t be digested by humans. Therefore, it is not absorbed into the body.

Monosaccharides and dissaccharides are also known as simple carbohydrates, which are absorbed rapidly and have a high glycemic index. Polysaccharides are also known as complex carbohydrates, they are absorbed more slowly and usually have a lower glycemic index.

The carb content of processed foods usually includes sugars, starches, fiber, sugar alcohols, polydextrose, and other organic compounds.

What are “net carbs”?

The term “net carbs” refers to the total number of carbohydrates minus fiber, glycerin and sugar alcohols. In other words, net carbs are the total amount of carbs in food that can be absorbed and digested in the intestinal tract.

The general belief is that fiber, glycerin and sugar alcohols don't raise blood glucose levels. But in reality, glycerin and some sugar alcohols can affect blood glucose.

When you read the Nutrition Facts label of a product that claims to have “net carbs”, the manufacturer might have taken the total number of carbohydrates the product contains, and subtract fiber and sugar alcohols to obtain the amount of “net carbs.”

What are sugar alcohols?

Sugar alcohols are carbohydrates that we don’t absorb completely. They are naturally present in small amounts in fruits and vegetables and are very similar chemically to sugar.

Sugar alcohols are commonly used as artificial sweeteners and are made by adding hydrogen atoms to sugars. For example, if you add hydrogen to glucose the result is sorbitol. The most commonly used in foods are mannitol, sorbitol, xylitol, lactitol, isomalt, maltitol, and hydrogenated starch hydrolysates.

Do sugar alcohols provide calories?

Some do and some don't. Some sugar alcohols are absorbed better than others and that makes them affect blood glucose levels differently. For example, maltitol and hydrogenated starch hydrolysates, are absorbed enough to provide almost 75% of the calories of sugar.

What is the glycemic index of sugar alcohols?

Some sugar alcohols have a higher glycemic index than others. Take a look at their glycemic index in the following table, as well as the amount of calories they provide. Remember that glucose has a glycemic index of 100.

What are Glycerin and Polydextrose?

Glycerin is not a carbohydrate, but provides 4.32 calories per gram. It is classified as a sugar alcohol and is widely used in processed foods as an additive and sweetener. Recent research has shown that glycerin only raises blood glucose levels a little bit.

Polydextrose is a food additive derived from glucose. It has a low digestible energy value; it is used as bulking agent in foods to reduce the caloric content.

Is it safe to use these substances?

It is generally considered that the use of sugar alcohols, glicerine and/or polydextrose in foods is safe. However, in the case of sugar alcohols, if you eat them in large amounts, usually from 20 to 50 grams, they can cause you bloating, gas and/or diarrhea.

What is the conclusion?

Read the Nutrition Facts Label of the diet and low carb products you buy to know the amount and type of carbs they contain. Fiber, glycerin and polydextrose practically do not affect blood glucose levels. Sugar alcohols do affect blood glucose levels. Maltitol and its syrups tend to have a greater effect on glucose levels; erythritol and mannitol have no effect at all on glucose levels, while xylitol, isomalt, sorbitol and lactitol have some effect.

Source: Livesey, G. Health potential of polyols as sugar replacers, with emphasis on low glycemic properties. Nutrition Research Reviews 2003;16:163-91.