How to Calculate Net Carbs

When you start a ketogenic diet , the first thing you hear about is carbohydrates . You should reduce their consumption as much as possible and ideally consume them from low-carb fruits and vegetables. This can be understood quite easily, but a question often arises, especially when buying products that come from elsewhere: should you count total or net carbohydrates?

The difference

The total carbohydrate in a food includes the sugar in the food plus fiber , whether soluble or insoluble .

Dietary fiber is the indigestible part of plant foods and consists of two main components: insoluble fiber (cellulose and lignin, in particular) and soluble fiber (galacto-oligosaccharides and fructooligosaccharides (FOS), fermented by the intestinal microbiota [1] into short-chain fatty acids (SCFAs), acetate, propionate and butyrate).

In ketogenic diets, net carbs (i.e., available carbs that are absorbed by the body) are often counted because the belief is that dietary fiber does not affect blood sugar levels . However, this statement is correct for insoluble fiber (which the body cannot absorb and does not impact blood sugar and ketosis ), but the same cannot be said for soluble fiber.

Indeed, the human body can derive calories from soluble fiber [2]. Their effect on blood sugar , however, is not entirely clear. Studies show that soluble fiber can be absorbed and used for intestinal gluconeogenesis . This potential ability of soluble fiber to affect blood sugar and ketosis is the main reason why some experts recommend using total carbohydrates rather than net carbohydrates .

However, some studies show that soluble fiber helps lower blood sugar [3]. According to one study, propionate can be used by the body for intestinal gluconeogenesis and the overall effect of short-chain fatty acids – through intestinal gluconeogenesis – is to lower blood sugar . Unlike hepatic gluconeogenesis , intestinal gluconeogenesis helps lower serum glucose concentrations and improves glucose disposal [4] .

How to count?

The calculation is quite simple. If we want to know the net amount of carbohydrates in a food , we take the total amount and deduct the fiber .

In Europe, labels show the net carbohydrates of a product , although in some countries, such as Germany, there will also be the fiber line, but they are already deducted. On the other hand, if you buy products from the United States or Canada, the total carbohydrates as labeled include fiber ; therefore, to obtain the net carbohydrates you must deduct fiber .

Also, in sweet products that contain polyols , the total polyols are deducted from the total carbohydrate count. While this method works for the vast majority of people, it should be noted that tolerance and reaction to polyols is very individual and also depends on the type of polyol . Therefore, there will be people for whom polyols are completely harmless, and others who may have a spike in blood sugar.

Conclusion

Counting total or net carbs is a personal choice. Some people will feel better counting totals, as research is still unclear on whether soluble fiber raises or lowers blood sugar , or has no impact at all. However, the vast majority of people can count net carbs and achieve their ketogenic diet goals, due to the satiating effect of this diet and the quality of the foods you eat when you eat keto.