We’ve all seen it on food labels: “Only 2 net carbs” or “Low net carbs.” But what does this truly mean? What are net carbs, and why does it matter? Are all net carbs created equal, or are we stretching those claims a bit too much? After reading through this article, I think you will agree that there is a pressing need to educate on the precise definition of net carbs, and what exactly constitutes a true fiber.
To figure out the correct amount of fiber for your body, try experimenting. If you’re on the keto diet, start with 15-20 grams of total dietary fiber per day from a mix of soluble and insoluble fiber for several weeks, then consider adding 3-5 grams at a time as needed to see how you feel. Remember that some people actually feel worse when they boost their fiber intake[*][*][*].
A close relative of maltose is a molecule known as isomaltose (typically found in items such as beer and honey). The biggest difference between maltose and isomaltose is that isomaltose is joined together by an α-1,6 chemical bond, rather than an α-1,4 chemical bond. Scientists suspected that by adding a certain enzyme (transglucosidase) to high maltose syrup, they could change the bonds from α-1,4 to α-1,6, thereby making it more resistant to being broken down by the enzymes, as described above, when compared to maltose. Again, while this sounds excellent in theory, it is not necessarily what happens in our bodies. In fact, isomaltose (and thus, IMO syrups used in some of these products) is broken down by certain enzymes on the brush border of the small intestine. Though the α-1,6 bond breaks down slower compared to the α-1,4 bond, these IMO syrups, which often use a blend of di-and oligosaccharides, ultimately metabolize into small amounts of glucose and maltose and thus should be viewed as a slow digesting carbohydrate rather than a true fiber.
Breath Hydrogen is an assay that indicates in “real-time” whether or not a particular nutrient is being digested. Upon consumption of a standard carbohydrate (e.g., rice), you can see that it is broken down in the small intestine, and, subsequently, blood glucose rises. If the carbohydrate is not digested in the small intestine, it moves into the large intestine. This indicates that it is a “true fiber.” In the large intestine, bacteria digest the fiber through a process called “fermentation.” In doing so, the bacteria produce hydrogen ions (H+) that circulate into the bloodstream, through our lungs, and is then exhaled outward. We monitored a subject consuming either IMOs or SCF respectively and then tracked the variables listed above for 150 minutes following consumption.
Taken together, previous research in combination with our lab’s current research may argue that IMOs should not be classified as a “true fiber.” Rather, IMOs should be viewed as a very low glycemic carbohydrate source, much like steel cut oats. In essence, if you see a low-carb snack that has 20 grams of IMO fiber, it is likely that approximately 16 grams of this fiber will act as a slow-digesting carb, and four grams will act as an indigestible fiber. Those who are on a ketogenic diet should be aware of these fibers and proceed with caution when consuming them in large amounts, as they could raise both blood glucose and insulin levels. A more ketogenic-friendly fiber is SCF, which has been demonstrated to act as more of a true fiber. Additionally, SCF is very tolerable in the gut despite its profound prebiotic activity. It is important to keep in mind that everyone is metabolically different, so if you are consuming food items with these fibers in them, be sure to monitor blood glucose and ketone readings to find how each of these fibers personally affects you.
Thus far, we have established what IMO is and how its structure can differ in regard to its carbon bonds. The real question is, “What are the metabolic responses of products that contain these IMOs?” The glycemic index of IMO is very low, however, it has been shown to be nearly completely digested (83 % or more) by enzymes on the small intestinal border. Thus, IMOs should not necessarily be classified as a true fiber but rather as a low glycemic carbohydrate like steel cut oatmeal, at about 3.3 calories per gram.
If you are aware of what you’re eating throughout the day, you can better plan for indulgences. When traveling to a place that is known for their cuisine, enjoy eating while remaining balanced about your diet. Instead of getting a sweet all to yourself, maybe share it with whoever you are going. By sampling small portions of food, instead of overeating till you feel sick, you can enjoy your vacation food while still keeping your Keto Diet in mind. Alternatively, be sure to get as much exercise as possible (walk to destinations instead of taking a bus or driving), and the extra exertion will help use up any extra calories (or carbs) that you may eat.
The increased awareness regarding the importance of fiber, in addition to its distinct metabolic effects, has resulted in a surge of companies switching to an alternative fiber known as soluble corn fiber (SCF). Interestingly, SCF has been available on the US market since 2007 and is used in foods and beverages across the Americas, Europe, and Southeast Asia. SCF is produced through an extensive process: corn syrup is exposed to a suite of enzymes for at least 48 hours, some of which are found in the brush border of your small intestine, as well as the pancreas. Notably, a large majority of the corn syrup contains easily digestible carbohydrates; however, a small portion is, in fact, not digestible. At the end of this enzymatic exposure, a stream of digestion-resistant carbohydrates remains and is subsequently filtered several times. The resulting product is a “true fiber” that contains a mixture of α-1,6, α-1,4, α-1,2, and α-1,3 glucosidic linkages, which, as mentioned above, contribute to its low digestibility.