There are two general categories of dietary fiber: soluble and insoluble. Fibrous foods typically contain both soluble and insoluble fibers. As a society, we understand the importance of fiber, including the benefits related to lowering body fat, decreasing the prevalence of diabetes, improving insulin sensitivity, decreasing the risk of heart disease and increasing satiety, as well as the beneficial bacteria in our digestive system. Unfortunately, less than 5% of Americans actually meet the 30 gram per day recommended intake. To help increase fiber consumption, an increasing number of companies have developed a host of delicious, low-carb, high-fiber treats. Despite this, it is important to understand how our bodies process two of the most common “fibers” on the market that are used in these treats: isomaltooligosaccharides (IMOs) and soluble corn fiber (SCF).
In contrast insoluble fiber, which does not dissolve in water, is inert to digestive enzymes in your upper gastrointestinal tract. While some forms of insoluble fiber (like resistant starch) can ferment in your colon, most insoluble fiber moves through your digestive system relatively unchanged, absorbing water as it goes, eventually adding bulk to your stool and easing your bowel movements.
As observed by the graphs above, in contrast to the IMOs in which blood glucose rapidly increased to 125 mg/dL, SCF did not elicit any blood glucose response. In addition, while insulin was elevated during the IMO condition, it actually tended to go down in the SCF condition! Despite the results from the blood glucose and insulin responses, the breath hydrogen assay will distinguish which is a “true fiber.” Our data below clearly indicates that SCF indeed passes into the large intestine, as indicated by the large breath hydrogen response. In stark contrast, IMOs do not.
Skimping on fiber isn’t good for your digestive health, as it feeds the good bacteria in your GI tract, something that benefits you beyond adequate bowel movements. “The digestive tract is where your body’s second brain is, and it’s home to the majority of your immune system,” says Elia. “If you’re following keto, it should be one of your biggest priorities to make sure you get adequate fiber to keep your gut healthy and happy,” she adds. And, she notes, high-fat diets slow digestion and decrease GI motility, so it’s especially important to get enough.