Bananas are a fascinating fruit in terms of their carbohydrate and sugar content. Even though bananas are a fruit that tastes quite sweet when ripe—containing 14-15 grams of total sugar—bananas receive a rating of low in their glycemic index (GI) value. GI measures the impact of a food on our blood sugar. This low GI value for bananas is most likely related to two of their carbohydrate-related qualities.
First, as mentioned previously, a medium-size banana contains about 3 grams of total fiber. Fiber is a nutrient that helps regulate the speed of digestion, and by keeping digestion well-regulated, conversion of carbohydrates to simple sugars and release of simple sugars from digesting foods also stays well-regulated.
Within their total fiber content, bananas also contain pectins. Pectins are unique and complicated types of fiber. Some of the components in pectins are water-soluble, and others are not. As bananas ripen, their water-soluble pectins increase, and this increase is one of the key reasons why bananas become softer in texture as they ripen. As their water-soluble pectins increase, so does their relative concentration of fructose in comparison to other sugars. This increase in water-soluble pectins and higher proportional fructose content helps normalize the rate of carbohydrate digestion and moderates the impact of banana consumption on our blood sugar. The bottom line here are some surprisingly digestion-friendly consequences for a fruit that might be casually dismissed as being too high in sugar to be digestion-friendly.
Similar to the importance of their water-soluble pectins is the digestive importance of fructooligosaccharides (FOS) in bananas. FOS are unique fructose-containing carbohydrates that are typically not broken down by enzymes in our digestive tract. Instead, they move along through the digestive tract until they reach our lower intestine and get metabolized by bacteria. This process helps maintain the balance of “friendly” bacteria (for example, Bifidobacteria) in our lower intestine, and as a consequence, it also supports our overall digestive health.
In one study involving female participants, eating two bananas each day for two months led to significant increases in Bifidobacteria. Along with these increased levels of Bifidobacteria, participants also experienced fewer gastrointestinal problems and more regular bowel function when compared to other women in the study who drank a banana-flavored beverage that did not contain any actual banana.