Black beans contain an impressive total amount of fiber (about 15 g per cup) and protein (close to 15 g per cup). These can help regulate the passage of food through your digestive tract and stabilize the flow of digestion. This is believed to help regulate blood sugar levels and the overall health of the digestive tract. Also, these legumes have unique qualities: their fiber is a valuable source of resistant starch. This is because it "resists," it doesn't break down, and therefore does not cause an undesirable increase in your blood sugar level.  Resistant starch is counted as calories on labels and charts, but 90% of resistant starch calories are lost during digestion, acting more like a type of fiber. Let me explain. Let's say you eat about 41 grams of total carbohydrate. About 15 of those grams are classified as fiber. If you subtract them from the total amount of carbohydrates, you end up with 26 g, which contains lots of starch.  Usually, this high starch content would increase a food's Glycemic Index value and make it a food of concern concerning blood glucose and insulin impact.  However, in the case of black beans, these concerns are not raised because a large amount of the starch in black beans "resists" digestion, as I said earlier, and goes straight through, if you will, like water through a sieve.  Recent studies show that black beans contain unique components that also improve the regulation of blood sugar and insulin levels on the protein side.