Dietary Fiber in Digestive Health

Why can’t humans digest dietary fiber when we can digest starch?

Humans cannot digest dietary fiber because they lack the necessary enzyme to break it down. Dietary fiber is a complex carbohydrate that consists of long chains of sugar molecules, specifically cellulose and other non-starch polysaccharides. On the other hand, starch is a digestible carbohydrate made up of shorter chains of sugar molecules called glucose.

Digestion of starch begins in the mouth with the enzyme amylase, which breaks it down into smaller polysaccharides and maltose. Further breakdown occurs in the small intestine with the help of pancreatic amylase. Eventually, the enzyme maltase breaks down maltose into glucose, which can be absorbed by the body for energy

However, in the case of dietary fiber, humans lack the specific enzyme necessary to break down its complex structure. While some animals, like cows and termites, possess the enzyme cellulase to digest fiber, humans do not produce enough of this enzyme

Nonetheless, even though dietary fiber is not broken down, it still plays a vital role in our digestive system. The undigested fiber adds bulk to our stool, which helps regulate bowel movements and prevent constipation. Additionally, fiber also provides other health benefits such as promoting a healthy gut microbiome, lowering cholesterol levels, and regulating blood sugar levels

Therefore, even though humans cannot digest dietary fiber like they can starch, it is still an essential part of a healthy diet and plays an important role in overall digestive health

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