The small intestine’s main job is to finish digesting food and absorb almost all the nutrients and much of the water your body needs.

Quick Scoop

  • It completes chemical digestion of carbohydrates, proteins, and fats using enzymes and bile.
  • It absorbs about 90% of nutrients (sugars, amino acids, fatty acids, vitamins, minerals, and electrolytes) into the blood and lymph through its villi and microvilli.
  • It also absorbs a large amount of water, helping form liquid contents before they move to the large intestine.
  • It turns what’s left into waste that passes on to the large intestine.
  • It has immune and hormone roles, acting as a barrier to harmful bacteria and releasing hormones that control digestion and appetite.

So in one line: the function of the small intestine is to digest food into small molecules, absorb them into the body, and pass the remaining waste onward.