The small intestine is the specific organ that extracts water and salt from food, says About.com. The digestive system as a whole contributes to nutrient absorption in the human body.
The salt and water come from ingested food and other digestive juices. The small intestine works to take in over a gallon of water every 24 hours. Although the process varies with different kinds of nutrients, the materials traverse the mucosa into the bloodstream and are transported to other areas of the body for further chemical processing. Carbohydrates, fats, protein and vitamins are other materials absorbed by the digestive system, according to About.com.