Which substance is primarily absorbed in the large intestine?

The substance primarily absorbed in the large intestine is water. The large intestine plays a crucial role in the final stages of digestion, where it is responsible for absorbing the majority of the water from indigestible food matter. This process is essential for maintaining hydration and ensuring that waste products are properly formed into stool.

In addition to water, the large intestine also absorbs some electrolytes and certain vitamins produced by the gut bacteria, such as Vitamin K and some B vitamins. However, these contributions are smaller in comparison to the absorption of water.

Proteins and carbohydrates are primarily digested and absorbed in the small intestine. Therefore, their absorption does not largely occur in the large intestine, making water the clear primary substance absorbed in this part of the digestive system.