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Who’s ready for a little throwback to biology in school? The intestines were perhaps the most fun to draw or mark, right? We all know that its basic job is to take in food, digest it to extract and absorb energy and nutrients, and expel the rest. Most nutrients are absorbed in the small intestine whose walls allow substances to reach the blood and all our organs. The large intestine absorbs the water present in the indigestible part of the food. Thereafter, the waste is passed out from the body as faeces.

At 7 meters, the intestine is the longest internal organ of the human body and is the final part of the digestive system. There are four key functions that our intestines carry out.

Metabolic, trophic (nutritive), protective and immunological.

Metabolic function

Allows the absorption of ions (calcium, magnesium and iron), the synthesis of some vitamins (folic acid, vitamin K, B vitamins) and the formation of short-chain fatty acids. It also ensures the formation of B vitamins. The gut bacteria work relentlessly, transforming waste into substances useful for the body such as acetic acid, the propionic or butyric.

Trophic function (nutritive)

Ensures the nourishment of intestinal cells to promote physiological activity of the colon, also through the production of short-chain fatty acids such as butyric. Short-chain fatty acids have been shown to stimulate the proliferation of cells that cover the internal surface of the intestine.

Immunological function

Essentially a defence function, where the bacterial flora keeps the tissue lymphatic system active. It helps when the body needs to fight bacteria or harmful substances. It is in the lymphatic system that the production of substances and cells that constitute the body's immune response takes place.

Protective function

Defends the gastrointestinal tract from pathogens. This function is ensured by saliva, gastric acids, peristalsis, cell membranes that cover the internal surface of the intestine (epithelial) and naturally by the flora. The gut bacterial flora acts through mechanisms of competition with pathogenic bacteria and produces specific protein substances such as bacteriocins that attack them directly.