Obtaining nutrients from food involves both digestion and absorption, which are critical for healthy metabolism. Digestion is the process of breaking down food into pieces from which nutrients can be absorbed into the body and dispersed to tissues as needed. Digestion also involves removing the waste, which is anything the body cannot use.

Digestion begins in the mouth with the mechanical breakdown of food through chewing, followed by chemical breakdown by enzymes found in saliva. From the mouth, the bolus, or chewed food, will travel to the stomach, where it encounters a highly acidic environment. The stomach contains digestive enzymes that begin to degrade whole food pieces into basic components that can be absorbed.

Next, the contents from the stomach, called chyme, enter the small intestine. As they travel, secretions from the liver, pancreas and gallbladder aid in digestion through the release of digestive juices that help further break down food. The majority of nutrients are now able to be absorbed throughout the small intestine. Folate, iron and vitamin D3 are absorbed in the duodenum portion of the small intestine, while the jejunum is the site of absorption for sugars, amino acids and fatty acids. Finally, the ileum is critical for fluid and vitamin B12 absorption.

While most of the absorption of nutrients occurs in the small intestine, the large intestine houses very important microbiota that constitute part of the gut microbiome. These bacteria are critical to the health of the entire body, and can use food components that are non-digestible by intestinal cells such as dietary fiber. Maintaining a healthy microbiome provides benefits to the brain, immune system and many other parts of the body. The large intestine is also the location for absorption of sodium and potassium, as well as reabsorption of water. Leaving the large intestines, the remaining byproducts of food that were not digested or absorbed are eliminated via defecation.

The breakdown and digestion of foods is a highly complex and regulated task, orchestrated by several organs. To keep the digestive tract running smoothly, focus on consuming a whole food, plant-based diet and obtaining adequate sleep and physical activity.