How Does Your Gut Work Anyway?

“It is hard to overstate how important gut health is to overall health and well-being" - Jenny, NP

Digestion is an intricate, highly coordinated process that breaks down the food we eat into nutrients, which the body uses for energy, growth, and cell repair. Understanding this journey from ingestion to excretion can provide insights into optimizing digestive health, a cornerstone of overall well-being. It’s important to emphasize the importance of not just what we eat, but how well our bodies process and utilize food.

Let’s look through the digestive process, highlighting each step and body part involved, energy utilization, waste elimination, and the benefits of a well-functioning digestive system.

The Mouth: The Starting Point of Digestion

Digestion begins in the mouth, where mechanical and chemical processes start breaking down food. Chewing (mastication) reduces food to smaller particles, increasing the surface area for enzymes to act upon. Saliva, produced by salivary glands, contains the enzyme amylase, which begins the breakdown of carbohydrates. This mixture of food and saliva, known as a bolus, is then swallowed and propelled into the esophagus.

The Esophagus: The Conduit

The esophagus is a muscular tube that connects the throat (pharynx) to the stomach. Peristalsis, a series of wave-like muscle contractions, pushes the bolus down the esophagus. At the end of the esophagus, the lower esophageal sphincter (LES) relaxes to allow the bolus into the stomach and then closes to prevent stomach contents from refluxing back into the esophagus.

The Stomach: The Mixing Chamber

The stomach plays a crucial role in both the mechanical and chemical aspects of digestion. Gastric juices, primarily hydrochloric acid (HCl) and the enzyme pepsin break down proteins and kill potential pathogens. The stomach lining is protected from these harsh conditions by a thick layer of mucus. The churning action of the stomach further mixes food with digestive juices, turning the bolus into a semi-liquid substance called chyme. This process can take several hours, depending on the complexity of the meal.

The Small Intestine: The Absorption Powerhouse

Chyme is gradually released into the small intestine, where most nutrient absorption occurs. The small intestine consists of three parts: the duodenum, jejunum, and ileum. The duodenum receives chyme from the stomach, along with bile from the liver and gallbladder, and pancreatic enzymes. These secretions neutralize stomach acid and further digest proteins, fats, and carbohydrates.

In the jejunum and ileum, the inner surface is lined with villi and microvilli, tiny hair-like structures that significantly increase the surface area for absorption. Nutrients pass through the intestinal lining into the bloodstream, which transports them to various tissues and organs. The absorbed nutrients include amino acids from proteins, simple sugars from carbohydrates, fatty acids, and glycerol from fats, vitamins, and minerals.

The Liver and Pancreas: The Supportive Organs

The liver and pancreas play essential roles in digestion. The liver produces bile, which emulsifies fats, making them easier to digest. Bile is stored in the gallbladder and released into the duodenum as needed. The pancreas produces a cocktail of digestive enzymes and bicarbonate, which are secreted into the small intestine to aid in the digestion of proteins, carbohydrates, and fats, and to neutralize stomach acid.

The Large Intestine: The Finishing Touch

Once most nutrients are absorbed, the remaining indigestible food residue, along with some water and electrolytes, enters the large intestine (colon). The primary functions of the large intestine are to absorb water and electrolytes from the remaining indigestible food matter and to form and store feces until defecation. Beneficial bacteria in the colon ferment some of the indigestible carbohydrates, producing short-chain fatty acids that are absorbed and used by the body.

The Rectum and Anus: The Exit

The final stage of digestion is the elimination of waste. Feces, the solid waste product, is stored in the rectum until it is expelled from the body through the anus during defecation. This process is regulated by the internal and external anal sphincters.

And that is it for the first part of this blog series! Part 2 will go over how you get as much energy and nutrients from food as you can and why good digestion matters. Part 3 will have the gold - tips on keeping your gut running like a well oiled machine!