The "D" in DIGIN: Digestion Is the Foundation of Gut Health

When patients tell me they eat well but still feel bloated, exhausted, or nutrient-deficient despite a healthy diet, I usually start by asking: Are you actually digesting the food you eat? Because it doesn't matter how healthy your meals look if your body can't break them down and absorb what it needs.

Digestion is not automatic

We often assume digestion just happens: you eat and your body takes care of the rest. In reality, digestion is an energy-intensive, neurologically coordinated process. It requires thorough chewing to mechanically break food into small pieces, adequate stomach acid to denature proteins and activate enzymes, timely pancreatic enzyme release to continue breaking down fats, proteins, and carbohydrates, coordinated bile secretion to emulsify fats, and a calm enough nervous system to allow all of this to occur.

Chewing is where this cascade begins. It reduces the mechanical workload on everything downstream and signals the brain to activate salivary enzymes, gastric acid, and pancreatic secretions before food even reaches the stomach. That preparatory cascade depends entirely on your nervous system state. Eating while rushed, distracted, or stressed keeps you in sympathetic mode, the "fight or flight" state that actively diverts resources away from digestion. Blood flow shifts to muscles, enzyme secretion drops, and motility slows. Even slowing down for the first few bites, taking a breath before meals, or stepping away from screens can be enough to meaningfully shift that balance.

Stomach acid: more often too low than too high

Heartburn and reflux are almost universally attributed to excess stomach acid. In practice, the opposite may be equally common: insufficient acid production, or hypochlorhydria.

Stomach acid does more than just break down food. It denatures proteins and prepares them for enzymatic digestion, activates pepsin (the primary protein-digesting enzyme in the stomach), creates an inhospitable environment for most ingested bacteria and parasites, facilitates absorption of iron, calcium, magnesium, and zinc, and triggers release of intrinsic factor, which is essential for vitamin B12 absorption.

When acid production is low, protein stays inadequately broken down. Larger polypeptide fragments move into the small intestine, where they undergo bacterial fermentation. That fermentation produces gas and pressure, which can push the lower esophageal sphincter open and allow stomach contents to reflux upward, creating heartburn that paradoxically mimics too much acid. When we reflexively prescribe proton pump inhibitors to suppress acid, symptoms may improve initially as acid drops below the threshold needed to irritate the esophagus, but the underlying digestive dysfunction persists.

Pancreatic enzymes and bile: the silent workhorses

Once food leaves the stomach and enters the small intestine, pancreatic enzymes and bile carry the digestion forward. When pancreatic function is impaired, people often notice bloating after meals, particularly following fatty foods. Stools may appear pale, greasy, or float, signs of fat malabsorption called steatorrhea. Over time, deficiencies in fat-soluble vitamins (A, D, E, K) develop.

A simple stool test measuring fecal pancreatic elastase assesses exocrine pancreatic function. Low levels indicate the pancreas is not producing adequate enzymes, pointing to a mechanical explanation for symptoms often dismissed as generic food intolerance.

Bile, produced by the liver and stored in the gallbladder, emulsifies fats. It breaks large fat globules into smaller droplets that digestive enzymes can access efficiently, and it also helps regulate gut microbial composition and facilitates absorption of fat-soluble vitamins and essential fatty acids. When bile flow is sluggish, from gallbladder dysfunction, liver congestion, or bile acid insufficiency, fat digestion becomes suboptimal and the microbial ecosystem can shift unfavorably.

Why poor digestion creates downstream problems

When food is not fully broken down in the stomach and upper small intestine, several cascading problems emerge. Larger, partially digested food particles move through the GI tract and become substrates for bacterial fermentation in areas where fermentation should be minimal, producing gas, bloating, and altered bowel patterns.

The immune system then encounters incompletely digested proteins, larger peptide fragments more likely to be recognized as foreign. Immune reactions follow that would not occur if proteins had been properly reduced to amino acids. Chronic exposure to partially digested food wears down the gut barrier's tight junctions, which we explore in the next post. As the barrier becomes more porous, immune activation intensifies, feeding a cycle of inflammation and food reactivity.

One pattern I observe regularly: when digestion is properly supported, food sensitivities frequently diminish or resolve entirely. The foods weren't inherently problematic. The body simply lacked the capacity to process them. When digestion improves, the intolerances go away.

Clinical patterns that suggest impaired digestion

Digestive insufficiency tends to show up through bloating that begins soon after eating (especially following protein or fat-rich meals), feeling full quickly or experiencing prolonged heaviness after moderate portions, fatigue or mental fog after meals, frequent belching or reflux, visible undigested food in stool, an expanding list of food intolerances, and signs of nutrient deficiency (brittle nails, thinning hair, persistent fatigue) despite adequate dietary intake.

Restoring the foundation

Supporting the digestive foundation requires more than replacing what is missing. We begin by removing barriers: addressing chronic stress and identifying medications that may impair secretions. We then move to the Replace phase of the 5R protocol, using targeted supports such as Betaine Hydrochloride with pepsin, broad-spectrum digestive enzymes, or digestive bitters to stimulate the body's natural output.

The goal is to restore the body's innate physiological capacity. Digestion is the gatekeeper of your biology—the process that turns the outside world into "you." When this foundation is secure, we set the stage for healing the intestinal barrier and balancing the complex microbial ecosystem that follows.

Digestion is the gatekeeper of human biology. It is the process that converts the external world into the building blocks of your cells. When this foundation is secure, the rest of the gut can begin to heal. In our next post, we will move to the first "I" in DIGIN—Intestinal Permeability—to explore what happens when the gut barrier fails and the immune system goes on the offensive.

References

• Age-Related Changes of the Gastrointestinal Tract. Pilotto A, Custodero C, Crudele L, et al. The Lancet. Gastroenterology & Hepatology. 2026;11(1):59-70. doi:10.1016/S2468-1253(25)00235-3.

• The Risks and Benefits of Long-Term Use of Proton Pump Inhibitors: Expert Review and Best Practice Advice From the American Gastroenterological Association. Freedberg DE, Kim LS, Yang YX. Gastroenterology. 2017;152(4):706-715. doi:10.1053/j.gastro.2017.01.031.

• AGA Clinical Practice Update on the Epidemiology, Evaluation, and Management of Exocrine Pancreatic Insufficiency: Expert Review. Whitcomb DC, Buchner AM, Forsmark CE. Gastroenterology. 2023;165(5):1292-1301. doi:10.1053/j.gastro.2023.07.007.

• ACG Clinical Guideline: Small Intestinal Bacterial Overgrowth. Pimentel M, Saad RJ, Long MD, Rao SSC. The American Journal of Gastroenterology. 2020;115(2):165-178. doi:10.14309/ajg.0000000000000501.