Digestion
Digestive Function
Also searched as Digestive Function.
You want it smooth: healthy digestion is the foundation of nutrition and gut-driven wellbeing.
In depth
Gastrointestinal function — the comfort and efficiency of digestion and nutrient absorption.
What drives it
Gut barrier increases it.
Intestinal-barrier review 2020 — a functional intestinal barrier enables nutrient and fluid absorption while excluding pathogens; gut microbiota sustains barrier integrity and aids digestion. PMC7463717
Mood (serotonin) increases it.
The same enterochromaffin 5-HT acts locally before it ever reaches the brain: EC-cell serotonin has direct physiological effects on gut motility, secretion and visceral sensation, and abnormal 5-HT regulation is implicated in gastrointestinal disorders and inflammatory bowel disease (PMC5165017). EC cells are mechanosensors — they translate the physical force of peristalsis into 5-HT and ATP release. PMC5165017
H. pylori reduces it.
About as close to proof as medicine gets, and it was obtained both ways: experimental ingestion of H. pylori caused gastritis in humans, and eradicating the organism resolved the inflammation (NCBI Bookshelf NBK2445). H. pylori infection causes chronic gastritis which can progress to peptic ulcer, gastric cancer and MALT lymphoma (PMC11558793), and it is a major cause of recurrent peptic ulcer disease. After eradication, ulcer rebleeding is close to abolished — cumulative incidence 0.5% over at least 12 months. PMC11558793
Pathogen tripwire reduces it.
Named across six gut-liver axis reviews. The main alteration is dysbiosis - A decrease in beneficial bacteria, an increase in potentially harmful microbes, and a loss of overall microbial diversity - with intestinal barrier integrity determining the levels of microbial metabolites, ENDOTOXINS and ammonia that reach the liver and systemic circulation. doi 10.1038/s41522-022-00352-6 · PMC11265038
Innate immune sensor reduces it.
Named across six gut-liver axis reviews. The main alteration is dysbiosis - A decrease in beneficial bacteria, an increase in potentially harmful microbes, and a loss of overall microbial diversity - with intestinal barrier integrity determining the levels of microbial metabolites, ENDOTOXINS and ammonia that reach the liver and systemic circulation. doi 10.1038/s41522-022-00352-6 · PMC11265038
Immune support increases it.
Named across six gut-liver axis reviews. The main alteration is dysbiosis - A decrease in beneficial bacteria, an increase in potentially harmful microbes, and a loss of overall microbial diversity - with intestinal barrier integrity determining the levels of microbial metabolites, ENDOTOXINS and ammonia that reach the liver and systemic circulation. doi 10.1038/s41522-022-00352-6 · PMC11265038
Calms inflammation reduces it.
Named across six gut-liver axis reviews. The main alteration is dysbiosis - A decrease in beneficial bacteria, an increase in potentially harmful microbes, and a loss of overall microbial diversity - with intestinal barrier integrity determining the levels of microbial metabolites, ENDOTOXINS and ammonia that reach the liver and systemic circulation. doi 10.1038/s41522-022-00352-6 · PMC11265038
Calms body-wide inflammation reduces it.
the main alteration of the gut-liver axis in chronic liver disease is dysbiosis, characterized by a decrease in beneficial bacteria, an increase in potentially harmful microbes, and a loss of overall microbial diversity. doi 10.1038/s41522-022-00352-6 · PMC11265038
Oxidative stress reduces it.
Named across six gut-liver axis reviews. The main alteration is dysbiosis - A decrease in beneficial bacteria, an increase in potentially harmful microbes, and a loss of overall microbial diversity - with intestinal barrier integrity determining the levels of microbial metabolites, ENDOTOXINS and ammonia that reach the liver and systemic circulation. (doi 10.1038/s41522-022-00352-6; doi 10.3389/fimmu.2025.1638197; PMC11265038; PMC12608333; doi 10.1016/j.jhep.2019.10.003). Verbatim: “Hyperoxia-induced oxidative stress is mediated by multiple molecular factors and leads to intestinal damage”. doi 10.1038/s41522-022-00352-6 · PMID 36901800 · PMC11265038
Calms histamine response reduces it.
Named across six gut-liver axis reviews. The main alteration is dysbiosis - A decrease in beneficial bacteria, an increase in potentially harmful microbes, and a loss of overall microbial diversity - with intestinal barrier integrity determining the levels of microbial metabolites, ENDOTOXINS and ammonia that reach the liver and systemic circulation. doi 10.1038/s41522-022-00352-6 · PMC11265038
Stress & cortisol reduces it.
The gut-brain axis. The strongest human number for this sits on the anxiety pathway: about half of adults treated for IBS also have an anxiety or depressive disorder. That is association, not direction, and this edge is drawn at that grade. doi 10.1038/s41522-022-00352-6 · PMC11265038
Lowers cortisol reduces it.
Named across six gut-liver axis reviews. The main alteration is dysbiosis - A decrease in beneficial bacteria, an increase in potentially harmful microbes, and a loss of overall microbial diversity - with intestinal barrier integrity determining the levels of microbial metabolites, ENDOTOXINS and ammonia that reach the liver and systemic circulation. doi 10.1038/s41522-022-00352-6 · PMC11265038
Gut-brain signal increases it.
The enteric nervous system and vagal signaling govern motility. doi 10.1038/s41522-022-00352-6 · PMC11265038
Micronutrient status increases it.
Named across six gut-liver axis reviews. The main alteration is dysbiosis - A decrease in beneficial bacteria, an increase in potentially harmful microbes, and a loss of overall microbial diversity - with intestinal barrier integrity determining the levels of microbial metabolites, ENDOTOXINS and ammonia that reach the liver and systemic circulation. doi 10.1038/s41522-022-00352-6 · PMC11265038
What it drives
It increases Micronutrient status.
10.1177/03946320241313426 — https://www.merckmanuals.com/professional/gastrointestinal-disorders/malabsorption-syndromes/overview-of-malabsorption — Digestive function determines absorption, and micronutrient is a node touching multiple outcomes here. A supplement that is not absorbed is not a dose. doi 10.1177/03946320241313426
It increases Mood.
10.3389/fendo.2022.817100 — This is what the symptom costs rather than what it causes physiologically. It is shown at reduced weight because no separate effect size has been reported for this arm. The asymmetry is deliberate and stated. The gut-brain axis; about half of adults treated for IBS also have an anxiety or depressive disorder, recorded on the anxiety node. This link rests on the reviews of this outcome as a whole, and no effect size specific to it has been reported. doi 10.3389/fendo.2022.817100
It increases Immune support.
10.3389/fimmu.2020.00282 — This is what the symptom costs rather than what it causes physiologically. It is shown at reduced weight because no separate effect size has been reported for this arm. The asymmetry is deliberate and stated. The gut is the largest mucosal immune surface, named in the gut-liver reviews. doi 10.3389/fimmu.2020.00282
It increases Liver.
10.1038/s41467-017-00796-x — Everything absorbed reaches the liver first through the portal vein. doi 10.1038/s41467-017-00796-x
It increases Gut barrier.
10.1038/s41467-017-00796-x — Digestive function and microbial ecology are mutually dependent. doi 10.1038/s41467-017-00796-x
It increases Insulin sensitivity.
10.1186/s12986-024-00789-w — low - nutrient delivery rate shapes the glycemic response. doi 10.1186/s12986-024-00789-w
It reduces Urate clearance.
The architecture is unusually clean and worth stating: gout has two separable stages. Stage one is metabolic - urate underexcretion through renal and gut mechanisms is the major mechanism for hyperuricemia in most people, via URAT1, GLUT9 and ABCG2. Stage two is immunological - MSU crystals function as damage-associated molecular patterns which, upon phagocytosis by macrophages, activate the NLRP3 inflammasome through a two-step process: priming via NF-kB signaling and activation via lysosomal rupture, potassium efflux, and mitochondrial ROS. And the two stages come apart in people: not all individuals with hyperuricemia show deposition of MSU crystals OR develop gout. Local factors decide - reduced joint temperature, low pH, high sodium concentration, and preexisting joint damage. A urate number is not a diagnosis. The treatment target is explicit: long-term lowering of serum urate to less than 360 MICROMOL/L leads to crystal dissolution and ultimately to suppression of flares. PMID 39712248 · PMC8268734
It increases Omega-3 status.
10.2147/vhrm.s50464 — Drawn from the reviews of this outcome. doi 10.2147/vhrm.s50464
It increases Vitamin D status.
NBK532266 — Drawn from the reviews of this outcome.
It increases Resists infection.
The headline on this pathway is a disappointment and it must stay there: the lack of effect of prophylactic vitamin C supplementation on the incidence of common cold in normal populations throws doubt on the utility of this wide practice. Regular supplementation decreases cold duration by 8 percent (3-12) and severity by 15 percent (CI 9-21) - but does not reduce how often you get one. With one striking exception that defines WHO it works for: a subgroup of six studies of marathon runners, skiers, and soldiers exposed to significant cold AND/OR physical stress experienced, on average, 50 percent reduction in common cold incidence. Extreme physical stress is the condition under which it prevents. PMC10712193
It increases Iron & oxygen carriage.
The mechanism that makes iron supplementation fail: anemia of inflammation is characterized by the insufficient production of erythropoietin and decreased response of erythroid progenitors to EPO. In addition, it inhibits the release of iron from the body stores and alters the iron status after being stimulated by hepcidin. Inflammation locks iron away - so oral iron given into an inflammatory state does not reach the marrow. Anemia affects 1.62 billion people. And the periodontal link is measured: a meta-analysis of sixteen studies on hemoglobin and iron metabolism in periodontitis - though the authors call the association still controversial and ask for larger cohorts. PMID 835510 · PMC7005133
It increases Liver clearance.
https://www.merckmanuals.com/professional/clinical-pharmacology/pharmacokinetics/drug-bioavailability — The aging outcome lists the thirteen hallmarks themselves, each mapped to its pathway and labeled with its hallmark number. (from the reviews of this outcome). Sources: PMC10132248; doi 10.1016/j.jhep.2023.03.017; PMC12673670. doi 10.1016/j.jhep.2023.03.017 · PMC10132248
It increases Thyroid.
10.1007/s12020-012-9814-9 — This link rests on the reviews of this outcome as a whole. No effect size specific to this arm has been reported, so it is shown at reduced weight. (from the reviews of this outcome). doi 10.1007/s12020-012-9814-9
It increases Hydration & electrolytes.
Intestinal absorption of water and electrolytes. PMC7005133
Blends that modulate it
Each blend page names this pathway and carries the study behind its claim.
See it on the map
Open the causal map to follow this pathway upstream and downstream, arrow by arrow, each with its study.