Article highlights:
- Stress, processed foods, medications, and toxins can damage the gut lining and disrupt the microbiome.
- A weakened intestinal barrier may lead to inflammation, fatigue, food sensitivities, and chronic disease.
- Healthy habits like whole foods, fiber, sleep, and exercise help protect gut health and overall wellness.
Modern life is quietly wearing down your gut, and most people don’t realize it until symptoms start piling up. Stress, processed foods, medications, alcohol, and environmental toxins can disrupt the microbiome and weaken the intestinal lining, leading to increased intestinal permeability, or “leaky gut.” Over time, this leads to fatigue, brain fog, food sensitivities, immune imbalance, and accelerated aging. Your gastrointestinal system integrity and balance is critical to aging well and reclaiming your vitality.
The Gut Barriers
The adult small intestine is about 22-25 feet long with a surface area of 5,400 square yards. Its lining provides many diverse roles to protect you against the external environment and nourish your body. It is made up of 4 major layers that include:
1. microbial barrier or microbiome in the lumen of the intestines
2. biochemical barrier made up of water, mucous, immunoglobulin A, antibodies, and other natural antimicrobial immune substances
3. epithelial barrier is the third layer and undergoes renewal every 3-5 days
4. immunological barrier that contains an extensive network of lymph tissue or gut associated lymphoid tissues (GALT) making up the fourth outer layer
Epithelial Barrier, Tight Junctions and Selective Permeability
The epithelial barrier is of critical importance for maintaining health and preventing chronic breakdown that leads to a decline in health. In 1963, scientists first discovered specialized cells inside the intestinal epithelial barrier that became known as “tight junctions”. These unique cells are made up of various proteins like zonulin and occludin that act like doors and regulate the selective opening and closing of microscopic pores within the small intestine.
Tight junctions form a strong microscopic protective barrier that selectively allow digested food particles and water to pass through the vast area of the small intestine to nourish the rest of the body. Tight junctions also close or work to keep toxins, microorganisms, and other harmful substances within the intestinal lumen.
A great deal of information in recent years demonstrates the invaluable role of the intestinal barriers and tight junctions for health. Adverse changes to the intestinal barrier function and tight junctions, however, allow for increased intestinal permeability that insidiously provokes systemic inflammatory immune responses and erodes health.
Increased Intestinal Permeability Causes
Numerous environmental, dietary, and lifestyle habits have been found to disrupt the tight junctions and intestinal epithelial barrier. Contributing causes include:
• Alcohol
• Artificial sweeteners e.g. saccharin, acesulfame potassium, saccharin, sucralose
• Detergents and antimicrobial agents found in cleaning products
• Excessive endurance exercise
• Food emulsifiers, e.g. mono- and diglycerides or esters of fatty acids, carboxymethylcellulose (CMC) and polysorbate 80
• Gluten
• Gut dysbiosis and infections
• High stress
• Increased blood sugar levels
• High consumption of omega-6 seed oils (vegetable, corn, soy, safflower, sunflower, canola, etc.)
• Insufficient dietary fiber
• Microplastics
• Mycotoxins
• Numerous medications (see below)
• Pesticide/herbicide residues in food supply
• Pregnancy
• Restrictive diets
• Shift work
• Western diet: high fat, fructose, sugar, salt intake
• Other
Drug-Induced Gut Dysbiosis and Permeability
A brief focus on drug-induced gut dysbiosis and permeability is important as at least 50 percent of the American population has used at least one medication in the last 30 days. A 2020 publication in Nature Communication showed that 19 of 41 classes of medications interfered with the gut microbiome causing dysbiosis that can contribute to increased intestinal permeability creating systemic adverse effects. Antimicrobial drugs can also disrupt the microbiome in the skin, mouth, respiratory and genitourinary tracts. Please check in with your prescribing practitioner to evaluate your medication needs and concerns.
Gut disturbing drug classes identified currently include:
• antibiotics
• antidepressants
• antidiabetics Metformin/GLP-1, sulfonylureas
• antifungals
• antiparasitic
• antipsychotics
• antivirals
• acetaminophen
• chemo drugs
• immunosuppressants
• laxatives
• NSAIDs (e.g. ibuprofen, aspirin, etc.)
• polyethylene glycol
• PPI proton pump inhibitors/antacids
• statins – cholesterol lowering medications
• steroids
Effects and Disorders Linked with Increased Intestinal Permeability and Dysbiosis
Dysbiosis provoked by drugs, Western diet, or other factors can lead to increased intestinal permeability resulting in loss of microbial diversity, interference with nutrient absorption and vitamin production, and increased immune cell activation provoking localized inflammation.
As this process continues with ongoing exposures, the inflammatory reactions expand further and deeper, disturbing the integrity of all the intestinal barriers crossing into circulation creating a host of disorders throughout the body including, but not limited to:
• Allergies, food sensitivity, eczema
• Arthritis/osteoarthritis
• Attention deficit hyperactivity disorders (ADD/ADHD)
• Autoimmune disorders such as ankylosing spondylitis, Hashimoto’s, Grave’s disease, rheumatoid arthritis, multiple sclerosis, SLE/lupus
• Cancer
• Cardiovascular disease, hyperlipidemia/elevated cholesterol
• Celiac disease
• Chronic Fatigue Syndrome/Myalgic Encephalomyelitis, Covid-19
• Chronic Kidney Disease
• Depression and Anxiety
• Diabetes – pre-diabetes, type I, type II, gestational diabetes
• Esophageal and gastrointestinal cancers
• Esophageal disorders, i.e. Barrett’s esophagus, GERD
• H. pylori related disorders
• Hypertension
• Inflammatory Bowel Disease, Crohn’s disease, Ulcerative colitis, other forms of colitis
• Irritable Bowel Syndrome, SIBO, ulcers
• Liver diseases like cirrhosis, fatty liver/NAFLD, fibrosis
• Neurodegeneration, Alzheimer's, Parkinson, others
• Non-celiac gluten sensitivity
• Obesity
• Osteoporosis, post-menopausal and age-related
• Schizophrenia
• Sepsis
Intestinal Permeability and Neurodegeneration
A cutting-edge March 2026 study furthermore brought to light the connection of the increased intestinal permeability to neurodegenerative changes. This animal study showed that increased intestinal permeability caused by the Western diet leads to movement of bacteria in the gut up to the brain by traveling along the vagus nerves without any detectable amounts found in the blood or other tissues.
The types of bacteria found in low levels in brain tissues correlated with animal studies demonstrating neurodegenerative changes with Alzheimer’s, Parkinson, etc. When mice reverted to a healthier diet, the brain bacterial load decreased and gut lining integrity was restored. The results suggested that development of neurodegenerative conditions like Alzheimer’s, Parkinson’s, and others may be initiated from movement of gut bacteria to the brain because of increased intestinal permeability.
Untold Burden on American Health
The Western diet, polypharmacy, and environmental toxins are secretly wrecking the health of the American population. Untold numbers of individuals unknowingly have compromised gut health with dysbiosis and increased intestinal permeability undermining their health. Epidemic levels of obesity, diabetes, cancer, autoimmune disorders, neurodegenerative diseases, arthritis, mental health challenges, liver and kidney disease, etc. are occurring in individuals of all ages.
Intestinal barrier function and the 70 trillion gut microbiome are directly impacted by the things you consume daily as well as stress and activity levels. To maintain or restore health, reduce as many health challenges as possible, provide your body with a variety of whole, real foods, and get plenty of rest and moderate exercise.
Additional Resources
Real Foods and Flavonoids Protect Your Body from Stress and Aging
