Gut Barrier Support:
fulvic acid, humic acid and intestinal barrier repair
How do fulvic acid and humic acid act on the gut barrier, what are the mechanisms behind chelation and tight junction repair, and what does the most recent veterinary cell biology study show? For dogs, cats and humans.
By Stefan Veenstra DVM
Humic substances: the organic processors of organic matter
Humic substances are the end products of the microbial and chemical decomposition of organic matter in soil and water. They consist of a continuum of molecular weights and are traditionally classified into three fractions: fulvic acid (low-molecular, water-soluble at all pH levels), humic acid (high-molecular, soluble at high pH) and humin (non-water-soluble). In agriculture and livestock farming, humic substances have been used for decades as soil improvers and feed additives, but the mechanistic basis for their effect in the intestinal environment has only been scientifically mapped in recent years. [1]
Fulvic acid and humic acid contain a rich variety of functional chemical groups: carboxyl groups, hydroxyl groups, phenolic groups and carbonyl groups. This oxygen-rich structure gives humic substances their unique chelating capacity, ion exchange capacity and biological activity. As the smallest fraction, fulvic acid has the highest functional group concentration by weight and the strongest biological activity in the intestinal environment.
NGD Care Gut Protocol: Phase 2 Component for Bowel Wall Repair (Alternative for Animals in Addition to Shilajet)
NGD Care Giardia Protocol: Intestinal Barrier Restoration After Parasitic Infection
The intestinal barrier: structure and vulnerability
The intestinal barrier is a multi-layered protection between the intestinal lumen and the systemic circulation. The physical basis is formed by the monolayer of enterocytes that are connected to each other via tight junctions (especially claudine, occludine and ZO-1). In addition, the mucus layer, produced by goblet cells, provides a chemical barrier that keeps pathogens and toxins at bay. When these layers are affected, we speak of increased intestinal permeability. [2]
In dogs and cats with chronic enteropathy, IBD, dysbiosis or post-infectious intestinal damage, tight junction proteins have been shown to be reduced in expression. This leads to leakage of bacterial LPS into the systemic circulation. This chronically activates the immune system, which causes complaints far outside the intestine via the gut-immune axis, the gut-skin axis and the gut-brain axis. [3]
Humic acid: barrier repair and inflammation inhibition in canine intestinal cells
The most direct veterinary evidence for humic acid in gut barrier repair was published in January 2026. Móritz et al. published a cell biology study in Animals (MDPI) in which humic acid was tested on canine intestinal epithelium (IPEC-J2) and canine immune cells (PBMCs). Measured were paracellular permeability via FITC dextran passage and pro-inflammatory cytokines (TNF-alpha, IL-6) after LPS challenge. [4]
The results showed that humic acid maintained epithelial barrier integrity under LPS stress and significantly reduced pro-inflammatory cytokine production. This is the first study to demonstrate this mechanism directly in canine cells and provides a direct cell biological basis for the clinical use of humic acid in intestinal barrier support in dogs.
Darmepithelium (IPEC-J2): humic acid reduced FITC-dextran passage (measure of paracellular permeability) in LPS stress the barrier integrity was better preserved.
Canine immune cells (PBMCs): humic acid decreased TNF-alpha and IL-6 production with LPS stimulation the inflammatory response to LPS leakage was inhibited.
Authors’ conclusion: Humic acid is a promising nutraceutical for gut barrier function and inflammation control in dogs with chronic enteropathy.
Fulvic acid: transporter, chelator and microbiome modulator
Fulvic acid has a fundamentally different action profile than humic acid due to its small molecular size. It can cross cell membranes and acts as an intracellular mineral transporter, which significantly improves the uptake of trace minerals such as zinc, manganese, iron, and selenium compared to inorganic mineral salts. [5]
As a chelating agent, fulvic acid binds heavy metals (lead, mercury, cadmium, arsenic) and mycotoxins via coordinateative binding to its carboxyl and hydroxyl groups. Bound toxins are not absorbed but excreted through faeces, which reduces the enterohepatic recirculation of toxins. A study in poultry (2022) showed that fulvic acid supplementation improved gut barrier function, favorably altered microbiome composition, and reduced ammonia emissions, measured via multiple objective parameters. [6]
Winkler and Ghosh (2018) described in a review in the Journal of Diabetes Research the immune-modulatory and anti-inflammatory properties of fulvic acid via NF-kB inhibition, a mechanism that is particularly relevant in chronic intestinal inflammation and increased permeability. [7] Fulvic acid additionally stimulates Akkermansia muciniphila, the key species for tight junction expression and mucus layer buildup, which complements prebiotic microbiome activity.
Complementary mechanisms of the combination
Position in the NGD Care Bowel Protocol
In the NGD Care Bowel Protocol, phase 2 focuses on intestinal wall repair. For humans, shilajit is the first choice in this phase as a concentrated source of fulvic acid, minerals, and dibenzo-alpha-pyrones with supplemental mitochondrial support. For animals, fulvic and humic acids via Gut Barrier Support are a direct, well-founded option: the intestinal barrier mechanisms of action are similar and in the case of humic acid now also directly demonstrated in canine cells.
Gut Barrier Support is particularly relevant in animals where intestinal damage is central (post-infectious, chronic IBD, toxic load) and where the emphasis is on barrier repair and detoxification over mitochondrial support. In the case of extensive mitochondrial exhaustion, supplementation with shilajet or Longevity Complex (phase 3 of the protocol) makes more mechanistic sense.
Scope of application Gut Barrier Support: dog, cat and human
Increased intestinal permeability and leaky gut. Chronic intestinal complaints with systemic inflammatory component (skin problems, allergies, behavioral changes). Post-infectious bowel recovery after Giardia, antibiotics, or deworming. Toxic load due to heavy metals, mycotoxins or environmental pollution. Poor nutrient absorption despite adequate nutrition. Phase 2 component of the Intestinal Protocol in dogs and cats. Supplement to the Giardia Protocol for barrier repair after intestinal damage.
Conclusion
Gut Barrier Support combines two complementary human substances, each of which employs a fundamentally different mechanism: fulvic acid as a transporter, chelator and microbiome modulator, and humic acid as a barrier repairer and anti-inflammatory. The first veterinary cell biology study specifically in canine intestinal cells (Móritz et al., 2026) confirms the mechanistic basis for humic acid in intestinal barrier support in dogs.
Gut Barrier Support is a valuable component of the Animal Gut Protocol, and a broadly applicable supplement in all clinical situations where gut barrier repair and toxin clearance are prioritized. Always as part of an integral bowel protocol, in consultation with an (integrative) veterinarian.
View Gut Barrier Support in the NGD Care webshop
Literature
- Stevenson FJ, et al. Humus Chemistry: Genesis, Composition, Reactions. 2nd ed. Wiley; 1994. [Classification and chemistry of humic substances]
- Camilleri M, Madsen K, Spiller R, Greenwood-Van Meerveld B, Verne GN. Intestinal barrier function in health and gastrointestinal disease. Neurogastroenterol Motil. 2012; 24(6):503-512.
- Jergens AE, Heilmann RM. Canine chronic enteropathy: current state-of-the-art and emerging concepts. Front Vet Sci. 2022;9:923013. [Intestinal Barrier Dysfunction in Canine Chronic Enteropathy]
- Móritz AV, Farkas O, Jerzsele A, Palkovicsné Pézsa N. Protective effects of humic acid on intestinal barrier dysfunction and inflammatory activation in canine cell-based models. Animals. 2026; 16(2):173. doi:10.3390/ani16020173. [First Veterinary Cell Biology Study on Humic Acid in Canine Intestinal Cells 2026]
- Schepetkin IA, Xie G, Kirpotina LN, et al. Macrophage immunomodulatory activity of polysaccharides isolated from Oplopanax horridus. Int Immunopharmacol. 2009; 9(9):1022-1030. [Fulvic Acid as a Mineral Transporter and Immunomodulator]
- Effects of fulvic acids on gut barrier, microbial composition, fecal ammonia emission, and growth performance in broiler chickens. Poultry Science. 2022. doi:10.1016/j.psj.2022.102069.
- Winkler J, Ghosh S. Therapeutic potential of fulvic acid in chronic inflammatory diseases and diabetes. J Diabetes Res. 2018;2018:5391014.
This information is educational in nature and based on available scientific literature. The studies mentioned are not always directly veterinary or specific to the formulation described here. This text does not replace a veterinary consultation and does not contain any therapeutic claims.