The Science Behind Leaky Gut, the Gut Microbiome, and Arthritis

A lot of people remain skeptical of the theory that arthritis symptoms can be caused or worsened by problems in the gut. But research strongly suggests connections between leaky gut, the gut microbiome, and arthritis. ¹ Campbell AW. Autoimmunity and the gut. Autoimmune Dis. 2014;2014:152428.

This page provides in-depth descriptions of leaky gut and the gut microbiome, and how experts believe they are involved in the development of food sensitivities and arthritic disease.

Leaky Gut

Medical professionals sometimes refer to leaky gut as high intestinal permeability. The small and large intestines connect the stomach to the colon.

Healthy intestines are naturally permeable, allowing tiny nutrient particles to flow through their lining and enter the bloodstream. Problems arise if the intestinal lining becomes damaged:

• A damaged intestinal lining is too permeable, allowing larger, undigested food particles (for example, gluten proteins) and intestinal microbes to escape into the bloodstream.
• The food particles that leak into the bloodstream are viewed by the immune system as foreign bodies, causing an immune system reaction.
• The microbes that escape into the bloodstream can also cause an immune system reaction. These microbes are often gram-negative gut bacteria whose outer membranes contain molecules called lipopolysaccharides (LPS). Lipopolysaccharides trigger the immune system. ² Alexander C, Rietschel ET. Bacterial lipopolysaccharides and innate immunity. J Endotoxin Res. 2001;7(3):167-202. ^{, 3} Lin R, Zhou L, Zhang J, Wang B. Abnormal intestinal permeability and microbiota in patients with autoimmune hepatitis. Int J Clin Exp Pathol. 2015;8(5):5153-60.
• An activated immune system produces antibodies that can travel in the bloodstream and create an inflammatory response in other parts of the body, including joints, leading to arthritic pain and swelling.

Forms of spondyloarthritis, such as ankylosing spondylitis, and psoriatic arthritis, are associated with Crohn’s disease and ulcerative colitis, which affect the intestinal lining.

See Conditions Related to Inflammatory Arthritis

The causes of leaky gut
Evidence suggests many factors can contribute to leaky gut, including stress; eating pesticide-laden foods; and an overgrowth of bacteria in the small intestine (SIBO). This overgrowth can be caused by long-term use of antacids, antibiotic use, and eating a standard Western diet full of processed foods.

Leaky gut is controversial
Readers should keep in mind that while a growing number of physicians believe leaky gut is the underlying cause of many medical conditions, many do not. Leaky gut and its possible connection to arthritic disease is not part of most standard medical school curriculums.

Scientists do know that intestinal health is correlated with the health of the gut microbiome.

The Gut Microbiome

The gut microbiome includes bacteria and other microbes that naturally live along the digestive tract, from the mouth to the anus. Most of the gut’s microbes are located in the intestines.

Gut bacteria produce important chemical compounds
Gut bacteria produce chemical compounds ⁴ Arumugam M, Raes J, Pelletier E, Le Paslier D, Yamada T et al (2011) Enterotypes of the human gut microbiome. Nature 473: 174–180 
 that:

• Affect many biological functions, such as immunity, nutrient absorption, and sleep. If the gut microbiome is disrupted and becomes imbalanced, biological functions will be disrupted, too.
• Can be beneficial. ⁵ Conlon MA, Bird AR. The impact of diet and lifestyle on gut microbiota and human health. Nutrients. 2014;7(1):17-44. For example, gut bacteria that thrive on fiber-rich foods produce short-chain fatty acids, which contribute to the health of the intestinal lining and may prevent disease. ⁶ Wong JM, De souza R, Kendall CW, Emam A, Jenkins DJ. Colonic health: fermentation and short chain fatty acids. J Clin Gastroenterol. 2006;40(3):235-43. ^{, 7} Havenaar R. Intestinal health functions of colonic microbial metabolites: a review. Benef Microbes. 2011;2(2):103-14. ^{, 8} Russell WR, Hoyles L, Flint HJ, Dumas ME. Colonic bacterial metabolites and human health. Curr Opin Microbiol. 2013;16(3):246-54.
• Can be harmful. Certain types of bacteria thrive on a high-protein, low-fiber diet and produce ammonia and other compounds that have potentially harmful health effects.

A healthy gut microbiome is diverse and balanced
In general, microbial diversity is associated with good health. ⁹ Blaser MJ, Falkow S. What are the consequences of the disappearing human microbiota?. Nat Rev Microbiol. 2009;7(12):887-94. A normal, healthy gut microbiome includes a diverse population of bacteria and other microbioal species that keep each other in check.

See Gut Microbiome Health and Diversity

If the populations of certain microbial species grow too big, and other populations shrink or disappear, the gut’s microbiome can become imbalanced. This condition is called dysbiosis. Dysbiosis is associated with rheumatoid arthritis, ankylosing spondylitis, psoriatic arthritis, and other autoimmune diseases. ¹⁰ Round JL, Mazmanian SK. The gut microbiota shapes intestinal immune responses during health and disease. Nat Rev Immunol. 2009;9(5):313-23.

See Inflammatory Arthritis

Diet affects the microbiome
Different bacteria thrive on different foods. Many types of beneficial bacteria absorb nutrients from leafy greens, vegetables, and other high-fiber foods. Eating these foods can help populate the gut with more beneficial bacteria.

Repairing Leaky Gut and Gut Dysbiosis

A healthy, balanced microbiome fosters healthy intestines, and vice versa—and both affect a person’s overall health.

See Reduce the Risk of Arthritis by Improving the Microbiome

Changes in diet can help foster beneficial bacteria and heal the gut wall. These changes can lead to a better functioning immune system, less inflammation, and less arthritis pain. The next page contains specific dietary recommendations.