12 Health Conditions Linked to Your Gut and an Imbalanced Microbiome

26/07/2022 • Laura Kunces, PhD, RD, CSSD

The earliest gut microbiome findings date to European scientists in the 1840s, and it wasn’t much after that when it was realized there are both “good” and “bad” microbes that live inside us. Although clinical and benchtop researchers have spent 180 years exploring the linkage of the gut microbiome to health, disease, and human performance, the immense public interest in the gut microbiome skyrocketed at the time of 2012’s publication of the Human Microbiome Project.

Thanks to modern media, technological advances, and at-home testing, the world is much better educated on the powerful effects of gut microbes, and we can evaluate our own health and wellness from the comfort of our bathroom.

This article highlights 12 scientifically backed health concerns linked to the balance of microbes in the gut via several mechanisms and pathways. The common thread between these conditions and gut health is one thing – an imbalance of the microbes in the gut known as dysbiosis.

1. Weight Gain/Obesity

Two of five U.S. adults are considered obese, and another one-third are considered overweight. The gut microbiome is associated with the breakdown, absorption, and storage of carbohydrates, amino acids, and lipids, and with energy expenditure, ultimately influencing both body weight and body composition. Research has shown that individuals with normal body weight tend to have less dysbiosis than those who are obese. Early human studies showed that the Firmicutes-to-Bacteroidetes ratio is significantly higher in obese subjects, and that a higher amount of Firmicutes in a sample is associated with obesity development, while higher Bacteroidetes is associated with weight loss.¹

2. Eczema and Psoriasis

Although eczema (atopic dermatitis) is an allergic condition that can occur at any age, it is more common in children. The skin becomes inflamed, red, and itchy, particularly in bodily creases like behind the knees. To date, the most popular treatment is a prescription topical cream that will control the symptoms but does not address the root cause. Researchers recently discovered a relationship between the gut and the skin – a gut-skin axis. They found that eczema is likely related to an imbalance in the gut that affects the immune system. Sufferers of eczema tend to have higher proportions of Clostridia (including Clostridium difficile), Escherichia coli, and Staphylococcus aureus than do healthy controls, as well as lower numbers of healthy Bifidobacteria, Bacteroidetes, and Bacteroides.²

Unlike eczema, psoriasis appears more likely on the face, buttocks, and scalp. Studies have found that individuals with psoriasis are also more likely to suffer from inflammatory bowel disease. In terms of the microbiome, research shows that individuals with psoriatic lesions tend to have higher Firmicutes, Actinobacteria, and Corynebacterium kroppenstedtii. Both Staphylococci and Propionibacterium were present at lower levels, while Proteobacteria was present at higher levels in psoriasis than in healthy adults.³

3. IBS/IBD

Irritable bowel syndrome and inflammatory bowel disease are different GI conditions, and both, like most GI conditions, are linked to disruptions in the gut microbiota. We previously described the gut microbiome differences and also what was found in the Thorne-sponsored clinical trial of adults with IBS and their gut microbiomes. Like many other instances, GI conditions (gastritis, SIBO, and others) have a bi-directional effect on the gut microbiome; a condition can alter its composition or its composition can result in a GI condition.⁴

4. Parkinson’s Disease

Parkinson’s disease is a central nervous system disorder that affects the brain and causes unintended or uncomfortable movements, such as shaking, stiffness, and difficulty with balancing and coordination. Gastrointestinal symptoms and alterations of the enteric nervous system accompany the disease. Reviews on the gut microbiome’s involvement in Parkinson’s have found those who suffer from it tend to have higher abundances of the genera Lactobacillus, Akkermansia, and Bifidobacterium and lower volumes of bacteria belonging to the Lachnospiraceae family and the Faecalibacterium genus (both important short-chain fatty acids [SCFAs] producers), resulting in a pro-inflammatory gut status.⁵

5. Autoimmune Diseases

An autoimmune disease is one in which the immune system, by not recognizing the difference between your own cells and foreign cells, mistakenly attacks itself. This category of diseases includes type 1 diabetes, rheumatoid arthritis, lupus, celiac disease, multiple sclerosis, and alopecia, among others. Both genetic and environmental factors contribute to autoimmune conditions. Researchers hypothesize that the increasing incidence of autoimmune disease might be due to microbiome shifts caused by dietary changes and/or the widespread application of antibiotics. Although each autoimmune condition is slightly different, the research generally shows the microbes in the gut affect the balance of Th17 cells (cells that protect against invading microbes) and Tregs (specialized T cells that suppress the immune response and maintain homeostasis), influencing pro- and anti-inflammatory cytokine levels.⁶

6. Allergies

An allergic reaction is when the body perceives a normally harmless substance as a sensitivity when it comes in contact with skin, nose, eyes, respiratory tract, or gastrointestinal tract. The reaction releases histamine, which can cause the uncomfortable symptoms we associate with allergies. Alterations in gut bacterial levels or diversity of species are associated with the rise in food allergy incidence. Many studies showcase the relationship between development of allergies and early (infant) colonization of the gut microbiota. Children whose milk allergy dissipated with age had enriched Clostridia and Firmicutes after birth compared to children whose allergy to milk persisted. Similarly, low gut microbiota richness in early infancy and higher Enterobacteriaceae to Bacteroidaceae ratio (at age three months) was shown to be associated with food sensitivities at age one year. Intestinal dysbiosis in egg-allergic children is characterized by an increase in Streptococcaceae and Lachnospiraceae genera, and a decrease in Leuconostocaceae families compared to children without egg allergies. Although researchers are unable to pinpoint the ideal microbial composition to avoid food allergies, the science is evolving rapidly.⁷

7. Anxiety/Depression

Much like the gut-skin axis, the gut-brain axis is also a bi-directional communication pathway that influences your brain and mental well-being. Research shows that gut bacteria are responsible for producing beneficial neurotransmitters, such as serotonin, dopamine, and GABA, which play a major beneficial role in regulating feelings of anxiety, depression, and everyday mood. The science suggests it is essential for early colonization of infant microbiomes with Bifidobacterium and species from the Lactobacillus genus (both from breastmilk), and that these beneficial microbes be maintained through adulthood. They are key in producing GABA, an inhibitory regulator of various neural pathways.⁸ Thorne has partnered with Mayo Clinic for a succinct review that explains the role of the gut microbiome in mental health concerns.

8. Metabolic Syndrome/Diabetes Mellitus

Individuals with metabolic syndrome clinically exhibit high blood pressure, high blood sugar, excess weight, high triglycerides, and low levels of “good” HDL cholesterol, as well as low-grade inflammation and insulin resistance, putting them at risk for type 2 diabetes. Research shows there are many direct links to the way the body metabolizes nutrients and gut health. One connection is with the gut’s ability to produce short-chain fatty acids – the end products of microbial fermentation of dietary fibers. SCFAs like acetate, propionate, and butyrate help regulate fat and liver metabolism to maintain energy balance by regulating gut metabolism and appetite hormones. SCFAs also reduce low-grade inflammation by maintaining tight junctions in the gastrointestinal lining.⁹ As metabolic syndrome progresses to type 2 diabetes, a key bacterium to monitor is Akkermansia muciniphila. A decreased level of A. muciniphila is linked to impairment of insulin secretion and glucose homeostasis.¹⁰

9. Alzheimer’s Disease

A progressive disease that destroys memory and other mental functions, Alzheimer’s has been linked to gut dysbiosis only recently. Researchers demonstrated a correlation between imbalanced gut microbiota and the development of amyloid plaques in the brain (a clinical signal of Alzheimer’s progression).¹¹ Amyloid plaques contain lipopolysaccharides (LPS), large molecules located on the membrane of bacteria with pro-inflammatory properties that can leak from the gut. High levels of LPS, acetate, and valerate were found to be associated with large amyloid deposits, and high levels of butyrate were associated with less amyloid pathology.¹¹

10. Atherosclerosis

Atherosclerosis – the deposition of hardened plaque in arterial walls – obstructs blood flow, can loosen and cause a blockage, and can be ameliorated through diet, exercise, and lifestyle changes. (Read this cholesterol primer for more on lipids.) Therefore, it is not surprising there is a link to gut health. Research shows arterial plaque contains bacterial DNA – bacterial taxa that were also observed in the gut and oral mucosa of the same individuals.¹² There is a connection between bacterial infections and plaque formation, including Chlamydia pneumoniae, Porphyromonas gingivalis, Helicobacter pylori, and others.¹³

11. Infertility/Reproductive Problems

Many conditions are related to fertility in both men and women, including PCOS, endometriosis, and testicular dysfunction. What these conditions have in common is they present with an abnormal hormone profile. The gut microbiota can affect the endocrine system and key reproductive hormones that influence the capacity to conceive. For example, research shows the gut microbiome affects estrogen levels and vice versa. Microbes can secrete beta-glucuronidase, an important enzyme that metabolizes estrogen. Increased levels of beta-glucuronidase-producing bacteria can lead to too much estrogen and to diseases such as endometriosis and cancers (ovarian, breast, etc.). On the other hand, bacterial dysbiosis can also result in lower estrogen levels and lead to obesity, metabolic syndrome, cardiovascular disease, and cognitive decline.¹⁴

12. Nonalcoholic Fatty Liver Disease (NAFLD) and Nonalcoholic Steatohepatitis (NASH)

It is estimated that 24 percent of U.S. adults have NAFLD and more than six percent have NASH. NAFLD is characterized by fat build-up in the liver; NASH is when NAFLD progresses to inflammation and scarring. Studies of the gut-liver axis show correlations between the gut microbiome and various liver diseases, including NAFLD, autoimmune liver disease (AILD), and alcoholic liver disease. The gut microbiome in individuals with cirrhosis shows decreased bacterial diversity, increased immunostimulatory pathogens like Enterococcaceae (a toxin-releasing organism) and Staphylococcaceae, and a decline in potentially beneficial Firmicutes like Lachnospiraceae and Ruminococcaceae.¹⁵

What can you do?

Although this does seem complex, Thorne’s Gut Health Test makes it easy to understand your gut microbiome. Your results report every organism mentioned in this post and will help you better understand how you can change your diet, supplementation routine, and lifestyle to optimize your gut health and minimize dysbiosis.

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