A
Natural substances found in some plants and mushrooms that help the body adapt to stress, improve stress resilience, and enhance mental or physical performance. Commonly used adaptogens include ashwagandha, reishi, schisandra, and ginseng 1.
An unproven theory suggesting chronic stress leads to adrenal hormone dysregulation, resulting in fatigue, brain fog, and poor sleep 2. Symptoms associated with adrenal fatigue are real and warrant serious attention.
A functional medicine treatment using herbs or pharmaceuticals to reduce bacterial, yeast, or parasitic overgrowth in the gut.
A condition where the immune system mistakenly attacks the body\u2019s own tissues. Examples include Hashimoto\u2019s, celiac disease, and rheumatoid arthritis.
B
Bifidobacterium (see Lacto-Bifido Probiotics)
A genus of bacteria native to the human gut that provides many health-promoting effects. Bifidobacteria are also well-studied probiotic supplements used to support digestion and immunity.
Protective barriers formed by bacteria and yeast that shield them from the immune system and treatment.
A common digestive symptom involving abdominal pressure or fullness, often linked to small intestinal bacterial overgrowth (SIBO), irritable bowel syndrome (IBS), or food sensitivities.
A subjective feeling of mental cloudiness, poor memory, or slowed thinking, often related to gut health, inflammation, or thyroid imbalance.
C
An excessive growth of Candida yeast in the gut or body, potentially causing fatigue, digestive issues, and brain fog.
A lab test that aims to evaluate gut bacteria, pathogens, digestion, inflammation, and immune markers. While these tests are popular, the science behind them is still developing. Split-sample testing has produced inconsistent results, and there\u2019s no established \u201cnormal\u201d reference range for many of the markers reported.
A hormone made by the adrenal glands that helps regulate energy, stress, and metabolism. Imbalances may contribute to fatigue or insomnia.
The active compound in the spice turmeric, which gives it its yellow color and is studied for its potent anti-inflammatory effects 3.
D
DHEA (Dehydroepiandrosterone)
A precursor hormone produced by the adrenal glands that helps make estrogen and testosterone.
The body’s natural process of eliminating toxins, often supported with dietary changes, liver support, and gut healing.
An imbalance between beneficial and harmful gut bacteria that may lead to symptoms including gas, bloating, fatigue, and inflammation.
E
A liquid diet of pre-digested nutrients originally designed as a medical food. The formula allows the gut to rest and reduces the impact of trigger foods, making it a popular protocol for gut conditions. Most often used as a treatment for inflammatory gut conditions like Crohn\u2019s disease 4. Research shows efficacy for reducing bacterial overgrowth, especially in small intestinal bacterial overgrowth (SIBO) 5.
A short-term protocol that removes common food triggers to identify intolerances or sensitivities.
A hormonal imbalance where estrogen is too high relative to progesterone, often contributing to mood changes, weight gain, and PMS.
F
Foods that have been naturally preserved and transformed by beneficial bacteria, yeast, or molds. During fermentation, these microbes break down sugars and starches into acids, gases, or alcohol, often producing probiotics that support gut health. Common examples include sauerkraut, kimchi, kefir, yogurt, miso, tempeh, and kombucha. While fermented foods can improve microbiome diversity and digestion, some individuals with gut imbalances (like SIBO or histamine intolerance) may need to introduce them slowly or avoid them temporarily.
The acronym that stands for fermentable oligosaccharides, disaccharides, monosaccharides, and polyols. FODMAPs are short-chain carbohydrates found in many foods that can ferment in the gut and trigger symptoms like bloating, distension, gas, constipation, and diarrhea. High FODMAP foods can worsen gut symptoms for some people, particularly people with irritable bowel syndrome (IBS) and small intestinal bacterial overgrowth (SIBO). Low-FODMAP diets are used during SIBO treatment.
A systems-based approach that investigates and treats the root causes of disease rather than symptoms alone.
G
A stool test using DNA technology to evaluate microbiome balance, infections, inflammation, and digestion.
An amino acid that supports gut lining integrity and healing. Glutamine is the primary fuel for enterocytes (gut cells), and supplemental glutamine is helpful in treating cases of increased intestinal permeability (leaky gut). Also called L-glutamine.
Types of proteins, including gliadin and glutenin, that are found in wheat, rye, and barley.
The balance and function of the digestive system, including digestion, nutrient absorption, immune activity, and the gut microbiome. Good gut health supports overall well-being, while imbalances can lead to issues like bloating, fatigue, and food sensitivities.
H
An autoimmune condition where the immune system attacks the thyroid, often leading to hypothyroidism.
A naturally occurring organic compound produced in your body, released by mast cells during an immune response. Histamine is also found in foods like wine, cheese, and aged meats. Some people are sensitive to histamine, a condition called histamine intolerance.
A bacterium that infects the stomach lining and is linked to ulcers, reflux, bloating, and nausea.
A condition where the thyroid gland underproduces hormones, leading to symptoms like fatigue, cold intolerance, constipation, hair loss, and weight gain.
I
IBS (Irritable Bowel Syndrome)
A functional gastrointestinal disorder characterized by bloating, abdominal discomfort, and altered bowel movements.
The body’s immune response to injury or imbalance. Acute inflammation is necessary for good health. Chronic inflammation underlies many functional and autoimmune conditions.
A state in which the body\u2019s cells stop responding efficiently to insulin, leading to high blood sugar and metabolic disease.
Increased Intestinal Permeability (Leaky Gut)
A condition where the cellular junctions of the gut lining become weakened and overly permeable, allowing toxins and food particles to enter the bloodstream. Also called gut barrier dysfunction and intestinal hyperpermeability.
IBD (Inflammatory Bowel Disease)
A group of conditions, including Crohn\u2019s disease and ulcerative colitis, characterized by chronic inflammation of the digestive tract.
J
A common symptom of body-wide inflammation, autoimmune disorders, or nutrient deficiencies. Often improves with diet and gut healing.
Extracting liquid from fruits and vegetables for nutrient concentration. Often used in detox protocols.
K
A fermented tea containing beneficial bacteria and yeast. May benefit gut health, but can worsen symptoms in some individuals.
A high-fat, very low-carb diet used in metabolic, neurological, or weight loss therapies.
A plant-based meal replacement shake made with protein, fiber, superfoods, adaptogens, digestive enzymes, and probiotics. It\u2019s often used for gut support, convenience nutrition, and meal simplification during elimination diets or resets. While marketed as a complete meal, users should verify tolerability with gut-sensitive conditions.
L
Common probiotic strains (Lactobacillus and Bifidobacterium) that help restore gut balance and support immunity.
Leaky Gut (see Increased Intestinal Permeability)
A lay term for increased intestinal permeability, believed to contribute to autoimmune issues and chronic inflammation 6.
A type of protein found in many foods that binds to sugars. Lectins are found in grains, fruits, vegetables, meat, and fish, and some foods contain higher amounts of lectins than others.
Occurs when the brain doesn\u2019t respond properly to leptin, a hormone that regulates fullness and fat storage.
Low Stomach Acid (Hypochlorhydria)
A condition where insufficient hydrochloric acid (stomach acid) impairs digestion and nutrient absorption.
M
MCAS (Mast Cell Activation Syndrome)
A condition where the immune system overreacts to common things like food, stress, strong odors, bug bites, medications, illness, and infection. Leads to increased histamine and allergy-type reactions that can cause inflammation and symptoms throughout the body.
A biochemical process involved in gene expression, detoxification, and neurotransmitter production.
The collection of trillions of microorganisms (bacteria, yeasts, viruses, archaea, fungi, parasites, and protists) that live in the gastrointestinal tract. The bulk of the microbiome lives in the colon (large intestine). The microbiome influences digestion, immunity, metabolism, and mental health.
Organelles that are found in nearly every cell of the body and are influenced by diet and lifestyle. Mitochondria produce ATP (energy), regulate calcium, and produce reactive oxygen species. Dysfunctional mitochondria are linked to several chronic diseases 7.
The muscular movement of the digestive tract that helps move food and waste. Impaired motility may lead to SIBO.
An IV infusion of nutrients used to support energy, immune health, and stress recovery.
N
A coenzyme found in every cell that plays a key role in energy production, cellular repair, and metabolism. NAD levels naturally decline with age and stress, which may impact energy, brain function, and detoxification. NAD therapy (often via IV or supplements) is used in functional medicine to support mitochondrial health and overall vitality.
An opioid antagonist drug used at low doses (low-dose naltrexone, LDN) to help regulate immune function and inflammation, particularly in autoimmune conditions 8.
A condition where the body reacts to gluten without celiac disease. Symptoms may include fatigue, brain fog, and digestive discomfort.
Nutritional compounds or supplements that offer therapeutic health benefits.
O
Healthy fats that support brain, heart, and immune function, and help reduce inflammation.
A urine test used to evaluate nutrient levels, gut health, mitochondrial function, and detoxification.
Plant compounds that may trigger symptoms like joint pain or kidney stones in sensitive individuals.
P
Parasympathetic nervous system
Part of the nervous system that relaxes your body and supports digestion.
Short chains of amino acids that promote tissue repair, anti-aging, and hormone regulation.
Sores in the stomach lining, often caused by H. pylori infection or NSAID use. Can be treated with gut-healing and antimicrobial support.
Compounds found in all plant foods with antioxidant and anti-inflammatory properties. Certain plant foods, such as green tea, berries, herbs, and spices, contain very high levels of polyphenols. Polyphenols help increase good gut bacteria 9.
Non-living microorganisms, vitamins, or the products of microorganisms, like butyrate, that provide health benefits such as lowering gut inflammation and supporting the gut lining 10.
Fibers that selectively feed beneficial gut bacteria. Found in foods like garlic, onions, beans, asparagus, artichoke, and bananas.
Live microorganisms that, when consumed in adequate amounts, provide health benefits, such as improving gut balance and supporting immune and digestive health 11.
Acid-reducing medications that may impair digestion if used long-term 12. Often prescribed for reflux and GERD.
A natural protocol designed to eliminate parasitic organisms from the digestive tract. Typically includes antiparasitic herbs like black walnut, wormwood, and clove, along with binders and digestive support. Used in cases of known or suspected parasitic infections, often after travel or with chronic digestive symptoms.
Q
A plant flavonoid with antioxidant and anti-inflammatory properties. Commonly used in allergy and immune support.
R
A condition where stomach acid backs up into the esophagus. Often linked to poor gut motility and weakened muscle tone in the lower esophageal sphincter 13. Also called gastroesophageal reflux disease (GERD).
An inactive form of thyroid hormone that can block active T3. Can rise during stress or chronic illness 14.
Root-Cause Medicine
A functional health philosophy focused on identifying and resolving the underlying contributors to disease.
S
A probiotic yeast that helps manage diarrhea, rebalance the gut, and reduce inflammation 15.
An adaptogenic berry used in Traditional Chinese Medicine to support liver detoxification, stress resilience, and gut-liver axis health. It may also have antioxidant and anti-inflammatory properties beneficial for gut lining repair and immune modulation 16.
Short-Chain Fatty Acids (SCFAs)
Compounds produced by gut bacteria that reduce inflammation and support gut health. Butyrate is one example of a well-studied SCFA 17.
SIBO (Small Intestinal Bacterial Overgrowth)
A condition where excess bacteria grow in the small intestine, causing bloating, gas, nutrient malabsorption, and bowel irregularities 18.
Durable probiotic strains (like Bacillus) that survive stomach acid and support both the small and large intestines 19.
Mild thyroid dysfunction where TSH is elevated, but T3 and T4 remain in the normal range. It can cause symptoms, but most often it does not progress to overt hypothyroidism.
Part of the nervous system that regulates blood pressure, physical endurance, sweating, and stress. Also called the \u201cfight or flight\u201d nervous system.
T
T3 is the active thyroid hormone, while T4 is converted into T3 for use in metabolism and energy regulation.
A lab test evaluating TSH, Free T3, Free T4, and antibodies to assess thyroid function and autoimmunity.
Tirzepatide
A GLP-1 and GIP receptor agonist used to support blood sugar regulation and weight loss.
A probiotic strategy combining Lacto-Bifido strains, Saccharomyces boulardii, and spore-based probiotics.
U
An inflammatory bowel disease that causes ulcers and chronic inflammation in the colon.
Ubiquinol (CoQ10)
An antioxidant that supports cellular energy and cardiovascular health. Often used in mitochondrial and statin-related therapies.
V
The main nerve connecting the brain and gut. Plays a central role in digestion, relaxation, and the regulation of inflammation.
When vitamin D levels are too low. Vitamin D deficiency affects immunity, mood, and bone health. Often treated with vitamin D supplementation.
Fat stored around internal organs. Linked to inflammation and higher disease risk.
W
A diagnostic test used to detect infections like Lyme disease by measuring antibodies in the blood.
Non-celiac reactions to wheat, causing symptoms like bloating, fatigue, and brain fog.
X
Compounds that mimic estrogen and can disrupt or influence hormone balance. May be synthetic (like bisphenol A) or natural (like genistein found in soy). Natural xenoestrogens are also called phytoestrogens 20.
A sugar alcohol used as a low-calorie sweetener. May cause digestive upset in some individuals.
Y
An excess of yeast organisms in the gut (such as Candida), often triggered by stress and gut dysbiosis.
Z
A trace mineral essential for immunity, wound healing, and gut lining integrity. Zinc is naturally found in foods like shellfish, red meat, pumpkin seeds, cashews, beans, and dairy.
A protein that regulates intestinal permeability. Elevated levels may indicate leaky gut and an increased risk of inflammation 21.