Bacteria that are beneficial or at least not harmful to the host, in contrast to pathogenic bacteria where the host derives no benefit and is actively harmed from the relationship. Roughly 100 trillion commensal bacteria live in the human gut. The term commensal comes from Latin and literally means “eating at the same table.”

An infectious disease caused by the novel coronavirus SARS-CoV-2. COVID-19, or coronavirus disease 2019, was first identified in Wuhan, China, in late 2019. The disease manifests primarily as a lower respiratory illness, but it can affect multiple organ systems, including the cardiovascular, neurological, gastrointestinal, and renal systems. Symptoms include fever, cough, fatigue, shortness of breath, and loss of smell and taste. Some infected persons, especially children, are asymptomatic. Severe complications of COVID-19 include pneumonia, sepsis, acute respiratory distress syndrome, kidney failure, multiple organ dysfunction syndrome, and cytokine storm. Treatments currently involve symptom management and supportive care. Mortality varies by country and region, but approximately 6 percent of people living in the United States who are diagnosed with COVID-19 expire.[1] 1

A broad category of small proteins (~5-20 kDa) that are important in cell signaling. Cytokines are short-lived proteins that are released by cells to regulate the function of other cells. Sources of cytokines include macrophages, B lymphocytes, mast cells, endothelial cells, fibroblasts, and various stromal cells. Types of cytokines include chemokines, interferons, interleukins, lymphokines, and tumor necrosis factor.

An unhealthy change in the normal bacterial ecology of a part of body, e.g., the intestines or the oral cavity.

A collective term for a group of conditions characterized by itchy or inflamed skin with a rash-like appearance. Seven types of eczema have been identified: atopic dermatitis, contact dermatitis, dyshidrotic eczema, nummular eczema, seborrheic dermatitis, and stasis dermatitis.

A molecule composed of carboxylic acid with a long hydrocarbon chain that is either saturated or unsaturated. Fatty acids are important components of cell membranes and are key sources of fuel because they yield large quantities of ATP when metabolized. Most cells can use either glucose or fatty acids for this purpose.

Flavonoid are widely distributed in plants, fulfilling many functions. Flavonoids have been shown to have a wide range of biological and pharmacological activities in animal, human, and in-vitro studies. Examples include anti-allergic, anti-inflammatory, antioxidant, antimicrobial, anti-cancer, and anti-diarrheal activities.

A group of signaling proteins made and released by host cells in response to the presence of several pathogens, such as viruses, bacteria, parasites, and tumor cells. Interferons are named for their ability to interfere with viral replication and are critical components of the body's innate immune response to viruses. SARS-CoV-2, the virus that causes COVID-19, impairs the body's interferon response.

An essential mineral present in many foods. Iron participates in many physiological functions and is a critical component of hemoglobin. Iron deficiency can cause anemia, fatigue, shortness of breath, and heart arrhythmias.

Lactate is thought to participate in a sort of "lactate shuttle" where, after being produced in muscle from exercise, it is transported in to tissues like the heart, and brain, where it is used as an energy source. Lactate is one of many molecules that falls under a loose group of molecules referred to as exerkines, a broad group of exercise-induced hormonal-like factors. Evidence suggests that lactate is the preferred fuel of the brain. Additionally, rodent studies suggest that lactate mediates some of the benefits of exercise on learning and memory via inducing neuronal brain-derived neurotrophic factor (BDNF) expression.^[1] In clinical studies, lactate shows promise as a treatment for inflammatory conditions including traumatic brain injury and as a means to deliver fuel to working muscles.

The collection of genomes of the microorganisms in a given niche. The human microbiome plays key roles in development, immunity, and nutrition. Microbiome dysfunction is associated with the pathology of several conditions, including obesity, depression, and autoimmune disorders such as type 1 diabetes, rheumatoid arthritis, muscular dystrophy, multiple sclerosis, and fibromyalgia.

A collective term for the community of commensal, symbiotic, and pathogenic microorganisms that live in a particular environment. The human body has multiple microbiotas, including those of the gut, skin, and urogenital regions.

A type of white blood cell, also known as a granulocyte. Neutrophils are the most abundant form of blood cell, comprising approximately 60 percent of total cells. They ingest, kill, and digest microbial pathogens, and are the first cells recruited to acute sites of injury. Neutrophils can infiltrate brain structures, driving inflammation and increasing the risk for neurodegenerative disorders, such as Parkinson's disease and Alzheimer's disease.

In general, anything that can produce disease. Typically, the term is used to describe an infectious agent such as a virus, bacterium, prion, fungus, or other microorganism.

Fatty acids that contain fewer than six carbons in their chemical structure. SCFAs are produced by the gut microbiota during the fermentation of dietary fiber. They provide energy to colonic cells and are crucial to gut health. In addition, SCFAs may play roles in the prevention and treatment of metabolic syndrome, inflammatory bowel disorders, and certain types of cancer. Some evidence suggests SCFAs can cross the blood-brain barrier to affect brain function. The principal SCFAs produced in the human gut are acetate, propionate, and butyrate.

A molecule that allows cells to perceive and correctly respond to their microenvironment, which enables normal cellular function, tissue repair, immunity, cognition, and more. Hormones and neurotransmitters are examples of signaling molecules. There are many types of signaling molecules, however, including cAMP, nitric oxide, estrogen, norepinephrine, and even reactive oxygen species (ROS).

An essential amino acid. Tryptophan plays key roles in the biosynthesis of proteins and is a precursor to several molecules with physiological significance, including melatonin, niacin, and the neurotransmitter serotonin. Inflammation causes tryptophan to be reallocated from serotonin synthesis to that of kynurenine, which then converts to the neurotoxin quinolinic acid, leading to depression. Dietary sources of tryptophan include most protein-based foods, such as meat, beans, or nuts.