Glossary - I

Immune system

The human immune system is a complex system of cells, processes and biological structures that protects the body from pathogenic microorganisms. The mucosal lining of the gut, which is maintained by probiotics, plays an important part in this system and is considered the front line against disease.

Healthcare practitioners can find out more about probiotics and the immune system on our sister site, Probiotic Professionals.


Immunomodulatory is where something such as a supplement, medication or chemical is capable of changing or modifying the immune response.

In vitro

Commonly known as ‘test tube’ experiments, these types of studies usually isolate components of an organism in an artificial laboratory environment so that certain factors can be more easily controlled. An example of this is in vitro fertilisation, whereby the egg is fertilised by sperm in equipment outside the body.

In vivo

In vivo experiments involve complete living organisms such as animal studies and clinical trials involving humans. In vitro experiments are another type of research.

Increased intestinal permeability

This occurs when the tissue lining the gut wall becomes damaged and allows certain substances such as toxins, microbes and undigested food to leak through the gut wall and into the blood stream. A healthy gastrointestinal system usually allows certain substances to pass through the gut wall such as water, vitamins and minerals but provides a barrier against other substances passing through. Increased intestinal permeability plays a key role in leaky gut syndrome. 

Healthcare professionals can find out more about leaky gut over in our sister site, Probiotic Professionals.


Indigestion (or dyspepsia) generally describes pain or discomfort in the chest or abdomen, that usually develops during or shortly after eating or drinking. 


Inflammation is part of a complex bodily response to infection or injury. This could be a mechanical, chemical, viral, bacterial, or biologic cause of damage. The body reacts with reddening, swelling, heat, pain and loss of function. The term inflammation is usually used with a specific area of the body in mind but is now often used to refer to the general increase in an ‘inflammatory state’ in the body. Inflammation is a natural and healthy response, however, persistent, systemic inflammation can lead to illness.

Inflammatory Bowel Disease (IBD)

Inflammatory Bowel Disease (IBD) refers to both ulcerative colitis and Crohn's disease; both of which cause intestinal inflammation and symptoms such as abdominal pain, vomiting and diarrhoea.

For a unique probiotic with anti-inflammatory properties, see Saccharomyces boulardii.

Healthcare professionals can read more about probiotics and IBD on our sister site, Probiotic Professionals.


Insulinemia is the term used to describe high levels of circulating insulin in the blood. Insulin is a hormone produced by the pancreas, and its role is to help the liver, muscle and fat tissue to take up glucose from the blood and convert it to glycogen that is stored in the liver and muscles.  A diet high in sugar may cause insulin resistance, when the cells of the body become less sensitive to insulin, therefore increased quantities of insulin are found in the blood. Insulin resistance is seen as a risk factor for Type 2 Diabetes and heart disease.  


Interleukins are a family of cytokines which are a group of naturally occurring proteins that are responsible for signaling between cells. Interleukins may regulate cell growth but they are particularly important in stimulating immune responses, such as inflammation.

Intestinal failure

This occurs when a large portion of the small intestine does not function normally or is not present. It usually occurs due to surgical removal or infant’s can also be born with abnormal intestines. Symptoms of intestinal failure include diarrhoea, weight loss, bloating and vomiting and if left untreated, digestion can be compromised and may lead to dehydration, malnutrition and small intestinal bacterial overgrowth.


Inulin is a prebiotic, and a natural polysaccharide (several simple sugars linked together) occurring in the roots and tubers of certain plants such as chicory.

Irritable Bowel Syndrome (IBS)

Irritable Bowel Syndrome (IBS) is a functional disorder of the gastrointestinal tract characterised by varying symptoms such as bloating, abdominal pain or discomfort; accompanied by diarrhoea or constipation or alternation between the two.

For further reading, see: Which probiotics are for IBS?

Ischemic heart disease

Ischemic heart disease is a condition of recurring chest pain. This happens when part of the heart is not receiving enough blood. Ischemic heart disease may also called coronary heart disease. Ischemic heart disease usually develops when cholesterol particles in the blood start to collect in the arteries and stick to the artery wall. Eventually these deposits of cholesterol becomes hard and form plaques which may narrow the artery. This can then decrease blood flow and therefore the amount of oxygen which is supplied to the heart muscle. Signs and symptoms of ischemic heart disease can either develop slowly or quickly. Some people have no symptoms at all, but more often than not people experience severe chest pain (angina) and a shortness of breath. This can of course pose a risk of a heart attack.