Glossary - P


A remedy that encompasses all.

Parallel group study

Parallel group study also referred to as randomised controlled trial, is a type of clinical study design. These studies involve two groups of participants, randomly assigned to receive different treatments. In some cases, one group will be given a placebo and the other group will receive the actual treatment.

Pathogenic bacteria

Pathogenic bacteria, or pathogens, are harmful bacteria that cause disease or illness. Well-known pathogens include Salmonella or most types of E. coli.


Pepsin is one of the body's key digestive enzymes, produced and activated by cells in the stomach. Its fundamental role is to help break down proteins into their smaller form, known as peptides. 


Peristalsis refers to the wave-like contraction and relaxation of smooth muscle. In the digestive system these organised contractions propel ingested food through the Gastrointestinal tract. This passage through the GIT is very important. Poor digestion occurs when food moves too quickly, while food moving too slowly allows deposits of undigested food to ferment, leading to problems such as bloating. Without sufficient bulk (often due to a low fibre diet), normal peristalsis struggles to move the entire contents of the GIT along.


Phagocytes are a type of white blood cell which play a vital role in the functionality of the immune system. Phagocytes perform the specific role of ingesting and absorbing pathogens or toxins, and can also release enzymes to destroy them. Once a phagocyte has engulfed a pathogen, it can communicate to other immune cells, such as lymphocytes, to help identify the type of antibody needed to neutralise invading pathogens.


This is one of the categories used in the biological classification of organisms and is ranked below kingdom and above class. It is a scientific hierarchy used to help arrange similar types of organisms together. For example, members of the genus known as Lactobacilli belong to the Firmicutes phylum. 

Phytic acid

All plants contain phytic acid at varying levels to help protect them from predators. Unfortunately this form of self-defence may cause digestive problems in humans. Pulses such as lentils and beans have particularly high levels of phytates, which can be reduced by soaking them overnight in water. 

Pilot Study

A pilot study is a small study, experiment, or set of observations which are undertaken in advance of a planned large-scale project. It is used specifically to test aspects of the research design and to evaluate feasibility in advance of the project. This allows adjustments and improvements to be made prior to its start.

Pine Bark Extract

Pine Bark Extract is a derivative specifically extracted from bark of the pine tree, usually of the Pinus maritima. Pine Bark Extract is often classified as a superantioxidant, and is believed to have numerous benefits on the body including improved circulation, reduced period pain, as well as anti-ageing properties.

For further information, see antioxidants.

Placebo-controlled study

A placebo-controlled study is a clinical experiment in which the test subjects are split, usually, into two different control groups. One group will receive the medicine or supplement being trialled and the other will simply receive a placebo (a capsule, tablet, powder or liquid identical in appearance to the medicine or supplement being trialled but designed to have no measurable health effect). In most cases, placebos are used in blind trials where the control groups do not know if they are receiving the placebo or the real treatment.


Plasma is one of the main components of blood. 55% of blood volume is made up of plasma. Plasma itself contains a mix of proteins (Albumin, fibrinogen and immunoglobulins), salts and hormones.


Polyphenols are naturally occurring compounds, some of which are known to protect cells against the damaging effects of free radicals (therefore giving them antioxidant properties). They are broadly categorised into 4 mains groups; phenolic acids, stilbenes, lignans and flavanoids. Flavonoids are further classified into several groups. Flavanols, one of the group of flavonoids most abundantly found in fruit and vegetables, is made up of catechins and proanthocyanins, such as Grape Seed Extract.

Certain polyphenols are either specific to a particular food (e.g flavanones found in citrus fruit, resveratrol in red wine) and others are found in all plant foods (e.g quercetin is found in fruit, vegetables, cereals, legumes, tea & wine).

Research suggests that polyphenols, with their antioxidant properties, may play a role in the prevention of diseases, particularly relating to cardiovascular health and cancer prevention.


Pouchitis, with symptoms such as diarrhoea and abdominal pain, is an inflammation of the ileoanal pouch, a bowel pocket created to hold bowel movements in patients with ulcerative colitis who have had their large intestine or colon removed. Whilst antibiotics are often used as treatment for pouchitis, research shows that people with pouchitis have lower levels of beneficial bacteria in their system.


Prebiotics such as Fructooligosaccharides (FOS) can be found naturally in certain foods such as leeks and chicory root. Prebiotic fibres are a food source for probiotics to grow, multiply and survive in the gut; in particular stimulating growth of probiotics from the Bifidobacteria genus. For further detail into prebiotics, see: What are Prebiotics?


A premature, or preterm, baby is one that is born before 37 weeks of pregnancy.


Members of this gram-negative genus are closely related to bacterioides, and are commonly a cause of wound infections in cat and dog bites. In humans, they exist as opportunistic organisms which are implicated in periodontal disease and anaerobic (absence of oxygen) respiratory tract infections such as pneumonia.


Probiotics are microorganisms, usually bacteria, that have proven health benefits - for the digestive and immune systems in particular. Different probiotic strains have been shown to demonstrate different beneficial effects on the body. Although probiotics are commonly referred to as 'friendly bacteria', probiotics can be other microorganisms, for example the probiotic yeast, Saccharomyces boulardii.

For more information, see What are Probiotics?


This refers to anything that can promote inflammation. Cell death, histamine and pro-inflammatory cytokines could all promote an inflammatory response.

Prokaryotic cell

These are simple, single-celled organisms that do not have organelles or other internal membrane-bound structures. Critically they do not have a nucleus so only contain a single chromosome.


This is a preventative measure used to help protect against or avoid a disease or condition occurring. For example, probiotics can be taken prophylactically to prevent food poisoning when travelling to a high risk area.


Also known as ‘purple bacteria’, this term refers to a major phylum of gram-negative bacteria which include pathogens such as E. coli and Salmonella. 

Pseudomembranous Colitis

Pseudomembranous colitis is an infection of the colon commonly, but not exclusively, caused by an overgrowth of Clostridium difficile in the large intestine. An overgrowth of C. difficile is commonly attributed to the taking of antibiotics. Known symptoms of Pseudomembranous colitis include diarrhoea, abdominal pain and a severe inflammation of the inner lining of the colon.


Probiotic bacteria that either directly or indirectly influence the gut-brain axis and confer a benefit to mental health.