Glossary - M


Malabsorption refers to an inability to fully absorb the nutrients from food. 


The first few stools or faeces of a newborn infant are known as meconium. Unlike adult stools, meconium is almost odourless and is often dark olive green in colour and sticky like tar.


Melaena refers to dark "tarry" faeces that are associated with bleeding in the upper gastrointestinal tract, or the swallowing of blood. The dark colour is a consequence of the haemoglobin in the blood being altered by digestive secretions and intestinal bacteria. Probiotics are not recommended for those experiencing melaena. For further information on this please read the FAQ on when not to take probiotics.

Meta analysis

This is an examination of data from a number of independent studies of the same subject in order to decide what the overall trends may be.


The term metagenome refers to the genetic material which is present in a sample taken from the environment, and is made up of the genomes (genetic information) of an array of individual microorganisms.

Methane-producing bacteria

Also known as methanogens, these types of organisms produce methane as a by-product of their metabolism, which among other things, contributes to flatulence production in humans. They thrive in low oxygen environments such as the human gut and have also been found in extreme conditions such as deep glaciers and in hot desert soil.


A microscopic organism, such as a bacterium, fungus or virus.


A microbiome encompasses the entirety of microbes in a defined habitat, including all of their genetic make-up and their environmental interactions. For example; a human microbiome (all of the microbes that we share our body with) includes approximately 100 trillion microbes, outnumbering our own cells by 10 to 1.

Find out more about the microbiome.


'Microbiota' refers to the microorganisms (both probiotic and pathogenic) residing in the gastrointestinal tract. An imbalance in the microbiota is known as dysbiosis.

Find out more about the microbiota.


Microflora generally refers to the microorganisms (including both good and bad bacteria) that reside in the digestive tract. As the term 'flora' refers to plants, however, the term microbiota is now considered to be more correct than microflora.


This new area of research looks at the effect that host sex, and the various male and female sex hormones, have on our commensal gut flora. Early studies in to the 'microgenderome' reveal that sex does have a direct impact on the composition of our gut flora, which may provide researchers with a useful insight in to the complexities of many autoimmune conditions which have a strong 'sex bias' in the future.


Microvilli are microscopic hair-like protrusions on the tips of cells, that in the digestive system play an important role in the secretion of digestive enzymes and absorption of properly digested nutrients. Malabsorption problems can develop when these structures are damaged, as seen with coeliac disease. 


The international standard way of measuring blood glucose levels are in terms of a molar concentration, measured in mmol/L.


A mucin is a glycosylated (where a carbohydrate molecule attaches to the protein) protein which is produced by the epithelial tissues. Their main characteristic is to be able to form gels, so play an important role in gel-like secretions which may have a lubricating, cell-signalling or protective function.


Mucosa, also known as the mucous membrane, refers to the moist lining of internal, hollow organs such as the mouth and gastrointestinal tract.


Murine refers to the family of rodents belonging to the Muridae family. These rodents include rats and mice.


The term 'mycobiome' refers to the fungal populations in a given environment. Studies have demonstrated the existence of diverse fungal colonies throughout the human body, and suggest their importance in both health and disease. There are many different genera of fungi, including: Candida, Fusarium, Cladosporium and Aureobasidium.