Glossary - F


Fibre is the word given to non-digestible carbohydrates derived from plant sources in our diet. Fibre is often described as ‘soluble fibre’ or ‘insoluble fibre’. Soluble fibre includes pectin and beta-glucans, from fruit and oats respectively. Insoluble fibre is found in whole grains and nuts. In nature, fibre rich foods tend to include both types of fibre. Resistant starch, such as that found in grains, legumes, bananas and cooked-and-cooled potatoes is also classed as fibre.


Firmicutes are the largest family of bacteria found in the human microbiome. They are anaerobic, so do not need oxygen to survive. The Lactobacilli and Clostridia species both belong to this family of bacteria.

Free radicals

Free radicals or reactive oxygen species (ROS) are molecules that are produced as part of natural bodily processes, such as energy production, as well as being a by-product of environmental and lifestyle factors, such as smoking and air pollution. A free radical is an unstable and highly reactive molecule and can, therefore, do damage to cells in the body. As a result, in high numbers they are thought to contribute to a range of diseases including cardiovascular disease, cancer as well as the ageing process. Free radical damage can be minimised by the use of antioxidants.

Friendly bacteria

Friendly bacteria is another name for probiotics (also known as good or beneficial bacteria). Friendly bacteria are defined as any bacteria that are beneficial to the body and enhance health.

FOS (fructooligosaccharides)

Fructooligosaccharides (FOS) are one of the most well-known prebiotics, which are carbohydrates that provide food for the probiotic bacteria and thus help them to grow and colonise the intestines. FOS is naturally occurring in foods such as chicory root. It has a slightly sweet taste and can be used as a natural sweetener instead of sugar. As humans, we can’t digest or absorb FOS and it passes through our digestive tract to the large intestine where it acts as a food source for probiotics.


A fungus is a member of a large group of spore-forming organisms that range from microorganisms such as yeasts and moulds to the more familiar mushroom. They play a vital role in the decomposition of organic matter and the nutrient cycle.

Additions to our Probiotics Glossary

If you come across a term you feel should be within our Probiotics Glossary, please do not hesitate to reach out to us and we will endeavour to research and add them. Email us at: [email protected]/uk

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