Non-starch polysaccharides (NSPs) is the name of a category of chemicals found naturally in plants.
Non-starch polysaccharides (NSPs) are also known collectively as:
- dietary fibre (British English spelling)
- dietary fiber (American English spelling), and
- roughage (older term in wide colloquial use).
When to say "non-starch polysaccharides" and when to say "dietary fibre" (or equivalent):
Although these expressions refer to the same chemicals, some textbooks use them inter-changeably.
In general, 'dietary fibre' is used when describing and discussing NSPs in the diet, e.g. their functions and benefits and how they are processed by the human digestive system. 'Non-starch polysaccharides' are usually referred to when describing and explaining the chemistry, and therefore also the chemical reactions of NSPs. Obviously these areas are closely related because the digestive process includes chemical digestion e.g. due to the actions of acids, enzymes and bile.
- The page about dietary fibre mentions types of dietary fibre, the functions and benefits of dietary fibre and sources of dietary fibre with examples of high fibre foods and low fibre foods.
- This page about non-starch polysaccharides explains the general chemical structure of NSPs as compared with e.g. monosaccharides and disaccharides. It also lists examples of specific NSPs.
Polysaccharides compared with other carbohydrates:
As explained on the page about types of sugar (monosaccharides and disaccharides), there are 4 general categories of carbohydrates which can be listed in increasing size and complexity as:
The table above helps to explain the "polysaccharide" part of the term non-starch polysaccharides.
Definition of polysaccharide:
Polysaccharides are carbohydrates (i.e. organic chemicals that consist mainly of the elements carbon, hydrogen and oxygen) whose molecules take the form of long chains of monosaccharides (i.e. simple sugars) all joined together.
Although the general properties of polysaccharides include insolubility in cold water, no taste, and indigestible to humans, polysaccharides do play an important role in the human digestive system - as described on the page about dietary fibre.
Main types of polysaccharides:
There are many types of polysaccharides found in plant materials commonly included in human diets.
Important examples include:
In terms of their chemical composition and properties, non-starch polysaccharides are:
compounds that can be classified within the categories of the above table except for (i.e. excluding) starches.
Starch is the most common carbohydrate in the human diet. It is one type of polysaccharide. There are many different starches. Their sizes and shapes are characteristic of the plant that produced them, e.g. potatoes, bananas, beans (e.g. lentils, peas and chickpeas), barley, breadfruit, oats, oca, chestnuts, water chestnuts, wheat, yams, corn (maize) and rice. In all cases pure starch is a white, tasteless and odourless powder that is insoluble in cold water or alcohol. Starch is not readily digested by humans but it is more easily digested after it has been cooked in the presence of water e.g. in bread, pancakes, noodles, pasta and porridge.
Glycogen has a similar composition to that of starch. An important difference is that it is made (from glucose) by animals rather than by plants. Although small amounts of glycogen are stored in the body as an energy reserve it is insignificant in terms of humans dietary intake because glycogen stored in animal tissue breaks back down to glucose after an animal's physical death.
Non-starch polysaccharides therefore include cellulose (which forms the bulky structure of many plants) and pectins (which come from e.g. the stones of many fruits).
Examples of non-starch polysaccharides:
This list of compounds classed as non-starch polysaccarides (NSP)s is not complete but includes examples of common NSPs.
and some other carbohydrates with β-glycosidic linkages.
Some sources also include certain oligosaccharides as 'types of non-starch polysaccharides'. That is understandable because oligosaccharides consist of molecules whose structure is more than two monosaccharide molecules joined together. However, oligosaccharides are increasingly classified separately from polysaccharides so their inclusion in lists of 'examples of NSPs' might cause confusion.