At its simplest level nondigestible carbohydrate (NDCH) is fiber.
You've read all the experts and they all suggest eating plenty of it. NDCH is - they tell you - in things like cellulose, wheat bran, gum arabic, resistant maltodextrin, polydextrose, fructooligosaccharide, galactooligosaccharides, and RS!
What does all that mean?
Relax! I've done the research and below I've listed what each of these NDCH is and where you will find them if you want to increase your consumption of them.
The very first nondigestible carbohydrate that most of us come in contact with is our mother's breastmilk. Human milk has 100 times more HMO (a type of nondigestible fiber) in it than cow's milk.
But as we grown we need to find our non-digestable carbs from other sources. None will ever be quite so good as mother's milk which contains over 130 different oligosaccharides and glycoconjugates and proportionately contains 90% galacto-oligosaccharides and 10% fructo-oligosaccharides.
Let's look at these NDCH's suitable for adults one by one and you'll see that some of them are in natural foods and others are manufactured products.
Their role is to reach the large intestine undigested where they are then fermented by beneficial bacteria. As they do this we effectively "grow" our own population of probiotics.
The Food And Nutrition Board divides fiber into two types: Dietary Fiber and Functional Fiber. This is what they say.
"Dietary Fiber consists of nondigestible carbohydrates and lignin that are intrinsic and intact in plants. Functional Fiber consists of isolated, nondigestible carbohydrates that have beneficial physiological effects in humans."
Why would you want to consume nondigestible carbohydrate?
Apart from promoting regularity, their big plus is that they help to grown the good bacteria inside of your - particularly the Bifidobacterium.
This is likely to be the fiber (nondigestible carbohydrate) that the human body was most adapted to use back in our hunter/gather days. It is found in green plants. It is an insoluble fiber that is slowly fermented by the bacteria in your colon. It is, if you will, the "natural" prebiotic. Eat your greens, fruits and vegetables and you'll be getting plenty of this one.
You can buy this as a supplement but there really is no need. Just eat your vege!
Contains wheat bran
Wheat bran is the outer layer of wheat. It is usually removed during the milling process and is not present in white bread and cakes.
However you can buy it as a seperate product and sprinkle it on breakfast cereal or add to baking. Think bran muffins. Also added back to wholewheat breads.
Can be added to smoothies, mixed in casseroles and stews - can in fact be added to many dishes to boost their fibre content.
Found added to many breakfast cereals.
Contains Gum Arabic
This is the hard sap taken from 2 different species of the acacia tree; Acacia senegal and Acacia seyal. It is an edible gum (E414) and is safe to eat but is also used in many non-edible products.
It is a very common ingredient in softdrinks (including coca cola) where it increases the fizz and in things such as cake toppings and sweets from marshamllows to M&Ms.
Slows colonic fermentation, decreasing gas and bloating.
And despite its name most of the gum arabic nowadays come from Africa. There is some controversary surrounding its production and breaches of "fair trade".
Contains resistant maltodextrin
Also called RMD. It is produced from things such as corn, rice or potato starch by heat and enzymatic treatments so that digestable starch becomes resistant to digestion.
Is in products such as Fibersol and Pinefiber.
Maltodextrin can be made from wheat starch in which case it may contain wheat protein and gluten.
Maltodextrin (not the resistant kind) is used as a sweetener extensively in manufactured products. Some people are allergic to it.
Polydextrose (E1200) is a water soluble fibre synthesized from glucose and sorbitol.
Very common in soda drinks, candy, dessert mixes, cakes, breakfast cereals, gelatins, desserts and salad dressings.
Some people object to it as being one of new functional fibers rather than one found in foods.
As it contains only 1 kcal per gram it is able to help reduce calories for weight loss.
A study showed that intake of Polydextrose significantly improvemented bowel function (increased frequency and ease of defecation) and there where no reports of abdominal distention, cramps, or diarrhea.
Often referred to as FOS or Oligofructose. Inulin is a very similar compound. Found in foods such as chicory root, Jerusalem artichokes, dandelion greens, onions, garlic, asparagus, barley, tomato, bananas, wheat. Both bananas and wheat do not contain a lot but they are foods that we eat regularly and so can be a valuble source. Found in products such as Metamucil.
Although FOS or inulin is often in a food in both the raw and cooked state there is usually more in the raw version. For example, raw onions have 4.3g per 100 gram whilst cooked onions have 3.0g per 100g on average. But keep in mind how much you eat of most foods. Most of us eat far more cooked onion than raw onion so overall you would get more that way.
Good table of common foods in the American diet and how much they contain of Inulin and Oligofructose here.
Most FOS used in supplements in the USA has been refined from white cane sugar. For some people this makes it unacceptable.
Often referred to as GOS. Commercially they are synthesized from lactose which is a sugar found in milk. Often used as a low cal sweetener in yogurt, sweets, bread, and drinks.
Galactooligosaccharides have been shown to reduce the adherance of e coli bacteria in your intestinal tract.
The GOS in human breast milk has been shown to reduce the adherence of Campylobacter jejuni, e coli, Helicobacter pylori and other harmful bacteria.
Contains resistant starch
Often referred to as RS. Made from maize and corns and easy to use in baking and cooking
The "resistant" part of the name simmply meaning that it is resistant to being digested.
There are several different types of resistant starch: one type is found in green potatoes and bananas. As the banana ripes the starch changes and it is no longer resistant.
The resistant starch travels through your digestive tract until it gets to the large intestine. There, good bacteria turn it into short-chain fatty acids such as butyrate which just happen to be the prefered fuel of the cells of your colon.
So you can increase your level of non-digestible carbohydrate by eating plenty of greens, vegetables, fruits and wholemeal wheat products. You can then give it a greater boost by using some of the Funtional NDCHs in your cooking and baking. This all increases the level of fiber that you are taking each day thereby easing elimination and "growing" the good bacteria inside of you.