Inulin: a Beneficial Carbohydrate / You Asked for It
2003 May 05
By Hunter, Beatrice Trum
Food for Thought
Inulin, a fiber-like carbohydrate, occurs in some 36,000 plants. Vegetables that contain inulin
include onions, garlic, leek, asparagus, and Jerusalem artichokes. Among fruits, bananas and
raisins are sources. Grains that contain inulin include wheat, rye, and barley. For commercial
purposes, the main extract is from chicory root.
Inulin was identified as early as 1804 by a German scientist who named the substance. Later
research demonstrated that inulin offered several nutritional and health benefits. Participants at a
conference sponsored by the National Institutes of Health in 1998 discussed inulin's role in
calcium uptake, its improvement of fat metabolism, its ability to bestow benefits for
gastrointestinal health, and its positive effect on the immune system.
Inulin is non-digestible, and functions as a soluble dietary fiber. It is low in calories, but
contributes a few calories due to some fermentation in the colon. It acts as a prebiotic, stimulating
the growth of beneficial bacteria.
Although certain fibers in the diet are known to bind specific nutrients in the digestive tract and
prevent their absorption, inulin does just the opposite. It stimulates the absorption of certain
minerals, especially calcium and magnesium. In rat studies, inulin helped to increase absorption
of these minerals in the large intestine; it also increased calcium uptake into the bone tissue. This
resulted in improved bone-mineral density and bone trabecular structure (the supporting strands
of connective tissue projecting into an organ and constituting part of the organ's framework). It
was found that an uptake of 8 grams of inulin daily could increase calcium absorption by 20%.
This is good news for many people who are attempting to meet their calcium requirements.
Inulin affects blood-lipid metabolism. It is thought that the effect is caused by the fermentation of
this non-digestible carbohydrate into fatty acids that are absorbed and metabolized by the liver.
Inulin is neither hydrolyzed nor absorbed in the upper part of the gastrointestinal tract. Instead,
inulin is fermented in the colon, where it produces short-chain fatty acids that favor healthy colon-
cell growth, and inhibit tumor growth that can lead to diseases such as colon cancer. By lowering
the pH in the large intestine, the fatty acids create an environment inhospitable to pathogens such
as Escherichia coli and strains of Salmonella. Inulin acts as a receptor analog that interferes with
surface adhesions of bacterial pathogens attaching to the brush border of the intestine.
One mechanism by which these special carbohydrates may protect humans from colon cancer
involves butyric acid, which stimulates healthy colon cell growth and suppresses cancerous cell
production. Inulin stimulates the growth of one or more beneficial bacteria that normally reside in
the colon, such as bifidobacteria.
Inulin's beneficial effects in the colon are important, as some 100,000 new cases of colon cancer
are diagnosed each year in the United States.
Several national surveys show that most Americans eat only about half of the officially
recommended 25 grams of fibers daily. Many nutritionists believe that adults should be eating
eight to 10 fruits and vegetables daily. This is twice as many as the modest official goal of "five a
day," which is not being met. Fruit and vegetable intake, along with whole grains, provide dietary
fiber. Inulin, with its fiber-like quality, can make its contribution to the total intake. Like fibers,
inulin decreases fecal transit time and prevents constipation.
Inulin, as a food constituent, is tolerated by diabetics. It does not lead to a rise in blood glucose,
nor does it stimulate insulin secretion.
Inulin is classified as a polysaccharide (many sugars) and is composed of a chain of fructose
units with a terminal glucose unit. Because of this structure, it is considered to be a medium-
chain-- length fructooligosaccharide.
Increasingly, nondigestible oligosaccharides (NDOs) such as inulin are being added to food and
beverage products. At present, the average daily ingestion of NDOs is below the upper safety
level of 15 grams per day. At high levels, they are laxative.
Because onions contain inulin, a bowl of onion soup may contain up to 10 grams of inulin.
Historically, Australian aborigines consumed as many as 35 grams of inulin daily by consuming
murnong, an inulin-containing plant.
Recent research, sponsored by the California Raisin Marketing Board, shows that raisins are a
good inulin source. According to independent laboratory analysis, a standard 1/4 cup serving of
raisins contains 1 1/2 grams of inulin. To date, no official recommended daily intake of inulin has
been established. However, according to U.S. Department of Agriculture surveys, the amount of
inulin in the serving of 1/4 cup of raisins is equivalent to about 58% of the average American's
daily inulin intake.
In recent years, inulin extracted from chicory root has become a popular substance for use in
processed foods. The means of extraction is similar to that of extracting sugar from sugar beets.
The yield is about 95% inulin, and the remainder consists of mono-, di-, and oligosaccharides
(naturally occurring sugars). Due to the presence of these sugars, inulin gives foods a slightly
sweet taste, but adds no color. One manufacturer produces a patented form of inulin from which
all of the sugars have been removed.
Inulin can be used as a texturizer because of its ability to thicken into a particle gel described as
creamy and fat-like. Low in calories, inulin is used to replace some of the fat and sugar in food
products. Also, it gives "body" to beverages, improves the texture and "mouthfeel" of low-fat dairy
products, gives viscosity and mouthfeel to sauces, helps bind water in processed meats, helps
aerate no-fat icings and whipped toppings, and provides a creamier mouthfeel in potato products.
Inulin applications have extended to baked goods, salad dressings, cereals, desserts,
confections, mayonnaises, and margarines.
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