A MICROSCOPIC VIEW OF THIS CHAPTER
• Prebiotics are carbohydrates, food for probiotics.
• Prebiotics support growth and activity of healthy intestinal microflora.
• Bifidobacteria are simulated by prebiotics, called the bifodogenic effect.
• Prebiotics lower blood cholesterol and triglyceride levels.
• Prebiotics may have positive effects on calcium absorption and cancer prevention.
Despite how similar in spelling prebiotics is to probiotics, the two are very different. Only probiotics are living organisms. Prebiotics are actually carbohydrates. Prebiotics are carbohydrates that the body cannot digest, but probiotics can! Since the body cannot digest prebiotics, they are left unaltered as they travel through the intestinal tract and reach the colon ready to be used by the probiotics living there, particularly Bifidobacteria. Prebiotics are the preferred food source for probiotics. Prebiotics are nondigestible oligosaccharides (a short-chain sugar molecule) that help promote the growth and activity of probiotics.
What is an example of a prebiotic? Inulin, beta-glucan, pectin and resistant starch are all carbodhydrates that act as prebiotics in the human intestinal tract. Inulin is found in onions, chichory root and dandelions; oligosaccharides are found in artichokes, leeks and asparagus; beta-glucan is found in seaweed, oats and barley; pectin is found in apples and apricots; and resistant starch is found in raw bananas, potatoes and beans. Research has shown that eating prebiotics can improve the growth of lactic bacteria in your intestines, especially Bifidobacteria. Prebiotics also help to inhibit the growth of a variety of undersirable microorganisms.
Prebiotics are non-digestible food ingredients that may beneficially affect the host. Prebiotics selectively stimulate the growth and activity of one or a limited number of good bacteria in the colon and thus improve the host’s health.
Prebiotics are naturally present in our daily diets; however, the Western diet does not include sufficient prebiotics to properly support our probiotic flora. Our diet is about two to three times too low in prebiotics. It has been estimated that North Americans eat about 1 to 4 grams of prebiotics (e.g., inulin and other oligosaccharides) daily, while Europeans consume 3 to 10 grams per day. Humans should consume at least 4 grams of prebiotics each day. We eat too many processed foods, sugary treats and meats.
WHAT FOODS CONTAIN PREBIOTICS?
Flax, barley, oats and other whole grains are great sources of prebiotics. Greens, such as spinach, kale and dandelion leafs, are also a good source of prebiotics. Prebiotics can be found in lentils, including chickpeas and kidney beans. Even delicious favorites like berries and bananas are natural sources of prebiotics.
Since prebiotics are not digested by the body, they have a reduced caloric value. They do not lead to a rise in your blood glucose level or stimulate the secretion of insulin. What they do offer is fiber. Prebiotics are dietary fiber. As such, they have many positive effects on your intestines. Fiber helps to increase stool frequency, particularly in people suffering from constipation. Prebiotics also decrease fecal pH. This drop in pH helps prevent the production of harmful (putrefactive) substances by bad microbes in the colon. By this mechanism, prebiotics may have a cancer preventative effect. These harmful chemicals can lead to damage of colon cell DNA, which can, in turn, lead to cancer.
Do you need another reason to include prebiotics in your diet? Researchers have found that the consumption of prebiotics decreases the level of bad fats in your blood. In a research trial, the blood levels of triglycerides and cholesterol decreased with prebiotic use in people with high cholesterol levels.
Do you need fiber for your bones? Yes. Prebiotics have been shown in animal studies to have positive effects on calcium absorption. Prebiotics (inulin and oligofructose) may contribute to the prevention of osteoporosis. Eat more grains, greens, beans and berries as these prebiotic foods may offer a whole array of healthy benefits.
You might not find raw, green bananas appealing for dinner, but your microflora do. Raw, green bananas are a great source of resistant starch. Ripe bananas do not have the same amount of resistant starch. Resistant starch is an area of prebiotics that is gaining interest within the research world. Preliminary results suggest that resistant starch may increase the ability of probiotics to survive through the stomach. This means a larger number of probiotics can make it safely to their preferred site (small or large intestine) when prebiotics are in your diet. Resistant starch has a bulking capacity that may modify stomach pH and dilute the bile acid level in the small intestine. The ability of resistant starch to help probiotics survive the way down to the small and large intestine, added to its ability to beneficially stimulate the growth of microbes in your colon, has this prebiotic high on the up-and-coming supplement list.
What is the Difference Between Dietary Fiber and Prebiotics?
Both are non-digestible fiber. Prebiotics selectively promote the growth of colonic microbes. Prebiotics are dietary fiber; however, dietary fiber does not promote the growth of probiotics.
POPULAR PREBIOTICS
The most popular prebiotics are short chain fructooligosaccharides, more simply referred to as scFOS or FOS. Inulin is a type of FOS. The only difference between FOS and inulin is the number of chains in their chemical structure. Inulin and FOS are commercially available in foods and supplements. Inulin and FOS are synthesized from the sugar of beets and extracted from chicory root, respectively. By the way, chicory root is the root of the Belgian endive plant.
FOS is thought to be one of the best prebiotics. This is because other prebiotics (inulin and other oligosaccharides such as oligofructose) have to be converted by the human body before they can be used by the probiotics. FOS does not need to be converted. Prebiotics requiring metabolism are considered to be less effective than FOS. FOS is ready to offer its healthy benefits the instant it is consumed.
How do prebiotics work? In essence, the fundamental concept is the same for prebiotics as for probiotics. Prebiotics improve your health by beneficially affecting the intestinal microflora. In other words, prebiotics improve the makeup of the intestinal flora so that you stay healthy. Prebiotics support good microbes and inhibit the bad. The use of prebiotics alone can actually change the makeup and activity of the intestinal microflora.
The probiotic family, Bifidobacteria, are the common target for prebiotics. Why is this? Oligosaccharides are the preferred food source of Bifidobacteria. As such, prebiotics are sometimes referred to as having a bifidogenic factor, as they support the growth and colonization of Bifidobacteria. Please note that prebiotics may sometimes be referred to as “fermentable substrates.” This is because Bifidobacteria break down prebiotics with a process called fermentation to create energy.
Bifidogenic Effect
A product that stimulates, or claims to stimulate, Bifidobacteria is said to have a bifidogenic effect on the intestinal flora. Inulin, FOS and other prebiotics are known to have a bifidogenic effect in humans.
SYNBIOTICS
Researchers are looking at the effect of combining probiotics and prebiotics in what is called a synbiotic. Synbiotics, both probiotics and prebiotics together, are thought to produce more beneficial health effects than either on their own. This may be because prebiotics promote the growth of existing probiotics in the colon and improve the survival and growth of newly added probiotic strains. Prebiotics are the perfect, supportive partner for probiotics.
The European Union is sponsoring a project called SYNCAN that is looking into possible cancer-protective effects of synbiotics. The project was sparked by animal models that have shown that synbiotics dramatically reduce the development of cancer. The research says that synbiotics are more powerful than their prebiotic or probiotic components alone. Results from the SYNCAN project are promising. A human trial from the project found that a combination of inulin, Lactobacillus rhamnosus and Bifidobacterium lactis reduced the risk of colon cancer. As more results from SYNCAN are released, it will likely spark an increase in symbiotic products on the market.
Combining probiotics with prebiotics has already been welcomed by the food industry. In Europe, there are many dairy drinks and yogurt manufacturers combining both in products such as Aktifit (Emmi, Switzerland), Probioplus (Migros, Switzerland) and Fyos (Nutricia, Belgium), to name a few. Watch for more research in this area, particularly studies that identify which probiotic strains and prebiotic combinations are most effective. This is an exciting new area for prebiotics.
As prebiotics are so easily manufactured and are a part of a well-known food group (fiber), the general public is very accepting of prebiotic food products. Keep your eyes open for new food products that have added FOS, inulin or other prebiotics. Check out supermarket shelves for breads, cereals, fruit bars and perhaps soon even ice creams containing prebiotics.
SUMMARY
Prebiotics are carbohydrates that the human body cannot digest. When prebiotics are consumed in foods such as berries, beans, greens and grains, these carbohydrates reach the colon unaltered. There they are fermented by resident probiotics, Bifidobacteria. Prebiotics support the growth and health of probiotics. A prebiotic is capable of enhancing probiotic health and inhibiting the growth of bad microbes. Ultimately, prebiotics improve your health. Prebiotics lower blood cholesterol and triglyceride levels as well as having positive effects on calcium absorption and cancer prevention. The effect of probiotics can be enhanced when taken with prebiotics, a combination described as a symbiotic.
