The Benefits of Oligosaccharides and Prebiotics

Jerusalem Artichokes on a cutting board
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You may not be familiar with them, but sandwiched between simple sugars (monosaccharides) and starches (polysaccharides) is another group of carbohydrates that play an important role in nutrition.

You've likely seen ingredients like inulin and oligofructose listed on food labels and may have heard phrases like “prebiotic fiber. " Here's what these terms mean and how they relate to your diet.

Oligosaccharides

Oligosaccharides are a type of carbohydrate formed when three to 10 simple sugars are linked together. Small amounts occur naturally in many plants, but chicory root (from which most commercial inulin is extracted) and so-called Jerusalem artichokes (the root of a member of the sunflower family) have the most oligosaccharides.

The carbohydrate is also found in varying amounts in onions (including leeks and garlic), legumes, wheat, asparagus, jicama, and other plant foods.

North Americans get about 1 to 3 grams of oligosaccharides naturally in their diets each day. Europeans get slightly more: around 3 to 10 grams.

Most oligosaccharides have a mildly sweet taste. Other characteristics, such as the mouthfeel they lend to food, have drawn the interest of the food industry. Many manufacturers are exploring oligosaccharides as a partial substitute for fats and sugars, as well as a way to improve a product's texture.

Due to these attributes, the amount of synthetically-produced oligosaccharides present in the food we eat is on the rise.

The nutrition community has also become more interested in oligosaccharides, though for a completely different reason: The human digestive system has a difficult time breaking down many of these carbohydrates. About 90 percent bypass digestion in the small intestine, eventually reaching the colon. Here, oligosaccharides take on a new role—that of a prebiotic.

Prebiotics

Prebiotic is a fairly recently coined term—not to be confused with probiotics. While both terms relate to gut health, pre- and probiotics have different roles, health benefits, and sources.

Prebiotics are components in the large intestine that support the growth of certain kinds of bacteria in the colon.

At first, oligosaccharides were believed to be the main form prebiotics, but it turns out bacteria in the colon also feed on resistant starch and fermentable fiber. We now understand there's an entirely different (and crucial) digestive process happening in the colon that influences the rest of the body.

Are Oligosaccharides Fiber?

While oligosaccharides do fall under the categories of both soluble fiber and fermentable fiber, they are not currently included under dietary fiber on food labels in the United States. One exception is inulin from chicory root, which may be listed as fiber on nutrition labels.

In March of 2019, in response to a citizen's petition for inclusion of synthetic carbohydrates on food labels under the product's dietary fiber content, the FDA proposed changes to current guidelines that would include added oligosaccharides and other isolated or synthetic non-digestible carbohydrates (NDCs) as part of a food's dietary fiber content.

Health Benefits

Bacteria that feed on fermentable carbohydrates produce many beneficial substances, including short-chain fatty acids (SCFAs) and certain B-vitamins.

While the research is still new, SCFAs likely provide many benefits, both locally in the colon as well as in the rest of the body. Specifically, butyrate may protect colon tissue from damage caused by conditions like colon cancer and ulcerative colitis.

Other possible benefits of SCFAs include:

Interestingly, different oligosaccharides tend to produce different SCFAs—a good reason to eat a variety of oligosaccharide-containing foods.

Some early evidence suggests the bacteria could promote absorption of certain minerals, including calcium and magnesium, that escape the small intestine during digestion.

Added Inulin

In addition to plant-based sources, food additives can also be a source of oligosaccharides. The most common are inulin and oligofructose.

Quest Bars, for example, feature inulin in their line of protein bars. Other brands also include inulin, though it's listed on the label as "chicory root fiber."

Inulin is also available as an over-the-counter vitamin supplement you can purchase in health food stores or online.

You can also get the prebiotic benefits of oligosaccharides by adding more fermentable fiber, including resistant starch, to your diet.

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