The Prebiotic Benefits of Oligosaccharides

Jerusalem artichokes on a cutting board

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Sandwiched between simple sugars (monosaccharides) and starches (polysaccharides) are oligosaccharides. Oligosaccharides are a type of carbohydrate that acts as a prebiotic, providing food for the good bacteria in the gut. You can get oligosaccharides in your diet by eating foods that are naturally rich in them, or that have had oligosaccharides added.

What Are Oligosaccharides?

Oligosaccharides are a type of carbohydrate formed when three to 10 simple sugars are linked together. The human digestive system has a difficult time breaking down many of these carbohydrates. About 90% of them bypass digestion in the small intestine, eventually reaching the colon.

There, oligosaccharides take on a new role—that of a prebiotic. Prebiotics are a food source for the healthy bacteria in your gut. Fructooligosaccharides and galactooligosaccharides are the two main types of oligosaccharides that act as prebiotics.

Some people follow a low-FODMAP diet—the O in FODMAP stands for oligosaccharides. While oligosaccharides are beneficial for most people, those with IBS or Crohn's disease may experience digestive symptoms when eating foods with oligosaccharides.

Prebiotics are not to be confused with probiotics. While both terms relate to gut health, pre- and probiotics have different roles, health benefits, and sources; probiotics are the "good" bacteria in the gut, and prebiotics are a source of food for those bacteria.

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

Foods with Oligosaccharides

Small amounts of oligosaccharides occur naturally in many plants, but chicory root and Jerusalem artichokes (the root of a member of the sunflower family) have the most oligosaccharides. They are also found 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.

Non-Plant-Based Sources of Oligosaccharides

The most common oligosaccharide food additives are inulin and oligofructose. Protein bars, for example, feature inulin. Other brands also include inulin, though it's listed on the label as "chicory root fiber" because it can be derived from chicory.

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.

Oligosaccharides are also important for babies’ digestive health. They are present in breast milk and are added to infant formula.

Why Oligosaccharides Aren't Always Labeled As 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 response to a citizen's petition for the inclusion of synthetic carbohydrates on food labels under the product's dietary fiber content, the FDA proposed listing added oligosaccharides and other isolated or synthetic non-digestible carbohydrates (NDCs) to the labels. The change is still pending.

Benefits of Oligosaccharides

Oligosaccharides help promote the growth of healthy gut microflora. From there, bacteria that feed on fermentable carbohydrates produce many beneficial substances, including short-chain fatty acids (SCFAs) and certain B vitamins.

As the gut bacteria break down oligosaccharides, they are producing SCFAs. Some early evidence suggests the bacteria could promote absorption of certain minerals, including calcium and magnesium, that escape the small intestine during digestion.

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

While research is ongoing, SCFAs likely provide many benefits both 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:

  • Lower cholesterol
  • Lower triglycerides
  • Improved insulin sensitivity and glucose metabolism
  • Improved immune system function
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