Oligosaccharides vs Polysaccharides: Understanding the Differences

Oligosaccharides are short-chain carbohydrates found naturally in legumes, onions, garlic, and wheat. They're poorly absorbed in the small intestine, with much of their breakdown occurring due to bacterial fermentation by your gut microbes.

In contrast, polysaccharides are long-chain carbohydrates, often comprising hundreds or thousands of linked sugar residues. They have different properties from oligosaccharides and can serve as energy storage (as in starch and glycogen) or structural support (as in cellulose).

While there's a lot of fearmongering about them in the media, the truth is that carbohydrates are an important part of our diet, providing energy, fiber, and essential nutrients like B vitamins, iron, and magnesium. 

Interested in learning more about oligosaccharides vs. polysaccharides? Read on for the lowdown on their unique properties, food sources, health benefits, and the biological processes they influence.

Oligosaccharides vs Polysaccharides: Complex Carbohydrates at a Glance

In the human body, there are many types of building blocks. When we talk about protein, the individual building blocks are called amino acids, but the building blocks of carbohydrates are called monosaccharides. Glucose and fructose are two types of monosaccharides, and many carbohydrates are made up of multiple monosaccharides joined together. 

When two glucose molecules react, chemical bonds result from a dehydration reaction. This is because each glucose molecule has several hydroxyl groups, each consisting of an oxygen atom bonded to a hydrogen atom. When two glucose molecules connect, an -OH (hydroxyl group) from one glucose and an -H from the other combine to form a water molecule (H2O). The remaining oxygen forms a glycosidic bond between the two glucose molecules. This bond holds the two glucose residues together.

Before reviewing an oligosaccharide vs polysaccharide in detail, you may find it helpful to compare their main characteristics side-by-side

What Are Oligosaccharides?

Oligosaccharides are a type of carbohydrate made up of between 3 and 10 monosaccharides linked together by glycosidic linkages. While they're considered complex carbohydrates, they're less complex than polysaccharides such as starch.

Common types of oligosaccharides include fructo-oligosaccharides (FOS), which are chains of fructose sugars. Fructans are a type of FOS. Another common type of oligosaccharide is galacto-oligosaccharides (GOS), which are chains of galactose molecules. Raffinose is a type of GOS. 

Humans lack the enzymes needed to fully digest oligosaccharides, which results in them reaching the large intestine intact. However, this doesn't diminish their potential benefits to human health. Oligosaccharides serve as food for your gut microbiome (the community of bacteria, yeasts, fungi, viruses, and more inhabiting your digestive tract), making them an important component of maintaining a healthy gut.

Oligosaccharides occur naturally in many foods. GOS are common in legumes (like lentils, chickpeas, and kidney beans), while fructans are common in foods like wheat, onions, and garlic. Human breast milk also contains oligosaccharides known as human milk oligosaccharides, which play a critical role in infant gut health and immune system development. 

What Are Oligosaccharides?

Oligosaccharides are a type of carbohydrate composed of multiple monosaccharides (usually 3 to 10) linked by glycosidic bonds. While they're considered complex carbohydrates, they're less complex than polysaccharides such as starch. They're typically water-soluble, which is why draining and rinsing oligosaccharide-rich foods like beans, chickpeas, and lentils can help reduce the overall oligosaccharide content.

Oligosaccharide Structure

Chain length is a useful way to distinguish between different types of oligosaccharides, but other factors, such as the types of monosaccharides, bond types, and branching patterns, can also influence their chemical properties and behavior in the digestive system.

Structural differences, such as branching, can influence how easily digestive enzymes break down the oligosaccharide. While some oligosaccharide bonds are readily broken down by enzymes in the digestive tract, others resist human digestive enzymes and travel intact to the large intestine, where your gut bacteria ferment them. This is one reason different oligosaccharides can have extremely different effects on digestion, gas production, and the gut microbiome. 

Common Types of Oligosaccharides

Common types of oligosaccharides include fructo-oligosaccharides (FOS), which are chains of fructose sugars. Fructans are a type of FOS; inulin and chicory root are common sources. Another common type of oligosaccharide is galacto-oligosaccharide (GOS), which consists of chains of galactose molecules. Raffinose is a type of GOS. 

Humans lack the enzymes needed to fully digest many oligosaccharides, so they reach the large intestine intact. However, this doesn't diminish their potential benefits to human health. Oligosaccharides serve as food for your gut microbiome (the community of bacteria, yeasts, fungi, viruses, and more that inhabit your digestive tract), making them an important component in maintaining a healthy gut.

Where Are Oligosaccharides Found? 

Oligosaccharides occur naturally in many foods. GOS are common in legumes (such as lentils, chickpeas, and kidney beans), while fructans are common in foods such as wheat, onions, and garlic. Human breast milk also contains oligosaccharides known as human milk oligosaccharides, which play a critical role in infant gut health and immune system development. 

Health Implications of Oligosaccharides

Oligosaccharides offer many potential health benefits and have high nutritional value, but they can also cause digestive discomfort in some individuals. 

One of the significant health benefits of oligosaccharides is their role as prebiotics. Prebiotics are compounds that feed your beneficial gut bacteria, such as Bifidobacteria and Lactobacilli. This is important because a well-balanced gut microbiome supports digestion, immune function, and overall well-being.

Oligosaccharides support gut health, in part, through fermentation by gut bacteria in the colon. This produces metabolic byproducts called short-chain fatty acids (SCFAs), which nourish colon cells and may help reduce inflammation. Overall, SCFAs contribute to a healthy gut environment and may lower your risk of developing colorectal diseases like inflammatory bowel disease (IBD) and colorectal cancer. 

Oligosaccharides also support the immune system, partly by reducing harmful bacteria growth. Since an overabundance of harmful bacteria can weaken the gut barrier, preventing their growth can help maintain its integrity, a key component of a healthy immune system. The human milk oligosaccharides in human breast milk help develop a baby's immune system.

Finally, oligosaccharides may have metabolic benefits. Some studies in animals suggest that they can help regulate blood sugar levels. Plus, a recent study in humans with overweight and obesity found that eating oligosaccharides was associated with significant weight loss. This may be due to their slow digestion rate, which can contribute to feelings of satiety, making it easier to reduce overall calorie intake.

Can Oligosaccharides Cause Digestive Symptoms? 

Oligosaccharides can cause digestive symptoms in certain people, such as those with IBS. This is because many oligosaccharides (such as fructans and GOS) are FODMAPs. 

FODMAP stands for Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols. Since they're poorly absorbed in the small intestine and instead get fermented by the gut bacteria, FODMAPs can cause excess gas, bloating, and changes in bowel movements in susceptible individuals with FODMAP intolerance, such as those with irritable bowel syndrome (IBS).

What Are Polysaccharides?

Polysaccharides are complex carbohydrates made up of long chains of monosaccharides joined together by glycosidic linkages. These complex molecules serve several important functions, including cell signaling, energy storage, and structural support. Their specific physicochemical properties depend on which sugars they're made of, how those sugars are joined, and whether there is a branch point (or several).

Polysaccharide Structure

When it comes to structure, polysaccharides are made up of more than 10 monosaccharides joined by glycosidic linkages, though they often number in the hundreds or thousands. 

They can be linear (straight chains) or more complex, branched molecules. Whether or not they're made of straight or branched chains affects their digestibility and function.

There are two main types of linkages in polysaccharides. The first are called alpha-glycosidic linkages. These bonds are found in important polysaccharides like starch and glycogen and are easily digested by human enzymes.

The second type of linkage is called beta-glycosidic bonds. They're found in polysaccharides like cellulose (found in plant cell walls). While human enzymes cannot break down beta-glycosidic bonds into simple sugars, these compounds are important for structural support and serve as a source of dietary fiber.

Common Types of Polysaccharides

There are many types of polysaccharides, which can be classified by their functions in living organisms. 

Starch is a storage polysaccharide found in plant foods such as potatoes, grains, and legumes. There are two primary forms of starch—amylose (a linear polysaccharide composed of glucose residues) and amylopectin (a branched polysaccharide). The glycosidic linkages in amylose and amylopectin are digestible by humans and provide a long-lasting energy source, highlighting their biological importance. 

In contrast, glycogen is a highly branched polysaccharide composed of glucose molecules, stored in the liver and muscles of animals. It's broken down into glucose molecules to provide a quick burst of energy when the glucose available from recent meals has run out.

Structural polysaccharides include cellulose, a key component of plant cell walls that is indigestible by humans. However, cellulose acts as dietary fiber and supports gut health by promoting regular bowel movements and feeding your good gut bacteria.

Health Implications of Polysaccharides

Like oligosaccharides, polysaccharides are highly nutritious and play an important role in human health. They provide energy, digestive benefits, and structural support. 

One of the main health benefits of polysaccharides is sustained energy release. Storage polysaccharides like starch provide a steady supply of energy. These complex carbohydrates, like whole grains, legumes, and starchy vegetables, help maintain stable energy levels compared to refined carbs. This is because whole grains contain more fiber than refined carbs, which slows digestion and the release of glucose into the bloodstream, preventing blood sugar spikes.

Another key benefit of polysaccharides is their effect on digestive health. Dietary fibers like cellulose, hemicellulose, and pectin help promote regular bowel movements in people with constipation. Prebiotic polysaccharides like resistant starch (a type of starch that resists digestion in the small intestine and acts like fiber to promote gut health and support blood sugar control) feed your good gut bacteria, promoting a healthy gut microbiome. 

Soluble fiber, such as beta-glucans and pectin, also helps regulate blood sugar and cholesterol levels. These types of fiber have high viscosity and form a gel-like substance in the gut, slowing glucose absorption and improving blood sugar control. Soluble fiber-rich polysaccharides like beta-glucan also help lower LDL (bad) cholesterol by reducing the absorption of cholesterol and bile acids (which contain cholesterol) in the gut. Finally, clinical trials have demonstrated that beta-glucans may help modulate the immune response.

Key Differences Between Oligosaccharides and Polysaccharides

Oligosaccharides and polysaccharides are both carbohydrates, but they differ in several key aspects. The table below highlights their main differences.

Comparison of Oligosaccharides and Polysaccharides

Structure and Complexity

Oligosaccharides are relatively short carbohydrates composed of a small number (typically 3 to 10) of linked sugar units, whereas polysaccharides are much larger and often contain hundreds or even thousands of linked monosaccharides.

However, oligosaccharides and polysaccharides are not distinguished solely by chain length. They're also classified based on the types of sugars present (for example, glucose or fructose), the types of bonds connecting them, and whether the molecule is linear (straight) or branched. These properties all affect how they behave in the body, which is why simply looking at chain length doesn't always tell the whole story.

Digestion and Absorption 

Oligosaccharides play a vital role as prebiotics (food for your good gut microbes), while polysaccharides serve energy storage and structural roles and promote regular digestion. Despite their different nutritional properties, both play an important role in human health.

It's important to eat a variety of food products containing oligosaccharides and polysaccharides. Here are some food sources of both types of carbohydrates.

Digestion & Absorption

While oligosaccharides and polysaccharides are both carbohydrates made of multiple sugar units joined together, differences in their size and structure mean they are digested differently.

Many oligosaccharides (such as fructans and GOS) are not fully broken down by human digestive enzymes. Instead, they pass into the colon mostly intact, where gut bacteria ferment them. The fermentation process produces gases (such as hydrogen and carbon dioxide) and metabolites, including short-chain fatty acids (SCFAs). For people with a sensitive digestive tract (such as people with IBS), the gas produced as a byproduct of oligosaccharide fermentation can be extremely painful, leading to abdominal discomfort, bloating, and distention.

In contrast, the digestibility of polysaccharides varies widely depending on the length, structure (branched or unbranched), and types of bonds holding them together. Starch and glycogen (the storage forms of glucose, a monosaccharide, in the human body) contain chemical bonds that human digestive enzymes can break down, allowing their glucose units to be absorbed and used as energy.

However, other polysaccharides, such as cellulose and certain types of resistant starch, resist digestion in the small intestine and instead function as dietary fiber. Some of these fibers (such as resistant starch) are fermented by the gut bacteria, while others (such as cellulose) pass through the digestive tract largely unchanged. 

Physiological Role

Because their structures and digestibility differ, oligosaccharides and polysaccharides serve different functions in the body. 

When we talk about oligosaccharides, we often discuss them in relation to the gut microbiome, since many act as prebiotics that feed it. But oligosaccharides also have roles beyond digestion, including cell recognition and signaling. Human milk oligosaccharides (HMOS), for example, are an important component of human breast milk that helps shape an infant's microbiome and supports immune system development.

Polysaccharides have an even broader range of roles. Some, such as starch and glycogen, primarily store energy. Others, such as cellulose, provide structural support. Many types of polysaccharides also serve as dietary fiber and can influence stool bulk, water retention, fermentation, and bowel regularity. Certain types of polysaccharides have water-binding and gelling properties that affect both digestion and food texture.

Impact on Health

Certain oligosaccharides, such as fructans and GOS, may support a healthy gut microbiome because they are readily fermented in the colon. However, that same fermentability is what can also make them symptom triggers for people with IBS who are sensitive to FODMAPs. 

Polysaccharides such as starch can provide a quick burst of energy, while soluble fiber-rich polysaccharides may support regular bowel movements, stool consistency, satiety, blood sugar regulation, and microbial fermentation. In contrast, insoluble fiber-rich polysaccharides add bulk to stool and mechanically stimulate the intestines, helping move waste along smoothly.

The key takeaway? Neither oligosaccharides nor polysaccharides have a single effect on health. Their impact depends largely on their size, structure, amount consumed, and an individual's digestive tolerance. 

Common Examples of Oligosaccharides

Tips for incorporating oligosaccharides into your diet:

• Start slowly: Oligosaccharides, especially those found in legumes, wheat, onion, and garlic, can cause gastrointestinal distress when eaten in large portions. Start with a small portion and gradually increase your intake to a comfortable level.

• Eat canned and rinsed chickpeas and lentils: The canning process removes some oligosaccharides, so the final products retain less GOS. This may make you more likely to tolerate the GOS in canned beans and lentils.

• Use digestive enzymes: Digestive enzymes break down oligosaccharides (GOS and fructans) and lactose (the naturally occurring sugar found in dairy) as soon as they're added to your food. These enzymes may reduce the digestive side effects of eating oligosaccharides by breaking them down before they reach your large intestine. 

Common Examples of Polysaccharides

Tips for incorporating polysaccharides into your diet:

• Choose whole grains: Whole grains like brown rice, quinoa, whole wheat, barley, and oats are digested more slowly than refined grains, which reduces their impact on blood sugar levels and provides lasting energy.

• Increase your intake of resistant starch: Eat cooled and reheated potatoes, rice, or pasta to support gut health and reduce blood sugar spikes.

• Enjoy a variety of fruits and vegetables: To increase your intake of fibrous polysaccharides like cellulose, eat a variety of different fruits and vegetables (if possible, leave the skin on, as the skin contains high amounts of fiber).

Oligosaccharides, FODMAPs, and Digestive Enzymes

Certain oligosaccharides, such as the GOS found in beans or the fructans found in garlic, onions, and wheat, have prebiotic properties and can support the beneficial microbes living in your colon. At the same time, their high fermentability can trigger digestive symptoms such as gas, bloating, and abdominal discomfort in people who are sensitive to FODMAPs.

This is especially relevant to people with IBS who may be following a low FODMAP diet to manage their IBS symptoms, since fructan and GOS are two of the main carbohydrate groups restricted during the elimination phase. However, the goal of the low FODMAP diet is not to restrict these foods forever. The reintroduction and personalization (maintenance) phases are designed to help you determine which high FODMAP foods—and in what amounts—you can tolerate.

For some people who find that high-fructan foods or GOS-rich meals trigger symptoms, digestive enzymes can help increase dietary flexibility. In particular, enzymes that target specific FODMAPs can help break them down before they reach the colon, thereby reducing gas production.

Choosing the Right Carbohydrates and How FODZYME Can Help

Both oligosaccharides and polysaccharides have essential roles in a balanced diet and overall well-being. While polysaccharides offer sustained energy release, oligosaccharides act as prebiotics, nourishing your good gut microbes. However, some people struggle to digest certain oligosaccharides (like GOS and fructans), leading to uncomfortable symptoms like gas, bloating, abdominal discomfort, and changes in bowel movements. This is particularly common in those with IBS or FODMAP sensitivities.

That's where FODZYME comes in. FODZYME breaks down FODMAPs—fructan, GOS, lactose—into more digestible carbohydrates, so you can enjoy garlic, onion, bread, beans, and dairy—without the aftermath.

If you want to support your gut while enjoying a variety of nutritious foods, check out FODZYME here.

Oligosaccharides vs Polysaccharides FAQ

What’s the Main Difference Between Oligosaccharides and Polysaccharides? 

The main difference between oligosaccharides and polysaccharides is their size. While oligosaccharides are short-chain carbohydrates typically consisting of 3-10 monosaccharide units, polysaccharides are long-chain carbohydrates that may consist of hundreds or thousands of monosaccharide units.

Are Oligosaccharides or Polysaccharides FODMAPs? 

Not all oligosaccharides are FODMAPs, as not all oligosaccharides are rapidly fermented by your gut microbes. Polysaccharides are generally not classified as FODMAPs because they're long-chain carbohydrates that do not get fermented by your gut microbes.

Can FODZYME Help With Oligosaccharides? 

FODZYME is a digestive enzyme blend that targets two types of oligosaccharides: fructans and GOS. If foods like onions, garlic, wheat, or legumes cause digestive symptoms, taking a digestive enzyme supplement to break down oligosaccharides before they reach your large intestine and are fermented by your gut bacteria may reduce gas, bloating, and abdominal discomfort.

Oligosaccharides vs Polysaccharides: Which Is Better for You? 

Since oligosaccharides and polysaccharides differ in structure and function, neither is "better" than the other. Polysaccharides, such as fiber-rich carbohydrates, can support digestion and provide energy, while certain oligosaccharides have beneficial prebiotic effects. However, certain oligosaccharides, such as fructans and GOS, may cause digestive symptoms in people who are sensitive to FODMAPs. Each person has different needs, so it's important to choose both oligosaccharide- and polysaccharide-rich foods that work for you.