Which food has oligosaccharides for better gut health?

December 8, 2025 •

4 min read

According to research, oligosaccharides are nondigestible carbohydrates that feed beneficial bacteria in the gut, promoting a healthy microbiome. For those seeking to improve their digestive system and overall health, understanding which food has oligosaccharides is key to building a prebiotic-rich diet.

Quick Summary

Oligosaccharides are prebiotic fibers naturally found in various plant-based foods, including legumes, vegetables, and whole grains. They are not digested by the human body but are fermented by gut bacteria, contributing to a balanced gut microbiome. Common sources include beans, onions, garlic, wheat, and asparagus.

Key Points

Diverse Sources: Oligosaccharides are found in a wide variety of foods, including legumes, vegetables, fruits, and grains.
Prebiotic Power: They function as prebiotics, meaning they feed beneficial gut bacteria like Bifidobacterium and Lactobacillus.
Gut Health Booster: Fermentation of oligosaccharides by gut bacteria produces short-chain fatty acids (SCFAs), which support gut health and immunity.
FODMAP Consideration: As a type of FODMAP, oligosaccharides can cause digestive symptoms like gas and bloating in sensitive individuals, such as those with IBS.
Cooking Affects Content: Processing methods like soaking and cooking can reduce the oligosaccharide content in foods like legumes, potentially improving digestibility.
Key Examples: Common examples include fructans from onions and wheat, and galacto-oligosaccharides (GOS) from beans and lentils.
Essential for Gut Microbiome: Incorporating these foods supports a diverse and healthy gut microbiome, which is vital for overall health and wellness.

Understanding Oligosaccharides

Oligosaccharides are a type of prebiotic fiber, which are complex carbohydrates made of short chains of sugar units. Unlike other carbs, the human body cannot fully digest oligosaccharides in the small intestine. Instead, they travel to the large intestine where they are fermented by beneficial bacteria, such as Bifidobacterium and Lactobacillus. This fermentation process supports the growth of these 'good' bacteria, which in turn produce short-chain fatty acids (SCFAs), providing numerous health benefits.

Types of Oligosaccharides

There are several types of oligosaccharides, with some of the most well-known being:

Fructans (FOS and Inulin): These are chains of fructose molecules found in many common vegetables. Inulin is a longer-chain fructan, often added to processed foods as a fiber supplement.
Galacto-oligosaccharides (GOS): These are chains of galactose molecules and are prevalent in legumes and milk-based products.
Raffinose and Stachyose: These belong to the raffinose family of oligosaccharides (RFOs) and are composed of galactose, glucose, and fructose.

Legumes: A Powerhouse of Oligosaccharides

Legumes are one of the richest sources of galacto-oligosaccharides (GOS), which can help improve gut health and digestion. However, because humans lack the enzyme to break down these compounds, they are also associated with gas and bloating in some individuals.

Lentils: Both red and green lentils contain significant amounts of GOS.
Chickpeas: A popular source of GOS, found in hummus and other dishes.
Beans: Varieties like kidney, black, navy, and lima beans are all high in oligosaccharides.
Soybeans: These contain both GOS and other oligosaccharides and are used to make various products, including soy milk and soft tofu.

Vegetables Rich in Oligosaccharides

Beyond legumes, a variety of vegetables are excellent sources of oligosaccharides, especially fructans.

Onions and Garlic: These are arguably the most common sources of fructans and are widely used in cooking.
Leeks and Scallions: Belonging to the Allium family, these vegetables are also rich in fructans.
Asparagus: This vegetable contains a good amount of inulin.
Jerusalem Artichoke: Also known as a sunchoke, this is one of the highest sources of inulin.
Chicory Root: This is the primary commercial source for extracting inulin used in food manufacturing.
Brussels Sprouts and Broccoli: These cruciferous vegetables contain raffinose and other oligosaccharides.

Grains, Fruits, and Other Sources

Many common grains and certain fruits also provide a natural source of oligosaccharides.

Wheat and Rye: These are major sources of fructans, which some individuals may find difficult to digest, leading to non-celiac gluten sensitivity symptoms.
Barley: This grain contains a mix of fiber, including fructans.
Bananas: Less ripe bananas are a source of resistant starch and some fructans.
Honey: This natural sweetener can also contain small amounts of oligosaccharides.

Comparison of Common Oligosaccharide Sources


Food Type	Primary Oligosaccharide Type	Examples	Notes
Legumes	Galacto-oligosaccharides (GOS) and Raffinose	Lentils, chickpeas, black beans, soybeans	Can cause gas in sensitive individuals
Allium Vegetables	Fructans (FOS)	Onions, garlic, leeks, scallions	Common cooking staples rich in prebiotic fiber
Root Vegetables	Fructans (Inulin)	Chicory root, Jerusalem artichoke, dandelion greens	Exceptionally high in inulin
Grains	Fructans and Raffinose	Wheat, rye, barley	Fructans in wheat can cause discomfort for some
Cruciferous Vegetables	Raffinose	Broccoli, Brussels sprouts, cabbage	Good sources, but can contribute to gas
Fruits	Fructans (FOS) and others	Bananas (less ripe), watermelon, nectarines	Ripeness affects carbohydrate composition

How Cooking Affects Oligosaccharides

The way food is prepared can impact its oligosaccharide content. For instance, soaking and pressure-cooking legumes, such as beans and lentils, can help reduce the oligosaccharide content, which may make them easier to digest for those with sensitivities. The water used for soaking should be discarded. However, some cooking methods, like boiling, may not remove a significant amount of the compounds. For many, slowly reintroducing these foods can help the gut microbiome adapt.

The Health Benefits and Considerations

For most people, a diet rich in oligosaccharides is highly beneficial. These prebiotics support a healthy gut microbiome, which is linked to improved immunity, better nutrient absorption, and reduced inflammation. The SCFAs produced during fermentation are also important for gut barrier integrity and overall metabolic health.

However, for individuals with conditions like Irritable Bowel Syndrome (IBS), consuming foods high in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs) can trigger symptoms like bloating, gas, and abdominal pain. In these cases, a low-FODMAP diet, guided by a healthcare professional, may be necessary to identify trigger foods.

Conclusion

From everyday ingredients like onions and garlic to staples like lentils and wheat, oligosaccharides are widespread in a healthy, balanced diet. They play a crucial role as prebiotics, nourishing the beneficial bacteria in your gut. While most people can enjoy these foods and reap the digestive benefits, those with sensitive digestive systems should be mindful of their intake and consult with a healthcare professional to determine their tolerance. Incorporating a variety of oligosaccharide-rich foods is an effective strategy for supporting a diverse and thriving gut microbiome.

Visit the FODMAP Everyday website for more information on the types of FODMAPs and managing them in your diet.

Frequently Asked Questions

Oligosaccharides are a specific type of fiber, often referred to as prebiotic fiber. While all oligosaccharides are fiber, not all fiber is prebiotic. Other types of fiber, like cellulose, add bulk but do not specifically feed beneficial gut bacteria.

Yes, oligosaccharides can cause gas. Because they are not digested in the small intestine, they are fermented by bacteria in the large intestine. This process produces gas, which can lead to bloating and flatulence, especially for individuals who are not accustomed to a high-fiber diet.

Yes, inulin is a type of oligosaccharide, specifically a fructan. It is a polymer of fructose units and is commonly found in foods like chicory root, garlic, and onions.

People with Irritable Bowel Syndrome (IBS) often find that foods high in oligosaccharides and other FODMAPs trigger their symptoms. They may benefit from a low-FODMAP diet, which involves a period of elimination followed by controlled reintroduction to determine tolerance levels.

Most beans and legumes, including lentils, chickpeas, and kidney beans, contain significant amounts of oligosaccharides, primarily galacto-oligosaccharides (GOS) and raffinose. Cooking methods like soaking and pressure-cooking can help reduce the content.

Human milk oligosaccharides (HMOs) are a unique type of oligosaccharide that serve as prebiotics for the infant's developing gut microbiome. They help establish a healthy bacterial balance and contribute to the infant's immune system.

Yes, food manufacturers sometimes add oligosaccharides, often in the form of inulin, to processed foods. This is done to increase fiber content, modify texture, or serve as a low-calorie sweetener. Look for terms like 'inulin' or 'chicory root fiber' on the ingredient list.