What foods contain galacto-oligosaccharides?

December 12, 2025 •

4 min read

An estimated 65% of the global population has some form of lactose intolerance, yet many of these same people benefit from consuming galacto-oligosaccharides (GOS). GOS are a type of prebiotic fiber found in a variety of foods that can promote the growth of beneficial gut bacteria.

Quick Summary

Galacto-oligosaccharides (GOS) are prebiotic carbohydrates found in legumes, dairy products, nuts, and certain plant-based alternatives. These non-digestible fibers nourish beneficial gut bacteria, supporting a healthy microbiome and improving digestion.

Key Points

Legumes are a top source: Foods like lentils, chickpeas, and beans are rich in naturally occurring galacto-oligosaccharides.
Dairy contains GOS: Milk and fermented products like yogurt and kefir are natural sources of GOS.
Nuts provide GOS: Cashews and pistachios are known for their significant galacto-oligosaccharide content.
GOS are prebiotic fibers: These carbohydrates pass undigested into the colon, where they nourish beneficial gut bacteria.
Commercial products are fortified: Many infant formulas and other functional foods are supplemented with GOS to boost prebiotic effects.
Fermentation produces GOS: The process of fermenting dairy can lead to increased GOS content in products like yogurt and kefir.
GOS can cause side effects: In sensitive individuals, particularly those with IBS, high doses of GOS may lead to gas and bloating.

Introduction to Galacto-Oligosaccharides (GOS)

Galacto-oligosaccharides, or GOS, are a type of prebiotic. This means they are non-digestible fibers that pass through the upper gastrointestinal tract to be fermented by beneficial bacteria in the large intestine. These short-chain carbohydrates are often found in infant formulas to mimic the prebiotic effects of human breast milk. Incorporating foods that contain galacto-oligosaccharides into your diet can help promote a healthy, balanced gut microbiome. While often associated with dairy products, GOS are also prevalent in a variety of plant-based sources, making them accessible to most dietary preferences.

Legumes: A Powerhouse of GOS

Legumes, including beans, peas, and lentils, are one of the most well-known natural sources of galacto-oligosaccharides. These versatile foods are a staple in many cuisines and provide a significant prebiotic boost. The GOS found in legumes act as nourishment for gut bacteria, which can be particularly beneficial for those on vegetarian or vegan diets. However, for some individuals, particularly those with Irritable Bowel Syndrome (IBS), the high GOS content can cause digestive discomfort. Cooking methods and preparation can sometimes impact the GOS content, but they remain a primary source.

Common GOS-rich legumes include:

Lentils
Chickpeas (including hummus)
Kidney beans
Black beans
Pinto beans
Soybeans (and some soy products like soy milk)
Split peas

Dairy and Dairy Alternatives with GOS

Certain dairy products naturally contain or are fortified with galacto-oligosaccharides, particularly those that undergo fermentation. The manufacturing process for commercial GOS often utilizes lactose as a substrate.

Sources in this category include:

Cow's milk: Contains some natural GOS, though levels are typically lower than in breast milk.
Yogurt and Kefir: Fermentation processes can increase GOS content, and they are sometimes added deliberately to boost prebiotic effects.
Cheese and Butter: These also contain GOS, though generally in smaller quantities.
Infant Formula: GOS is frequently added to infant formulas to replicate the composition of human breast milk and promote a healthy infant gut microbiome.
Fortified Products: Some dairy alternatives, such as certain nut-based yogurts or oat milk, can contain added GOS.

Nuts and Seeds Providing GOS

Several types of nuts are excellent sources of galacto-oligosaccharides and can be incorporated into a balanced diet easily. These healthy snacks can contribute to your daily prebiotic intake and provide a variety of other nutritional benefits.

GOS-containing nuts and seeds include:

Cashews: A well-known source of GOS.
Pistachios: Also contain notable amounts of GOS.
Almonds: A source of GOS, though typically in lower concentrations than cashews and pistachios.
Pine nuts: Contain GOS and can be used in various recipes.

Vegetables and Grains

While not as high in concentration as legumes, several common vegetables and some grains also contain galacto-oligosaccharides. Including these foods can help diversify your intake of prebiotics.

Vegetable and grain sources of GOS include:

Beets: Provide a small amount of GOS.
Green peas (thawed): A source of GOS.
Taro: This root vegetable contains GOS.
Barley and Oats: These grains provide smaller amounts of GOS along with other types of fiber.
Oat milk: A plant-based milk alternative that can contain GOS.

A Comparison of GOS and Other Prebiotics

Different prebiotics offer varying benefits depending on their structure and how they are fermented by gut bacteria. The following table compares GOS with Fructo-oligosaccharides (FOS) and Inulin.


Feature	Galacto-Oligosaccharides (GOS)	Fructo-oligosaccharides (FOS)	Inulin
Primary Sources	Legumes, dairy, nuts, breast milk	Onions, garlic, bananas, chicory root	Chicory root, Jerusalem artichoke, garlic
Speed of Fermentation	Rapidly fermented by gut bacteria	Rapidly fermented	Slower fermentation due to longer chain length
Targeted Bacteria	Preferentially fermented by Bifidobacterium	Preferentially metabolized by Lactobacilli and Bifidobacterium	Fermented by a broad range of gut bacteria
Known Effects	Promotes beneficial gut bacteria, may improve mineral absorption	Promotes beneficial gut bacteria, can improve calcium absorption	Promotes beneficial gut bacteria, may improve mineral absorption
Potential Side Effects	May cause gas, bloating in sensitive individuals	Can cause gas and bloating in sensitive individuals	Can cause gas and bloating, especially in high doses

Conclusion: Making Informed Dietary Choices

Understanding what foods contain galacto-oligosaccharides allows you to make informed decisions to support your gut health. By including a diverse range of foods like legumes, certain nuts, and fermented dairy products, you can increase your intake of these beneficial prebiotics. This dietary strategy can foster a healthy and thriving gut microbiome. If you have digestive sensitivities, particularly IBS, it is important to pay attention to your body's response and potentially consult with a healthcare provider or registered dietitian to find the right balance for you. The varied sources of GOS ensure that you can likely find options that fit your personal dietary needs and preferences.

For more information on the structure and synthesis of GOS, you can read more here: Galactooligosaccharides: Synthesis, metabolism, bioactivities, and applications.

Frequently Asked Questions

GOS function as prebiotics, which are non-digestible fibers. They serve as food for beneficial bacteria, such as Bifidobacterium and Lactobacillus, in your gut, helping to promote a healthy microbiome.

Yes. While GOS are often derived from lactose, they are different molecules. GOS are not broken down in the small intestine like lactose, so they typically do not cause the same digestive issues for people with lactose intolerance.

Legumes such as lentils, chickpeas, kidney beans, and soy are known to be particularly rich in galacto-oligosaccharides.

Yes, GOS are found naturally in human breast milk, where they play a crucial role in developing a healthy gut microbiome in infants.

Some plant-based milk alternatives, particularly soy milk made from whole soybeans or oat milk, can be sources of GOS.

GOS and FOS (fructo-oligosaccharides) are both prebiotics, but they have different structures and are fermented by different types of gut bacteria. GOS are often preferentially metabolized by Bifidobacterium, while FOS may be favored by Lactobacilli.

GOS can be hidden in processed foods like some protein powders (pea or soy based), certain soups, and dips that use legume flours. They are also often added to infant formulas, functional dairy products, and certain baked goods.