What Are Oligosaccharides?
Oligosaccharides are carbohydrates composed of a small chain of simple sugars, typically ranging from three to ten units. Unlike other carbs, the human small intestine cannot fully digest them because the necessary enzymes are lacking. This poor absorption means they travel to the large intestine, where gut bacteria ferment them. This fermentation process is what provides their prebiotic benefits but can also lead to symptoms like gas, bloating, and abdominal discomfort in sensitive people.
The two main types of oligosaccharides found in food are fructans and galacto-oligosaccharides (GOS). Many oligosaccharide-rich foods are also part of the Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols (FODMAP) diet, often recommended for managing symptoms related to IBS.
Top Foods High in Fructans
Fructans are a type of oligosaccharide made from chains of fructose. They are abundant in many plant-based foods, including vegetables, fruits, and grains.
Vegetables with High Fructan Content
- Onions and Garlic: These are some of the most concentrated sources of fructans. All varieties, including white, red, and shallots, are high, as is garlic. A common low-FODMAP alternative is using garlic-infused oil to get flavor without the fermentable carbs.
- Leeks and Scallions: The white bulb and green parts of leeks are high in fructans, while the green tops of scallions are lower in FODMAPs.
- Asparagus: Contains fructans that can cause bloating in some individuals.
- Artichokes: Both globe and Jerusalem artichokes are significant sources.
- Chicory Root: This is a major source of inulin, a type of fructan, and is often added to processed foods as a fiber supplement or sweetener.
Grains High in Fructans
- Wheat and Rye: Products like bread, pasta, and cereals made from wheat and rye are primary dietary sources of fructans. People with non-celiac gluten sensitivity may actually be reacting to the fructans, not the gluten.
- Barley: This grain also contains significant amounts of fructans.
Foods High in Galacto-Oligosaccharides (GOS)
GOS are oligosaccharides primarily found in legumes and some nuts. They are made from chains of galactose molecules.
Legumes Rich in GOS
Legumes are a cornerstone of many diets but are known for their high GOS content, which can lead to gas and bloating.
- Beans: All varieties, including kidney, black, pinto, navy, and baked beans, contain high amounts of GOS. Soaking and thoroughly rinsing canned beans can help reduce their oligosaccharide content.
- Lentils and Chickpeas: Both fresh and canned lentils and chickpeas are sources of GOS.
- Soybeans: Soy-based products like soy milk made from whole soybeans, soft tofu, and textured soy protein are high in GOS.
Nuts and Seeds with GOS
- Cashews and Pistachios: These nuts contain a high concentration of GOS. Other nuts like macadamias, pecans, and walnuts are typically lower.
Natural vs. Added Oligosaccharides
Beyond their natural presence, manufacturers often add oligosaccharides, particularly inulin and fructooligosaccharides (FOS), to processed foods to increase fiber content and improve texture. These can be found in:
- Breakfast Cereals
- Bakery Foods (breads, cakes)
- Dairy Products (yogurt, ice cream)
- Protein Bars and Meal Replacements
- Salad Dressings and Spreads
How to Reduce Oligosaccharide Content in Foods
If sensitivity to oligosaccharides exists, some cooking methods can help reduce their concentration, making certain foods more tolerable.
- Boiling and Rinsing: A significant portion of the water-soluble oligosaccharides can be leached out of legumes by boiling them and then draining and rinsing the liquid. Canned legumes that have been rinsed thoroughly are often better tolerated than cooking from scratch.
- Soaking: Soaking dried legumes before cooking can also help reduce oligosaccharide levels.
- Use Low-FODMAP Alternatives: Substitute high-oligosaccharide foods with lower-FODMAP options. For instance, use the green tops of scallions or garlic-infused oil instead of whole onions and garlic. Opt for rice, quinoa, or sourdough spelt bread over wheat-based products.
High Oligosaccharide Foods Comparison Table
| Food Category | Primary Oligosaccharide Type | High Oligosaccharide Examples | Low Oligosaccharide Alternatives |
|---|---|---|---|
| Vegetables | Fructans | Onion, garlic, artichoke, asparagus, leeks | Carrots, cucumber, spinach, bell peppers |
| Legumes | GOS & Fructans | Beans (kidney, black), chickpeas, lentils | Rinsed canned lentils, firm tofu |
| Grains | Fructans | Wheat, rye, barley | Rice, quinoa, oats, sourdough spelt bread |
| Nuts | GOS & Fructans | Cashews, pistachios | Walnuts, pecans, macadamia nuts |
Benefits and Drawbacks of Oligosaccharides
Oligosaccharides offer important health benefits by acting as prebiotics, nourishing beneficial gut bacteria. This can enhance gut microbiome diversity, improve digestive health, and potentially boost immune function.
However, their fermentation in the colon can cause symptoms like bloating, gas, cramping, and diarrhea in those with sensitive digestive systems, particularly individuals with IBS. It is recommended to increase intake of oligosaccharide-rich foods gradually to allow the gut to adapt and minimize side effects. For managing symptoms, a low-FODMAP diet may be recommended by a dietitian.
Conclusion
Foods highest in oligosaccharides include a wide range of everyday items such as onions, garlic, wheat, legumes, and certain nuts. While these foods offer significant prebiotic benefits and are generally healthy for most people, they can trigger digestive issues in sensitive individuals due to fermentation in the gut. By understanding which foods are the most concentrated sources of oligosaccharides and using preparation techniques like boiling and rinsing, those with sensitivities can better manage their symptoms. For a more structured approach, consulting with a dietitian about a low-FODMAP diet can provide personalized guidance to balance gut health and digestive comfort. For further research on managing oligosaccharide intolerance, the Monash University Low FODMAP Diet is a highly respected resource and can be found at https://www.monashfodmap.com.
Keypoints
- Primary Sources: Onions, garlic, wheat, legumes, cashews, and pistachios are among the highest sources of oligosaccharides.
- Fructans vs. GOS: The main types of oligosaccharides are fructans (found in wheat, onion, garlic) and GOS (found in legumes and certain nuts).
- Prebiotic Function: Oligosaccharides act as prebiotics, feeding beneficial gut bacteria and supporting a healthy microbiome.
- Digestive Symptoms: Poor absorption in the small intestine leads to fermentation in the colon, causing gas, bloating, and discomfort in sensitive individuals.
- Reducing Content: Boiling, soaking, and rinsing legumes can significantly reduce their oligosaccharide content.
- Low-FODMAP Alternatives: Using garlic-infused oil instead of whole garlic or opting for rice and quinoa over wheat products can help manage symptoms.
- Consultation is Key: For managing significant symptoms, consulting a healthcare professional or dietitian is advisable to explore a low-FODMAP diet.
