Red onions can upset your stomach because they contain fructans, a type of carbohydrate your gut doesn't break down easily. These fructans ferment in your intestines, leading to digestive distress.
How Fructans Cause Stomach Discomfort
The primary reason red onions (and other onions) cause stomach problems is their high fructan content. As stated in multiple sources like Livestrong, Julien Nutrition, and WebMD, fructans are oligosaccharides, or complex carbohydrates, that your small intestine struggles to absorb. This leads to fermentation in the large intestine, producing gas, bloating, and potentially diarrhea. This effect is amplified when consuming raw onions, as highlighted in a Reddit discussion on /r/OnionLovers.
Symptoms of Fructan Intolerance from Onions
Symptoms can vary but often include:
- Bloating
- Gas
- Abdominal pain or cramping
- Diarrhea
- Nausea
Reducing Onion-Related Stomach Issues
Several strategies can minimize digestive upset from red onions:
- Cook your onions: Cooking onions breaks down some of the fructans, making them easier to digest.
- Consume onions in moderation: Even cooked onions can cause problems if eaten in large quantities.
- Pair onions with other foods: Eating onions alongside foods high in fiber can help with digestion.
- Consider your individual tolerance: Some individuals are more sensitive to fructans than others. Pay attention to your body's response and adjust your consumption accordingly.
While an onion allergy is possible (Wyndly), the most likely cause of stomach pain after consuming red onions is fructan intolerance, as corroborated by multiple sources.
