You’ve gone gluten-free, focused on balanced meals, maybe you’ve even cut out dairy—but you’re still bloated. Many people experience this, and it’s beyond frustrating. You feel like you’re doing everything right, and still, the discomfort lingers. One common, yet often overlooked cause? FODMAPs, specifically the fructans found in garlic and onions. These can sneak into the most careful and intentional eating patterns and trigger digestive distress. 

What are Fructans and Why Do They Cause Bloating?

Fructans are a type of carbohydrate found in foods like wheat, leeks, asparagus, artichokes, and most notably, onions and garlic. They belong to the FODMAP family: fermentable oligosaccharides, disaccharides, monosaccharides, and polyols. For people with sensitive digestive systems, such as those with IBS, these carbs are poorly absorbed in the small intestine.

When fructans reach the large intestine, they’re rapidly fermented by gut bacteria, producing gas. They also pull in water, which increases pressure in the colon. The result? Bloating, cramping, and sometimes diarrhea.

Fructans vs. Gluten: Why Cutting Gluten Might Not Be Enough

It’s a common trap: you’ve gone gluten free hoping for relief, but your bloating still hasn’t budged. The reason? You might be reacting to fructans, not gluten. 

Gluten is a protein found in wheat, barley and rye. Fructans, on the other hand, are fermentable carbohydrates that are also found in many gluten-containing and gluten-free foods. That means you can be eating gluten-free and still be getting plenty of fructans through foods like onions, garlic, leeks and many gluten-free products. 

In fact, research suggests that many people who think they’re gluten-sensitive are actually reacting to fructans instead. Understanding this distinction can be the key to unlocking real digestive relief.

How to Know If Garlic or Onions Are the Problem

Identifying a fructan sensitivity can be a powerful step toward improving your symptoms. Here are three RD-approved strategies to help you find clarity:

  • Keep a symptom journal: Track what you eat and how you feel. Bloating, cramping, or urgency after certain meals? You may notice a pattern. A Registered Dietitian (RD) can help interpret your entries and identify subtle triggers.
  • Try a short-term low-FODMAP diet: Under RD supervision, a low-FODMAP diet followed by a systemic reintroduction can help you pinpoint whether fructans, and which kinds, are causing your symptoms.
  • Watch for hidden sources in sauces, dressings, and seasoning: Garlic and onion powders are common in spice blends, condiments, marinades, and restaurant meals. If you still feel bloated after a balanced and “trigger free” meal, this might be why.

What You Can Do About It

A fructan sensitivity doesn’t mean you’re doomed to flavorless meals. Here are strategies to enjoy your food while minimizing symptoms:

  • Garlic/Onion Oil Infusions: Fructans are water-soluble but not fat-soluble. That means you can use garlic (and onion) infused oils to get the flavor without the FODMAPs. You can even make your own at home! 
  • Use Low Fructan Alternatives:  Swap onion for the green parts of scallions or chives. These provide a similar flavor without the fermentable carbs. Pre-soaking garlic or onions in water and discarding the liquid may also help reduce their fructan content.
  • Enzyme Support: Supplements like FODZYME, which contain fructan hydrolase, help break down fructans in the gut, reducing gas, water retention, and bloating. These can be used with guidance of a Registered Dietitian before or after a low-FODMAP diet.

The Bottom Line

If you’re gluten-free but still bloated, don’t panic and don’t assume it’s all in your head. Fructans are a very common and often overlooked trigger, especially for people with IBS or sensitive digestion. The good news? You don’t need to eliminate garlic and onions forever. With the right strategy, you can find a personalized threshold that works for you. 

About Culina Health

From finding the right dietitian to ongoing support, Culina Health offers holistic, inclusive, and evidence-based nutrition care that’s covered by insurance. With an easy sign-up and referral process and a secure, convenient telehealth platform, we make nutrition counseling accessible and impactful – from the comfort of your own space. Want help navigating your nutrition journey? Book a session with a Culina Health Registered Dietitian who can guide you with confidence.