Broth can cause diarrhea for several reasons, and the most likely culprit depends on whether you’re drinking homemade or store-bought, how long it was simmered, and what went into the pot. The most common triggers are histamine buildup from long cooking times, fructans from onions and garlic, high fat content, and food additives in commercial brands. Figuring out which one affects you usually comes down to a simple process of elimination.
Histamine Builds Up the Longer Broth Cooks
Histamine is a chemical your body produces naturally, but it also accumulates in foods that are aged, fermented, or cooked for extended periods. Bone broth simmered for 12 to 24 hours (as most recipes recommend) falls squarely into this category. The longer the cook time, the more histamine concentrates in the liquid.
Most people break down dietary histamine without any issue, using an enzyme produced in the gut lining. But some people don’t produce enough of that enzyme, a situation sometimes called histamine intolerance. When excess histamine hits the digestive tract, it constricts the GI tract, increases mucus production, and speeds up intestinal contractions. The result is diarrhea, often alongside bloating, headaches, or skin flushing. If you notice symptoms from other high-histamine foods like aged cheese, wine, sauerkraut, or canned fish, histamine is a strong suspect.
A simple test: try a broth cooked for only 30 to 60 minutes instead of overnight. If your symptoms improve, histamine accumulation is likely the issue.
Onions and Garlic Are High-FODMAP Ingredients
Nearly every broth recipe starts with onions and garlic. Both are loaded with fructans, a type of short-chain carbohydrate classified as a FODMAP. Fructans aren’t absorbed well in the small intestine. Instead, they travel to the large intestine where gut bacteria ferment them rapidly, producing gas, drawing water into the bowel, and triggering diarrhea.
An estimated 24% of people with irritable bowel syndrome are sensitive to fructans specifically. But you don’t need an IBS diagnosis to react. Fructans dissolve easily into water, so simmering onions and garlic in broth for hours effectively extracts them into the liquid you’re drinking. You might tolerate a small amount of cooked onion in a stir-fry but find that a full bowl of onion-infused broth overwhelms your gut.
If you want to test this, make broth without any onion, garlic, shallots, or leeks. Use carrots, celery, ginger, and herbs instead. If the diarrhea stops, you’ve found your trigger.
Fat Content Can Overwhelm Digestion
Bone broth, especially when made from marrow bones, oxtail, or chicken thighs, can contain a surprisingly high amount of fat. Fat slows stomach emptying but speeds up contractions in the colon, a reflex that pushes contents through faster than your body can absorb water from them. Drinking a large mug of fatty broth on an empty stomach amplifies this effect.
If you see a visible layer of oil on your broth, that’s a clue. Skimming the fat or refrigerating the broth overnight (so the fat solidifies on top and can be removed) often solves the problem entirely. This is one of the easiest fixes to try first.
Glutamate in Long-Simmered Broth
Extended simmering breaks down proteins in bones and connective tissue into free glutamate, the same compound responsible for the savory “umami” flavor. Bone broth can be quite high in glutamate, and for some people this triggers increased bowel movements, stomach upset, bloating, or nausea.
Glutamate sensitivity is poorly understood and not universally accepted as a clinical diagnosis, but the pattern is real for people who experience it. If you react to other glutamate-rich foods like soy sauce, parmesan cheese, tomato paste, or mushrooms, the glutamate concentration in broth could be contributing to your symptoms.
Additives in Store-Bought Broth
If your diarrhea happens specifically with commercial broth or stock, the ingredient list deserves a close look. Many store-bought broths contain thickeners, stabilizers, and emulsifiers that can irritate the gut. Carrageenan, extracted from red seaweed, is one of the most studied offenders. It activates inflammatory pathways in the intestine, alters gut bacteria composition, and thins the protective mucus barrier lining the gut wall.
Other common additives linked to digestive inflammation include xanthan gum, maltodextrin, and polysorbate-80. These ingredients appear frequently in shelf-stable and boxed broths. Switching to a brand with a shorter, simpler ingredient list, or making broth at home, can help you determine whether additives are the problem.
How to Narrow Down Your Trigger
Because multiple factors can overlap in a single bowl of broth, isolating the cause takes a bit of experimentation. A practical approach is to change one variable at a time:
- Reduce cook time. Simmer for one hour instead of eight or more. This lowers both histamine and glutamate levels significantly.
- Remove onions and garlic. Make a batch with only low-FODMAP vegetables and see if symptoms change.
- Skim the fat. Refrigerate broth and remove the solidified fat layer before reheating.
- Try a plain, additive-free brand. If you normally buy boxed broth, compare your reaction to a homemade version with minimal ingredients.
- Start with smaller amounts. Even if you’re sensitive to one of these compounds, a few sips may be tolerable where a full mug is not. Dose matters.
If none of these changes help, the issue may be something more individual, like a sensitivity to collagen peptides or a coincidental association with something else you eat alongside broth (crackers, noodles, or other soup ingredients). Keeping a food diary for a week or two, noting what you ate and when symptoms appeared, can reveal patterns that aren’t obvious in the moment.