Does alfalfa cause diarrhea, bloating or constipation?

The one controlled human trial on alfalfa recorded a single case of abdominal bloating out of 60 participants — the only systematic digestive-tolerability data that exists for this ingredient. Constipation isn't documented at all. Raw alfalfa sprouts carry a separate diarrhea risk, but it comes from bacterial contamination, not digestive intolerance.

What the one controlled trial reported

A 2024 randomized trial gave 60 men 6 g/day of alfalfa seed powder, alongside vitamin E, for 12 weeks. One participant withdrew due to abdominal bloating; one withdrew due to a respiratory allergic reaction. No other digestive complaints were reported in either the alfalfa or the comparison group. That's a single case in a small trial, not a rate you can generalize from, but it's the only controlled human tolerability data alfalfa has. Separately, NIH's LactMed monograph on alfalfa describes it as generally well tolerated as a food, with no broader pattern of digestive complaints documented. See alfalfa side effects for the full tolerability picture, including the rarer, more serious reactions.

Constipation isn't a documented alfalfa effect

We didn't find research or case reports linking alfalfa to constipation specifically. If you're constipated on a combination product that includes alfalfa alongside other ingredients, another component of the formula is a more likely explanation than the alfalfa itself.

Raw sprouts: a different cause of diarrhea entirely

This section is about fresh sprouts, not dried-leaf capsules or tea. A 2021 review of sprout-related outbreaks found that sprout consumption has been linked to more than 60 documented foodborne illness outbreaks worldwide since 1988, and that alfalfa sprouts were the sprout most often implicated, with Salmonella and Shiga toxin-producing E. coli the most common pathogens — both of which cause diarrhea as an infection symptom, not a digestive-tolerance reaction to the plant itself. A separate international review of sprout-associated infections notes that rinsing sprouts at home doesn't reliably remove contamination once it's present, and recommends that children, older adults, pregnant people and anyone with a weakened immune system avoid raw sprouts entirely or cook them thoroughly first. If diarrhea follows eating raw alfalfa sprouts specifically, food-safety infection is a more likely explanation than a dried-leaf reaction would be — ask a doctor about it, especially with fever or blood in the stool.

Questions people ask

Does alfalfa cause diarrhea?

Not in the one controlled trial that exists — the single digestive complaint reported was bloating, not diarrhea. Raw sprouts can cause diarrhea through bacterial contamination, which is a separate issue from the plant itself.

Does alfalfa cause bloating?

One participant in a 60-person trial withdrew for abdominal bloating at 6 g/day of seed powder over 12 weeks. That's the only controlled data point; it's not established how common the effect is.

Can alfalfa cause constipation?

We didn't find research documenting this as an alfalfa effect. If it's happening on a combination product, check what else is in it.

Are alfalfa sprouts safe to eat?

Alfalfa sprouts have been the sprout most commonly linked to Salmonella and E. coli outbreaks. That risk is about the raw, fresh food and how it's grown, not about digestive intolerance to alfalfa itself.

Related reading: alfalfa side effects, who should not take alfalfa, and alfalfa dosage.