Guide
Does plant protein cause diarrhea, bloating or constipation?
Legumes as a food group carry gas-causing oligosaccharides, but isolating the protein out of a bean removes most of the carbohydrate that carries them; the closest comparable trial found low, similar digestive symptoms between a plant protein and whey, and no research was found on acid reflux or breakouts from a protein powder specifically.
It can, for the same reason beans sometimes do — legumes carry gas-causing carbohydrates — but isolating the protein out of a bean removes most of that carbohydrate in the process. No trial has tested digestive tolerance for our specific fava bean and yeast blend, so the closest evidence comes from a different plant protein and from what's actually on our label.
The mechanism: gas-causing carbohydrates in legumes
Legumes contain raffinose-family oligosaccharides (RFOs), a type of carbohydrate the small intestine can't fully break down. Gut bacteria in the large intestine ferment them instead, producing gas — the biological basis for "beans and gas." A 2026 food-science study measuring RFO levels across dry bean varieties found the amount varies up to 1.7-fold by variety and growing conditions, and that canning reduces RFO content by 30–69% through leaching into the canning liquid. That study tested dry bean (Phaseolus) varieties, not fava beans specifically, and measured whole and canned beans, not an isolated protein powder — but it establishes that RFO content is processing-dependent, not fixed.
Isolating protein from a bean goes further than canning: it's specifically designed to concentrate the protein and strip out the surrounding carbohydrate, fat and fiber. That typically removes much of what would carry RFOs along with it. Nobody has measured RFO content directly in a fava bean protein isolate to confirm how much survives that process, so we can't give you a number — only the general processing logic.
The closest trial we found
A randomized crossover trial in 9 postmenopausal women compared an acute 29.5 g dose of almond protein, a 29.5 g dose of whey protein, a placebo and water, tracking gastrointestinal symptoms over 180 minutes. Symptom burden was low across all four drinks, with no severe symptoms reported and no meaningful difference between the almond (plant) protein and whey. Almond isn't a legume and isn't our fava bean and yeast blend, the trial was small, and it measured a single acute dose rather than repeated daily use — but it's the closest head-to-head digestive-tolerance data available for a plant protein against whey.
What's on our label that could play a role
Per two-scoop serving: 1 g of dietary fiber and 1 g of total sugar, sweetened with stevia leaf extract. Sugar alcohols (erythritol, xylitol, sorbitol) are a well-established cause of bloating, gas and loose stools in other protein powders because they're poorly absorbed in the small intestine — our label doesn't use one. MCT Oil Powder is also in the blend without a stated gram amount; MCT oil in larger doses is a known cause of digestive upset in its own right, but we can't speak to a dose-related effect here because the label doesn't state how much is in a serving.
Acid reflux and breakouts: no research found either way
We found no clinical trial testing plant protein powder, or a fava bean and yeast blend specifically, for acid reflux or for skin breakouts. That's an absence of evidence, not evidence of safety or of a problem — we're not making a claim in either direction on these two.
Questions people ask
Can plant protein cause gas?
It's plausible for the same reason legumes generally can — gas-causing oligosaccharides — though isolating the protein typically removes most of that carbohydrate. No dedicated trial has tested gas specifically for a fava bean and yeast blend; the closest comparable trial (almond protein vs. whey) found low symptom burden for both.
Can plant protein cause acid reflux?
No research was found testing this specifically. We're not going to guess at an answer we don't have evidence for.
Can plant protein cause breakouts?
No research was found linking a fava bean and yeast protein blend to skin breakouts. As with reflux, that's a gap in the evidence, not a finding either way.
Does plant protein make you poop more?
Possibly, if the fiber or carbohydrate content of a given product affects your digestion — ours carries 1 g of fiber per serving, on the low end. No trial measured stool frequency for our blend specifically.
Is plant protein easier on the stomach than whey?
The one head-to-head trial we found (almond protein vs. whey) showed no meaningful difference in digestive symptoms between the two. That's a different plant source than ours, so it's suggestive rather than conclusive for a fava bean and yeast blend.
Related reading: plant protein side effects, how much plant protein is too much, and plant protein: what the research does and doesn't show.
Sources
- Multi-environment evaluation of raffinose-family oligosaccharide content in diverse dry bean varieties and their reduction upon canning A 2026 food-science study found the gas-causing carbohydrates in dry beans vary widely by variety and growing conditions, and that canning removes 30-69% of them — evidence about whole beans generally, not about fava bean protein isolate specifically.
- Almond protein and whey protein beverages elicit comparable appetite regulation, gastrointestinal symptoms and hydration responses in postmenopausal women: a randomised crossover trial In a small trial of 9 postmenopausal women, a plant protein drink (almond, not fava bean or yeast) caused about as few digestive symptoms as whey protein — both were low across the board.
*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.
