Does Taking Whey Protein Cause Stomach Problems or Diarrhea?

A blended drink that contains whey protein can serve as a meal replacement or provide valuable pre- or post-workout nutrition. For some people, however, this drink might lead to a sudden bathroom visit. Although whey protein affects everyone differently, a side effect of this product is a heightened risk of diarrhea or stomach discomfort.

Close-up of large whey pile.
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Side Effects Include Bloating and Diarrhea

Just as some people have adverse reactions to foods that don't affect the bulk of the population, some people report side effects of drinking whey protein. These side effects can include stomach bloating, excess gas, cramps and diarrhea. It's possible you might have an allergy or sensitivity to whey protein, but it's also possible you've consumed too much. Try lowering your next dose and noting the side effects. A typical dose of whey protein is 20 to 30 grams per day. If you're lactose-intolerant, look for a brand of whey protein labeled lactose-free. Whey protein isolate, for example, doesn't contain lactose.

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