3 Potential Causes of Whey Protein Constipation or Diarrhea

3 Reasons Whey Protein Powder Can Cause Digestive Issues

With so many protein supplements available on the market, it might feel easiest to choose a product like whey that is clearly popular and well-regarded.

However, if you’re finding that whey protein causes consistent digestive issues, it can be helpful to learn a bit more about the product and explore all your options before settling.

Gaining confidence in a supplement can be tricky because the U.S. Food & Drug Administration (FDA) does not approve supplements before they’re advertised to the public. But there still is plenty of information available on the origins, production process, and nutritional value of whey.

Next up video playing in 10 seconds

7 Protein Mistakes

What Is Whey?

Whey is a byproduct of the cheese-making process, according to Cleveland Clinic.

This byproduct, often used as a protein supplement, is the liquid that's left over when milk curdles into curds (which are the main ingredient of cheese). When you pasteurize and dry this liquid, it becomes the powder that you add to your protein shakes.

There are a few types of whey powder, according to Cleveland Clinic, including:

Concentrate: This type is often found in protein bars and drinks, and can contain a wide range of protein, lactose, and fat.

Isolate: This kind is high in protein and low in fat and lactose.

Hydrolysate: This type is typically the easiest to digest because the protein is already partially broken down.

While some powders are gentler on your digestive tract than others, taking whey protein can indeed lead to digestive issues like constipation, diarrhea, or nausea for some people, according to Cleveland Clinic.

Here are the common reasons whey protein can cause constipation and other digestive problems (and how to deal with it).

1. It Contains Lactose

If you regularly experience constipation from whey protein, a milk sugar called lactose could be to blame. That's because whey is made up of milk proteins and thus contains lactose, according to Cleveland Clinic.

And whey protein constipation isn't the only symptom to look out for; if you're lactose intolerant, the lactose in your powder can trigger digestive issues like:

Diarrhea

Nausea

Bloating

Cramping

If you're lactose intolerant, you might want to opt for a whey protein isolate, which has the least amount of lactose per serving. You can also take over-the-counter lactase supplements to help your body break down lactose, according to Mayo Clinic.

Do not take any whey protein products if you have a milk allergy, Cleveland Clinic notes.

2. It Can Contain Added Sugars

Another potential reason whey powder causes diarrhea and other gastrointestinal issues is because these products can contain added sugars or artificial sweeteners, according to Cleveland Clinic.

For some people, ingesting all that sugar or artificial sweetener at once can trigger diarrhea, according to Harvard Health Publishing. And according to Mayo Clinic, sweeteners like sugar alcohols, stevia, and luo han guo can lead to gas, bloating, and diarrhea.

If whey protein and gas seem to go hand-in-hand for you, check the label before you buy the product to make sure that whey is the only ingredient listed, according to Cleveland Clinic.

Some protein powders can also contain additives like artificial flavoring or fillers, according to Cleveland Clinic, which could further contribute to your symptoms.

3. You Need More Fiber

It may not be the whey protein that is causing digestive issues. It could be that you need more fiber to prevent constipation, according to Johns Hopkins Medicine.

What's more, eating all that protein can fill you up and potentially deter you from eating fiber-rich foods like fruits and vegetables, according to Harvard Health Publishing. This can further contribute to constipation from whey protein.

There's no magic high-fiber protein powder for constipation, so make sure you're eating plenty of fibrous foods to prevent digestive issues from a high-protein diet.

Per the 2020-2025 Dietary Guidelines for Americans, adults should aim to eat between 22 and 34 grams (g) of fiber per day (14 g for every 1,000 calories eaten).

Harvard Health Publishing: "The Hidden Dangers of Protein Powders"

Cleveland Clinic: "Is Whey Protein Good for You?"

Mayo Clinic: "Lactose Intolerance"

Harvard Health Publishing: "Is something in your diet causing diarrhea?"

Mayo Clinic: "Artificial sweeteners"

U.S. Food and Drug Administration: “FDA 101: Dietary Supplements”

Mayo Clinic: "Diarrhea"

Harvard Health Publishing:"Extra protein is a decent dietary choice, but don’t overdo it"

U.S. Department of Agriculture and U.S. Department of Health and Human Services: "2020-2025 Dietary Guidelines for Americans"

Reyna Franco, RDN

Reyna Franco, RDN, is a New York City–based dietitian-nutritionist, certified specialist in sports dietetics, and certified personal trainer. She is a diplomate of the American Col...

Angela Brady

Angela Brady has written about health and wellness since 1997.