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Why Do Protein Shakes Give Me Diarrhea?

Why Do Protein Shakes Give Me Diarrhea?
An avocado banana smoothie on a wooden table. Photo Credit: Lecic/iStock/Getty Images

While protein shakes give you a boost of protein, they aren't for everyone. Some people who drink these beverages experience side effects, such as gas, bloating and diarrhea, because of ingredients commonly found in the shakes. These include protein, milk-based ingredients, sugar alcohols and fiber. Try a shake made with other ingredients to help you solve this problem.

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Excessive Protein Intake

Most people get plenty of protein in their diet and don't really need the additional protein found in shakes. People who drink multiple shakes per day on top of a high-protein diet may end up getting so much protein throughout the day or in one sitting that it causes diarrhea. You can only digest between 5 and 9 grams of protein per hour. Women typically need about 46 grams of protein per day, and men about 56 grams. Protein should make up between 10 and 35 percent of your calories each day.

Lactose Intolerance or Milk Allergies

Protein shakes are often based on ingredients from milk, such as whey and casein. If you're allergic to milk or you are lactose-intolerant, these ingredients could cause diarrhea. In the case of allergies, it might also cause a more severe reaction, including itchiness, swelling, congestion, shortness of breath, vomiting, nausea, lightheadedness or fainting. Switch to a non-dairy protein shake to avoid these issues.

Types of Carbohydrates

Certain types of carbohydrates found in some protein shakes could also cause diarrhea. Drastically increasing your fiber intake with a high-fiber protein shake could cause diarrhea, gas or bloating. Some protein shakes also contain sugar alcohols, which many people have difficulty digesting.

Other Considerations

Testing conducted by "Consumer Reports" found that many protein powders and drinks are contaminated with heavy metals, including arsenic, lead, mercury and cadmium. Excessive exposure to these heavy metals could increase your risk for health problems, including organ damage. You'd be better off getting your protein from foods that typically contain little or no heavy metals, such as eggs, yogurt, milk, red meat and poultry. Choose low-fat versions of these high-protein foods for the best health results.

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