Protein Powder and Digestion

January 14, 2023
| Created by Hannah Langley, MS, RDN, CD

Are you overwhelmed by the wide variety of protein powders in the sports nutrition aisle and aren’t sure which will best meet your individual needs? This article is part of a series, written by Harmons Dietitian Hannah Langley, to take an extensive look at protein powders and help you make the most informed choice when shopping for your health. 

Lactose in Milk Proteins

Lactose is a type of sugar found in milk and dairy products. People that are lactose intolerance lack enough of the enzyme lactase, which is responsible for breaking down lactose small enough for our body to absorb it. Consuming too much lactose and not having enough lactase to break it down can result in nausea, bloating, cramping, and diarrhea.  

The remaining amount of lactose after the filtration of milk proteins, like whey and casein, is so small that these protein powders are typically well-tolerated by individuals with lactose intolerance. Whey protein isolates and hydrolysates may be ideal for individuals who experience the undesirable side effects of lactose intolerance when using a whey concentrate. This is because isolates and hydrolysates go through additional processing which reduces their lactose content to even smaller than that of concentrates. Plant-based proteins do not naturally contain lactose and can also be a suitable option. 

Naturally Gluten Free vs Certified Gluten Free

Gluten is a protein found in wheat, rye, and barley products that does not need to be limited in your diet unless you Celiac or gluten intolerance. Many protein powders do not incorporate these grains in their ingredients list, resulting in a naturally gluten-free product which can be stated on the label. Those with Celiac, however, should consider choosing a protein powder that has been certified as gluten-free to avoid cross contamination with any gluten-containing ingredients during manufacturing and to ensure the product has been tested for gluten prior to being sold. A few reputable certifying bodies include The Gluten Free Certification Organization and NSF Certified Gluten Free. 

Fiber Blends

Fiber and fiber blends are becoming more and more common in protein powders. Chicory root fiber, inulin, and allulose provide a sweet taste and are currently classified as prebiotic fibers, meaning they are not fully digested in the small intestine and feed the good gut bacteria in the large intestine and colon. This can be beneficial for those looking to increase satiety and their dietary fiber intake, but there are a few things to keep in mind. First, fiber blends may decrease the rate of utilization of your protein powder, which is undesirable if you’re using the powder for post-exercise recovery. Consuming a lot of fiber too quickly, especially if you’re not used to higher amounts of fiber, can cause nausea, bloating, constipation, and diarrhea. The amount of fiber added to protein powders is typically low enough to have minimal side effects, though these fibers may not be suitable for individuals on a low FODMAP diet. 

MCT Powder

Medium chain triglycerides (MCT) are a type of rapidly digested saturated fat. Some protein powder blends on the market include added MCT powder, which may increase satiety, provide an energy source for those on a very low-carb diet, and create a richer-textured product. Two of the common claims regarding MCTs in sports nutrition are their ability to reduce lactate post-exercise and to aid in fat loss; research regarding MCTs effect on lactate has been largely inconclusive and it’s effect of fat loss is often taken out of context. The research that has shown any significant changes in fat loss occurs when MCTs are used to replace long chain triglycerides, meaning MCTs are not helpful for fat loss in and of themself. Keep in mind that MCT powder contributes to daily saturated fat intake, which is a nutrient associated with chronic disease risk as most Americans typically overconsume it.

So why are MCTs important to consider for digestion? Because they are more rapidly digested than other types of fats, they can cause a laxative effect when consumed on an empty stomach or in excess. MCT powder is typically better tolerated than MCT oil because it has a slightly lower concentration of MCTs for the same volume. 

Digestive Enzymes

Some companies include digestive enzymes in their protein powder blends to aid digestion and potentially increase the rate of utilization of the product. The inclusion of these enzymes isn’t necessary but may be beneficial in certain circumstances. First, it may help athletes and individuals that require a high calorie, high protein diet better absorb and utilize very large doses of protein. It may also be beneficial for those that experience GI discomfort when using their preferred protein powder, though the plant-based enzymes that are typically used tend to be less efficient than the enzymes naturally occurring in your GI tract. If you experience GI discomfort while using a protein powder, please discuss it with your Harmons Dietitian. 

Sugar Alcohols

Sugar alcohols are a cross between sugar and alcohol molecules, called polyols. There are currently 8 sugar alcohols generally recognized as safe by the FDA, the most commonly used being xylitol, erythritol, mannitol, isomalt, and sorbitol. They are low-calorie sweeteners and can contain between 1.5-3 calories per gram. They are partially digested in the small intestine and then fermented in the large intestine. Sugar alcohols are generally well tolerated in small amounts, up to 10-15 grams per day, but excess can have a laxative effect. Sugar alcohols may also cause additional gastrointestinal upset like bloating and flatulence, and are not suitable for those following a low-FODMAP diet.  

Key Takeaways

  • Whey isolates and hydrolysates, along with plant proteins, are best for individuals with lactose intolerance. 
  • Those with Celiac should choose a protein powder that has been certified gluten free. 
  • Added fiber is good for satiety and gut bacteria, but is undesirable for post-exercise recovery and those on a low FODMAP diet. 
  • MCTs can increase satiety, provide energy for those on a low-carb diet, and create a richer product, but can have laxative effects and contribute to saturated fat intake.
  • Added digestive enzymes are not significantly beneficial, but they may help people on a high protein diet better absorb and utilize large doses of protein.
  • Sugar alcohols may cause gastrointestinal distress when consumed in excess and are not suitable for a low FODMAP diet. 

Your Harmons Dietitian can help if you have questions, would like personalized product recommendations, or are curious about your individual protein needs. Reach out to