Protein supplements can help you reach your fitness goals by replacing depleted proteins and assisting in muscle growth and repair. No matter how beneficial they are, though, you don't want to put up with digestion problems every time you drink your shake -- that might be two or three times per day for some people. Fortunately, most digestion issues associated with protein supplements can be easily fixed with a little substitution. If your problems persist, contact your doctor for a complete workup to rule out enzyme deficiencies.
People who are lactose intolerant have a minefield of potential pitfalls to navigate when it comes to protein supplementation. The two most popular sources of supplemental protein, whey and casein, are derived from milk, and may cause negative side effects if you cannot digest lactose. Choosing a whey protein isolate may help because it contains only minute amounts of lactose, but use a lactase supplement or choose a different protein source if your symptoms are severe. Also, don't mix your protein powder with cow's milk as indicated on the label -- choose soy or almond milk, or simply mix it with water.
Supplement makers must make their protein powder taste good, but people who purchase such products won't stand for a high sugar content. The solution is sugar alcohols, which are low-calorie sugar substitutes that affect the blood sugar differently than sugar while providing sweetness and bulk to the supplement. A 2002 study in "Pure and Applied Chemistry" found that sugar alcohols can cause temporary diarrhea in some people, but the effect is unlikely at a dose of 0.3 g per kg of body weight. Read your ingredient label carefully -- if you see words ending in "-itol", your protein supplement contains sugar alcohols. Look for a sugar-only version, or a version with a lower sugar alcohol concentration.
Too Few Carbohydrates
If you are using a low-carb protein shake, it may be sitting in your stomach longer than usual, causing bloating, gas and other negative effects. Protein takes longer to digest than carbohydrates, so the more carbs in your shake, the quicker the bulk of it will leave your stomach. If you are using a casein powder, the effect is even more pronounced, because casein is a very slow-digesting protein. Look for a protein powder with a more balanced protein-to-carb ratio, or choose a faster-digesting protein, such as whey or soy.
Your digestion problems may not be caused by the powder itself at all, but rather by your preparation method. The instructions on most bottles tell you to mix the powder and milk in a blender with the addition of ice cubes to get the thickest, creamiest shake. While this method certainly makes it taste better, it incorporates plenty of air into the mix. You swallow the air when you drink the shake, and the air gets released in your stomach as the shake itself digests. This can result in bloating, cramping and gas, but it is easy enough to resolve. Simply mix your shake in a shaker bottle, and shake only until it is blended. Shop around for an "easy-mix" powder that dissolves completely and quickly to minimize the air bubbles.