Side Effects of Muscle Milk

Muscle Milk is a drink produced by GNC. It is rich in protein and comes in a variety of flavors like vanilla, chocolate, cookies and cream and strawberry. Although Muscle Milk is fortified with numerous minerals and vitamins, there are several side effects that you should look out for.

A bodybuilder is drinking a protein shake. (Image: Ibrakovic/iStock/Getty Images)

Weight Gain

According to GNC, one serving of Muscle Milk contains around 330 calories. Since the shakes are small in size, many people find them convenient to use as an after workout drink or snack. Being high in calories, this can cause you to take in more calories than you normally would, which can cause a gain in weight.

Vitamin Toxicity

GNC states that each Muscle Milk shake contains 88 IU of Vitamin D and 1,100 IU of Vitamin A. Although both vitamins are healthy at normal levels, they are fat soluble and any excess intake is not readily excreted from the body. The upper level of these vitamins that your body can ingest before toxicity occurs will vary depending on your metabolism, sex, weight and height. It is possible that drinking too many servings of Muscle Milk in one day can cause you to exceed your upper level of vitamin intake. This can cause side effects including headaches, vomiting and nausea.

Intesitnal Gas

Crystalline fructose is the first ingredient in Muscle Milk and makes up the majority of the drink. According to Dr. Gabe Mirkin, who is the author of "The Healthy Heart Miracle" and board-certified in four specialties, crystalline fructose may cause intestinal gas and bloating in many people.


Aside from intestinal gas, crystalline fructose also causes diarrhea in some people. This symptom is especially common in those who already suffer from irritable bowel syndrome.

Stomach Cramping

According to Dr. Mirkin, products that include large amounts of sugar fructose can cause stomach cramping. Since sugar fructose is one of the main ingredients in Muscle Milk, it has been known to cause stomach pains.

Increased Energy

Drinking Muscle Milk on a regular basis can raise energy levels in the body. By allowing the body to retain more energy, proteins and amino acids are made available for both muscle growth and function instead. The protein found in Muscle Milk can aid with muscular contraction, making the motion flexibility in the body significantly higher.

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