The Power of Pro Series: 50 g high-quality protein per serving to help rebuild muscles after exercise. 3 g sugar per serving. Excellent source of 20 vitamins and minerals. Vitamin D and calcium for strong bones. Energizing. Muscle maintenance. Helps rebuild muscle. On-the-go use. In-between meals. Post-workout recovery. The Science Behind Protein: Muscle Milk Pro-Series contains a combination of high-quality slow releasing and fast releasing proteins to help increase amio acids levels. Essential amino acids, including leucine, play a role in muscle growth. Protein also helps support muscle rebuilding and maintenance of muscle mass.