Made from amino acids, protein is considered the essential building block of life.
Every cell in the body uses protein to function effectively, so it’s no wonder protein shakes and supplements are popular.
But there’s a lot more to protein than meets the eye; it’s worth taking a closer look at protein’s many benefits.
Protein is most often used to build muscle, especially after high intensity workouts and weight training.
Whey and casein protein specifically contains high levels of branched-chain amino acids which stimulate muscle protein synthesis. An hour after exercise, study subjects who took 20 g whey or casein protein experienced increased muscle protein net balance, resulting in muscle growth. 
Following 11 weeks of training and multiple forms of supplementation, participants taking whey protein saw a significant increase in muscle fiber size and strength. 
Muscle Recovery and Repair
During exercise, muscle glycogen stores, which act as fuel, are exhausted. Protein replenishes muscle glycogen at an accelerated rate, rapidly allowing muscles to recover.
A 28 g protein supplement was given to study participants after intense cycling. After 240 minutes, muscle glycogen stores were significantly higher in the protein group compared to others taking carbohydrates. 
Damaged or torn muscles also need protein to be repaired. Extra protein improves muscle cells’ ability to replenish and form new muscle fibers.
While more scientific research needs to be done, some experts suggest protein decreases appetite and blood fats. This may be caused by a signal protein sends to the brain that lowers levels of appetite stimulating hormones. 
In one animal study, researchers found soy protein regulated hormones and mechanisms that boosted metabolism in rats. After 3 injections of soy protein, weight loss decreased significantly. 
A Healthy Heart
According to one Harvard review, the FDA first allowed advertisers to claim soy protein “may reduce the risk of heart disease” in 1999 because preliminary research showed soy protein lowered levels of LDL, or bad cholesterol.
Research since has been inconclusive, but soy protein supplements are considered “good for the heart and blood vessels because they usually replace less healthful choices, like red meat, and because they deliver plenty of polyunsaturated fat, fiber, vitamins, and minerals, and are low in saturated fat.” 
Because all cells need protein, all cells benefit from protein supplementation.
Bones, cartilage, skin, organs, and blood are all built from protein. Every system of the body, especially the muscular and cardiovascular systems, uses protein as a source of energy and repair.
However, protein is especially essential during childhood, adolescence, and pregnancy. At 37 weeks pregnant, protein begins to form a baby’s brain. By the final trimester, when the baby’s brain is growing rapidly, protein is even more critical.  
Before using a protein supplement during pregnancy, however, make sure to consult with your medical care providers. To maximize benefits and minimize side effect risks, always take protein supplements and shakes as directed by manufactures.
 Tipton, K. D., T. A. Elliott, M. G. Cree, SE Wolf, A. P. Sanford, and R. R. Wolfe. “Ingestion of Casein and Whey Proteins Result in Muscle Anabolism after Resistance Exercise.” Medicine and Science in Sports and Exercise (2004): n. pag. Web. http://www.ncbi.nlm.nih.gov/pubmed/15570142.
 Cribb P, Williams A, Stathis C, Carey M, Hayes A. Effects of whey isolate, creatine, and resistance training on muscle hypertrophy. Medicine & Science in Sports & Exercise. 2007;39(2):298–307. Web. http://www.ncbi.nlm.nih.gov/pubmed/17277594
 Ivy, John L., et al. “Early postexercise muscle glycogen recovery is enhanced with a carbohydrate-protein supplement.” Journal of Applied Physiology 93.4 (2002): 1337-1344. Web. http://jap.physiology.org/content/93/4/1337.short
 “High Protein Diet for Weight Loss.” WebMD. Available from: http://www.webmd.com/diet/guide/high-protein-diet-weight-loss
 “How Does Soy Promote Weight Loss?” Science Daily. Available from: http://www.sciencedaily.com/releases/2007/05/070501115010.htm
 “Protein: Moving Closer to Center Stage.” Harvard School of Public Health. Available from: http://www.hsph.harvard.edu/nutritionsource/protein-full-story/
 “Protein in Diet.” MedlinePlus. Available from: http://www.nlm.nih.gov/medlineplus/ency/article/002467.htm
 “Benefits of Protein During Pregnancy.” What To Expect. Available from: http://www.whattoexpect.com/pregnancy/eating-well/week-37/protein.aspx