Whether you’re building muscle or looking to slim down, protein should serve as a fundamental part of your workout regimen. If you don’t feel like you’re getting enough protein out of your regular diet, protein supplements can serve as an easy fix, but with all of the products on GNC’s shelf, deciding which one is best for you can prove difficult. With the countless protein powders, ready-to-drink protein shakes, and protein bars on today’s market, getting your daily recommended amount of protein has become easier than balancing the right amount of red meat, poultry, eggs, and dairy in your diet. Before you settle on the best protein product, however, consider the facts.

“The largest thing to remember is that protein supplements are meant to be just that, a supplement,” Director of Iron Works Elite Fitness, Matt Fellows, told Medical Daily. “The best sources of protein are whole foods such as free-range eggs and grass-fed meats. For vegetarians, most plant proteins are incomplete and require combinations of vegetables to complete the protein.”

First off, protein is necessary to keep our body’s cells, tissues, and organs functioning. Although our bodies produce some of the protein we require (20 percent of our total body weight is protein), it does not produce some of the amino acids that make up protein. There are all together 20 different amino acids that serve as the building blocks of protein, most of which are provided for in our diet. Essential amino acids are found in various animal protein sources including fish, chicken, red meat, milk, eggs, and cheese. Not a fan of fish, chicken, red meat, milk, eggs, and cheese? Here’s where protein supplements come into play. Protein in supplement form (non-animal protein) falls under three categories: whey, soy, and casein.

Whey

The most popular form of protein, whey protein, comes from the liquid part of milk. Since our bodies can break down whey protein and absorb its nutrients at a fast pace, it is often referred to as the “fast-acting” protein. Whey protein itself can also be broken down into several subcategories including concentrates and isolates. Whey concentrate is usually made up of between 70 and 80 percent protein with relatively low amounts of lactose and fat. Containing upward of 95 percent protein with virtually no lactose or fat, whey isolate may seem like the better option. However, there are many useful compounds found in whey concentrate that are not found isolate. They include phospholipids, conjugated linoleic acid, immunoglobulins, and lactoferrin. If you’re looking for the most amount of protein to absorb in the quickest amount of time, whey isolate is your best bet.

“Many manufacturers will include ‘proprietary blends’ with no further detail,” Fellows said. “Others will include their ‘ultimate protein complex’ and include a very unspecific list of proteins. The protein type for which to look is whey isolate. Whey concentrate is less easily processed by the body.”

Soy

If you’re dieting and working out on a budget, soy protein is a good way to get a lot of those essential amino acids without the added fat, cholesterol, and lactose. Soy protein can also serve as a meat substitute for any vegetarian looking to build muscle. With components such as saponins, phytosterols, and isoflavones, it has also been known to boost immune function and lower your body’s cholesterol levels. Unfortunately, soy protein lacks many of the branched chain amino acids offered by most whey protein products. Branched chain amino acids are not only good for building muscle mass, but also for retaining mass by reducing the rate at which protein breaks down in our body.

“Soy protein is less effective than whey, but also less expensive,” Fellows explained. “Whey protein is often heat processed, damaging the protein and hindering the effectiveness, though also saving cost. The most effective and useful protein is a cold processed whey protein. The best shakes and powders will also include micellar casein, a slow digesting protein that allows the body to continue to recover and have a steady supply of proteins.”

Casein

Also known as the “slow-acting” protein, casein protein is derived from the curds of milk as opposed to the liquid. Since it does come from the lumpy curd part of cow milk, it obviously takes longer for our body to breakdown casein protein. This type of protein also contains a different sequence of amino acids compared to whey protein. One of these amino acids is glutamine. In terms of reducing soreness, repairing muscles, and recovering from an intense workout, glutamine is the most important amino acid your body requires. This makes casein protein a favorite among athletes going for endurance. A benefit of casein taking longer to digest is that it can provide the body with energy while you sleep. For that reason, many workout enthusiasts choose to save their casein protein shake for a bedtime snack.

“Protein shakes and bars can be both an effective way to lose AND gain weight,” Chief Clinical Dietician at Workmen's Circle Multicare Center, Felice Kosakavich, told Medical Daily. “The trick is to read the labels carefully and choose low calorie low sugar options. Protein is important to maintain muscle and other vital body organs. Most people get enough protein eating a balanced diet but many people find higher protein, low carb snacks fill them up and keep them satisfied longer than sugar and carbohydrates alone.  Proteins take longer for the body to digest helping the body maintain a steady glucose level, but our body’s breakdown carbohydrates quickly into sugar, causing spikes in our blood glucose making us continue snacking because we do not feel full.”

Remember, 10 to 35 percent of your daily calorie intake should come from protein. For men over the age of 19, the Recommended Dietary Allowances (RDA) of protein is 56 grams per day. The RDA for women over the age of 19 is 46 grams of protein each day. When it comes to protein powders, ready-to-drink shakes, and bars, it doesn’t matter as long as you’re combining the right amount of protein with the right amount of calories, sugars, fat, and carbs. Post-workout protein shakes (whey and soy) should be taken in the 30-minute recovery window immediately following your exercise. Taking your protein in combination with healthy carbohydrates like oats will maximize muscle-protein synthesis.