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A common question I hear from patients is “What’s the best kind of protein to use for my post-workout shakes?”

Before considering the different kinds of protein, let’s consider what protein is and why it’s important. When protein is digested, it breaks down into amino acids. They are classified as essential or nonessential, which is not as complicated as it sounds.

The body cannot make essential amino acids; they must be supplied by food. Protein is needed for all stages of life—growth and development, cell and tissue repair, hormone development, and for the immune system to fight off infections.

Protein is needed for muscle contraction, healing and growth. Without adequate protein intake, your muscles won’t heal as quickly after working out, making you prone to injury. The question becomes, why drink protein shakes and what kind of protein is best for you?

Protein shakes are a quick and easy way to get good nutrition during the day, as pre-workout fuel and post-workout nutrition.

Because solid food takes time to digest and absorb, shakes provide an easy and quickly digested protein source for your body after you work out. Protein powders that are readily available include: whey, egg white, soy and casein. Whey protein has a great nutritional reputation as it provides all the essential and non-essential amino acids, as well as branched-chain amino acids (which prevent muscle oxidation and breakdown). Whey comes from dairy, without the lactose and other bioactive compounds.

There are three different types of whey—whey isolate, hydrosylate and concentrate.

Simply, whey protein isolate does not have lactose in it and is roughly 90-94% pure protein. Whey protein hydrosylate is “predigested” and very expensive, while whey protein concentrate usually has trace amounts of lactose.

Egg-white protein was the popular choice before whey became available. Like whey, egg white is an excellent source of protein to maintain or build lean muscle; it, too, is quickly digested and absorbed. Egg protein contains all the essential amino acids to rebuild after your workout. Athletes use egg protein as a staple part of their diet.

Soy protein isolate comes from soy beans and is the most popular vegetable protein supplement. Others include hemp, pea and brown rice. While the protein found in soy supplies all eight essential amino acids, it takes longer to digest and has a slow absorption rate. Casein, like whey, is derived from dairy, making up roughly 80% of the dairy protein. Like soy, it is absorbed slowly in the digestive system, while whey and egg protein are digested quickly.

Protein is measured by its biological value—the amount of protein retained after absorption and used by the tissues of the body. The higher the value, the greater bioavailability. A high biological value reflects a high level of amino acids from the protein source. According to the Journal of Sports Science and Medicine, the biological value of popular protein sources are:[spacer height=”20px”]

  • Whey — 104
  • Egg — 100
  • Soy — 74
  • Casein — 77

Whey and egg protein have the highest values and have the best bioavailability for use by muscles.

However, you should be aware that all protein sources have potential side effects.

Whey protein isolate and hydrosylate are both virtually lactose-free, thus posing no problems for those who are lactose intolerant. If you have a reaction (bloating, nausea or other GI issues) consider getting IgE food-allergy testing to see why you may be reacting to whey. Egg protein can also cause an allergic response in susceptible individuals. Again, consider food-allergy testing to explain a reaction.

As a nutritionist and physician, I strongly recommend avoiding soy and casein, as both have been shown to cause health issues. Casein, a milk protein, has been shown to be detrimental to health. The digestion of casein releases bioactive compounds, one of which is bioactive peptide beta-casomorphin 7 (BMC‑7). BMC‑7 acts like morphine in the body and is linked to type 1 diabetes, ischemic heart disease, sudden infant death syndrome, allergies, and other inflammatory conditions. Unfermented soy—the type found in powders, bars, and meal replacements—is also not as healthful as we have been led to believe.

Unfermented soy most likely comes from GMO-based soybeans that have been genetically engineered to resist the pesticide Roundup®. Genetically modified foods have been linked to infertility, low-birth-weight babies, birth defects, allergies, and a lot of other health problems.

Unfermented soy (not soaked or treated with magnesium chloride) is also loaded with anti-nutrients, which have been linked to digestive disorders, allergies, malnutrition, and suppression of the immune system.

My advice is to use whey or egg as the protein source for your post-workout smoothie—providing you have no allergies. Mix the protein with fruit and a scoop or two of a greens powder for the vitamin and mineral content.

The best time to take in this protein is right after your workout—within 30 minutes—since your body starts to heal muscles right away. Refueling your body right after your workout will help you create a healthy body composition, one which is low-fat and lean.


Jay R. Hoffman and Michael J. Falvo, Protein—which is best. Journal of Sports Science and Medicine (2004) 3, 118-130

Stanisaw Kamiñski, Anna Cieoeliñska, Elbieta Kostyra.  Polymorphism of bovine beta-casein and its potential effect on human health.  Journal of Applied Genetics 48(3), 2007, pp. 189–198