Protein shakes are popular these days with many people. Shannon Muhs, Registered Dietitian & Wellness Coach at the Shadow Lake Hy-Vee says, “People that I notice purchasing protein powder are adults having a protein-filled shake pre- or post-workout. Adults wanting to lose weight may use a protein shake for a meal replacement or snack—also, bariatric surgery candidates.”

So, as for protein, which “whey” do you go: soy or whey? There is no blanket answer. Both have their advantages. Says Muhs, “Soy protein comes from soybeans, has all nine essential amino acids, which makes it a complete protein. According to food scientists, soy takes longer to digest, and it is harder to digest than whey protein. On the other hand, soy can be a nice alternative for someone that cannot have milk products due to an allergy.”

Muhs adds, “Whey protein is a derivative of milk. Whey also contains all essential amino acids and is a complete protein. Whey has been considered superior to soy protein in aiding with muscle gains after a workout because of how easily it is digested and utilized in the body.

“There is still a lot of controversial information out there about soy protein related to its digestibility and chemical reaction it may lead to in the body,” says Muhs.

“The estrogenic activity from the soy isoflavones involves a whole cascade of events involving all of the reproductive hormones. The implications of these effects on hormones are yet to be determined…This is where dangerous deductions and premature conclusions can turn into controversial messages such as, ‘Soy may cause cancer.’”

It is certainly not a cut-and-dried issue. Muhs adds, “There are many studies that have found soy protein to help decrease the risk for many cancers and decrease tumor growth. There are some studies that have found a negative effect on consuming soy protein with high soy isoflavone content; specifically, negative [for] women with estrogen positive breast cancer. It’s not that the soy is directly causing cancer; it’s that it may be affecting the environment in which the cancer may potentially grow.”

Lastly, Muhs says, “We simply don’t know enough to make a conclusion, but why not be safe and avoid soy if you’ve got a history or family history of breast cancer?”