Proteases are enzymes that help to digest proteins. All living organisms depend upon them to maintain normal cellular processes. The proteases in your body are used by cells and the digestive tract to function properly. Because your body produces its own protease, taking protease supplements won't benefit you in any way.
The human body, like every other living organism, needs enzymes to help it engage in chemical reactions in a timely manner. Many reactions take place much too slowly to support life; enzymes help speed up chemical reactions. A particular enzyme can participate in only one type of chemical reaction, explain Drs. Reginald Garrett and Charles Grisham in their book "Biochemistry." For instance, protease enzymes help digest proteins, but can't participate in any other kind of chemical reaction.
It's a common misconception that many diseases and disorders result from enzyme deficiencies, and can be prevented or treated with enzyme supplements. In reality, the human body produces the enzymes it needs to regulate function, and true deficiencies are quite rare. The exception to this general rule is the case of lactase deficiency, which results in lactose intolerance, and is relatively common. Generally speaking, however, enzyme supplements are neither necessary nor helpful in treating and preventing disease.
One of the reasons that most protease supplements aren't helpful is that there's no known mechanism whereby the human body can take up enzymes from the digestive tract into the cells. There is no scientific research to indicate that enzymes taken by mouth have any effect outside the digestive tract. Further, enzymes are proteins, and like all dietary proteins, they're quickly destroyed and degraded by stomach acid, explain Drs. Mary Campbell and Shawn Farrell in their book "Biochemistry."
One possible exception to the general rule that protease supplements have no effect in the body is bromelain, or pineapple enzyme. While research is far from conclusive at this point, there's some indication that bromelain taken orally may have anti-inflammatory effects in the body, explains Dr. H. Maurer in a 2001 article published in "Cellular and Molecular Life Sciences." The mechanism for this is still unknown, however, and Maurer notes that it's likely that much of the noted pharmacological activity of bromelain is due to properties of the molecule rather than its protease activity.