The reason that your body needs to have threonine is that it is used to help maintain the proper balance of protein in your body, without it you can end up with too much or too little protein. Threonine is also need to help your body form collagen and elastin, which is needed to keep your skin healthy. Threonine is also needed to ensure that your liver is functioning properly, it helps fight fatty liver. Threonine also helps the immune system because it helps produce antibodies, as well as promoting thymus activity and growth.
One thing that you want to think about with threonine is that other nutrients are better absorbed by your body if threonine is present, so having it in your daily diet is truly beneficial. While there is, no serious side effects associated with taking too much threonine you do want to avoid not getting enough. If you suffer from a threonine deficiency, you can become a difficult person to get along with because of how irritable you are.