Everything on life is composed of matter. Even the air we breathe is matter. The laptop that I am typing this from is matter. All life is composed of matter in some way shape or form. This is something that is well known and is not questioned by anyone that knows it.
Matter is defined as "physical substances" and that is what our bodies are made up of. Our bodies are built out of matter that was once in stars, and our lives are emergent properties of the particular arrangements of that matter. Unless someone is going to claim that our bodies are immaterial, I don't see how you can say that life is not composed of matter.