Methylsulfonylmethane (MSM) is a chemical found in green plants, animals, and humans. It can also be made in a laboratory. MSM has become popular because of the book The Miracle of MSM: The Natural Solution for Pain. But there is little published scientific research to support its use. Contrary to some literature that promotes MSM, there is no Recommended Dietary Allowance (RDA) for MSM or sulfur, which is in MSM. Sulfur deficiency has not been described in the medical literature.