Sodium stearyl fumarate is a food additive commonly used as a flow agent in the production of dietary supplements and powders, including protein powders. It is made from the esterification of fumaric acid and a combination of stearyl alcohol and sodium. Sodium stearyl fumarate is used to prevent ingredients in the powder from clumping together and to improve the powder's flow properties. This helps to ensure that the final product is consistent in texture and easy to mix.
Sodium stearyl fumarate is considered safe for use in food and dietary supplements. The FDA has classified it as Generally Recognized As Safe (GRAS). However, as with any food additive, some people may be sensitive to it and experience adverse reactions such as gastrointestinal upset or skin irritation.