Ester-C® is exclusively formulated for Solgar® and provides an extensively researched, non-acidic vitamin C that is gentle on the stomach. Once taken. • Vitamin A contributes to the normal function of the immune system • Vitamin B6 contributes to the normal function of the immune system • Vitamin C contributes to the normal function of the immune system • Vitamin D contributes to the normal function of the immune system in children.