Promotes energy production Gentle on the stomach Non-constipating Non-GMO and free of gluten, dairy, sugar, salt, and preservatives Iron is a vital trace mineral that is involved in a myriad of biological processes, like oxygen transport and energy production?making it a non-negotiable for any healthy, well-balanced diet. However, iron can have some less than desirable effects on your GI tract, like constipation and stomach upset. The Vitamin Shoppe? brand Comfort Iron? is formulated with ferrous bisglycinate-a chelated form of iron that is non-constipating and gentle on your stomach.