Solaray, Slippery Elm, 400 mg, 100 VegCapsNon GMO 100% Vegan Dietary Supplement Ulmus Rubra 400 mg Per Capsule Whole Bark Lab Verified Discussion: Native to North America, Slippery Elm is a species of Elm tree with a long history of use in herbal medicine. Slippery Elm bark is high in a soluble fiber known as mucilage, a thick, gelatinous substance. Studies suggest that Slippery Elm bark may provide nutritive support for gastrointestinal wellness and healthy respiratory tract function.