The supplement ingredient called sarsaparilla is usually the dried roots of various species of Smilax. Of these, Mexican sarsaparilla (S. medica), Honduran sarsaparillas (S. regelii and S. officinalis) are the most used. So-called Indian sarsaparilla is of a different genus (Hemidesmus) and is not a true Smilax, having none of the qualities described here. Smilax species contain various amounts of steroid components as well as saponins, resins, starch and a small amount of volatile oils.

The biological activity of sarsaparilla is unknown completely but much of what is attributed to it is probably false. Current advertisements tout the ability of Smilax to increase strength and energy due to the steroid components. Testosterone is not found in sarsaparilla, despite the many claims of its presence. Historically, sarsaparilla was thought to purify the blood, helping to detoxify and rid the body of disease (especially syphilis). This activity is unconfirmed by research.

Sarsaparilla has been shown to increase the absorption of various drugs, especially the drug digitalis. Other activities associated with sarsaparilla are hepatoprotection, diuretic, and antiinflammatory activities. Little is known about the effectiveness of extracting sarsaparilla roots, therefore, whole root preparations are usually used.