The standard dosage of concentrated yucca saponins is two to four tablets or capsules a day. Yucca concentrate is also available as a tea, with the usual dosage being 3–5 cups a day. Capsules and tablets are commonly sold in doses of 500 milligrams. A bottle of 30, 60, 90, or 100 units costs $6–10 and can usually be found in health food stores.
Since yucca has rarely been studied in a scientific setting, it is not known whether it is safe in children, pregnant or lactating women, or people with a history of severe kidney or liver diseases, heart disease, or cancer. It appears to be nontoxic to other mammals, including such household pets as cats and dogs.
Saponins extracted from yucca plants are generally considered safe when used in traditional doses and forms based on several hundred years of use by Native Americans, both as food and medicine. In recent years, the only reported minor problems are rare cases of diarrhea and nausea. Some people who are sensitive to plant allergens may develop a mild skin rash from contact with yucca sap.
Long-term internal use of yucca extract may interfere with the absorption of such fat-soluble vitamins as A, D, E, and K. As of 2002, however, no interactions between yucca and standard prescription medications have been reported.
Ken R. Wells, Rebecca J. Frey PhD, The Gale Group Inc., Gale, Detroit,