Yucca is a genus of about 40 plus species in the Agave family (Agavaceae) which grow in warm and dry areas of Central America, North America and the West Indies. When discussing the health benefits, it is first important to distinguish between Yucca and Yuca, two common names referring to very different plants. Confusion between the names of the two plants are common, as Yucca is well known in the US, especially in central and western states. Yucca has been used as a folk remedy for the treatment of arthritis and rheumatism, as well as for the hair and scalp, and for its high content of saponins.
   Yuca root (also commonly known as manioc, cassava, or mandioca) has the appearance of a long and tapered sweet potato. It has a rough brown rind on the outside, with an inside that is starchy and can range in color depending on variety from white to yellowish to brown. Yuca plant is widely grown and consumed in Africa, Asia, and the Caribbean. In many countries, yuca is a dietary staple usually eaten boiled, steamed, and in flour form as thickeners or additional ingredients for noodles, cakes, and pastries. Yuca is similar to a potato, but has much more of a waxy and fibrous quality.
   Yucca supplements are available in various forms including liquid, powder, and capsules, especially from the species, Yucca schidigera. Yuca supplements, on the other hand, are also available, but for different purposes, such as a Buffered Vitamin C Powder made from the root, or as a starch for fillers in dietary supplement capsules or use in food products.

Human studies
I could find only one research paper regarding the medical uses of this root as of Feb 2012.

Benefit of yucca plant
There's very little medical research done with the yucca plant. Since yucca has a lot of fiber, it could potentially be helpful in reducing cholesterol levels. Yucca root has phytosterols. Some in vitro studies indicate yucca extract has anti-inflammatory and anti-oxidant qualities. Learn about the health benefit of various vegetable products and their practical interpretation.

Cholesterol reduction
This study was undertaken to observe the effects of the blend of partially purified Yucca schidigera and Quillaja saponaria extracts on cholesterol levels in the human's blood and gastrointestinal functions, and to determine if a new cholesterol-lowering drug can be developed by the further purification of the extracts. Ultrafiltration and sequential diafiltration increased the amounts of steroidal saponin in aqueous yucca extract and terpenoid saponin in aqueous quillaja extract from 9% and 21% to 17% and 61%, respectively. Taking 0.9 mg of the blend (6:4, v:v) of the resulting filtrates a day for 4 weeks resulted in the decreases in total and LDL cholesterol levels in blood plasma of hyper-cholesterolemic patients with enhancement in gastrointestinal symptoms of patients. Arch Pharm Res. 2003. Hypocholesterolemic property of Yucca schidigera and Quillaja saponaria extracts in human body. Division of Endocrinology & Metabolism, Department of Medicine, Miz Medi Hospital, Seoul, Korea.

Yucca Recipe
Yucca root can be boiled and then flavored with herbs and olive oil for a delicious yucca root recipe and a high fiber treat. Yucca root is sold in many grocery stores but it is not very popular. I have a yucca recipe which involves mixing olive oil with zaatar, and then adding that to boiled yucca root. I do remove the skin from the yucca root before adding the mixture. You can also boil yucca root and then cut it in small pieces and add it to soups.

Yucca Flower
Alexin is an antifungal steroidal glycoside extract from Yucca gloriosa flowers.

Species
Yucca aloifolia
Brevifolia, Joshua tree
Elephantipes
Filifera, also known as St. Peter's Palm
filamentosa
Gloriosa flowers have a steroidal glycoside compound called alexin which has antifungal activity.
Yucca schidigera is a medicinal plant native to Mexico. Yucca plant is a source of steroidal saponins, and is used commercially as a saponin source. Yucca is also a source of polyphenolics, including resveratrol and a number of other stilbenes (yuccaols A, B, C, D and E). Yucca schidigera has a very high level of saponins and phenolic compounds with antioxidant action. The products of Yucca schidigera are used as food additives, cosmetics and in the pharmaceutical industry. The bark from this yucca species has phenolic compounds called trans-3,4',5-trihydroxystilbene ( trans-resveratrol ), trans-3,3',5,5'-tetrahydroxy-4'-methoxystilbene, and yuccaols A and C that have antiplatelet activity.
Yucca valida

Yucca schidigera review
Anti-inflammatory and anti-arthritic effects of Yucca schidigera: a review.
J Inflamm 2006. Department of Animal Sciences, Oregon State University, Corvallis, OR, USA.
Yucca schidigera is a medicinal plant native to Mexico. According to folk medicine, yucca extracts have anti-arthritic and anti-inflammatory effects. This yucca plant contains several physiologically active phytochemicals. It is a rich source of steroidal saponins, and is used commercially as a saponin source. Saponins have diverse biological effects, including anti-protozoal activity. It has been postulated that saponins may have anti-arthritic properties by suppressing intestinal protozoa which may have a role in joint inflammation. Yucca is also a rich source of polyphenolics, including resveratrol and a number of other stilbenes (yuccaols A, B, C, D and E). These phenolics have anti-inflammatory activity. They are inhibitors of the nuclear transcription factor NFkappaB. NFkB stimulates synthesis of inducible nitric oxide synthase (iNOS), which causes formation of the inflammatory agent nitric oxide. Yucca phenolics are also anti-oxidants and free-radical scavengers, which may aid in suppressing reactive oxygen species that stimulate inflammatory responses.

Yucca drink
There is an alcoholic drink called Yucca that is made of lemons, limes, sugar, vodka, and ice.

Questions and emails
Q. Is a yucca supplement available?
   A. Yes. Yucca supplements are sold as a root capsule or yucca liquid extract.

Q. I like Yucca, Boniata, Jicama, and Malanga. Could you tell me about glycemic load in each of those product comparing to regular potato.
   A. I am not aware of such studies.

Q. I'm a doctor. I live in Hungary. I deal with the desert herb, Yucca schidigera active agents effects on the human organism since 12 years. Could You please help me to find the answer on my following questions. Have you any documents about Yucca saponins positíve effects? Have you any documents about Yucca saponins side effects? How much resveratrol is in 1 gram Yucca schidigera pulver? Have Yucca saponi effects estrogen effect?
   A. A limited human study with yucca schidigera indicates it may lower cholesterol levels.

I bought a yucca root powder that had an off-white color while the powder from another source had a light brown color?
   Yucca root powder is made from Yucca Filamentosa. The inner part of the root has a white color while the outer part has a brown color. some companies use the inner part of the yucca root which tends to have an off-white color while others use the whole root (inner and outer parts). the inner part of the root has a higher content of saponins.

I just started today to take yucca root capsules 500mg. The instructions read 2 capsules bid or tid. Can you tell me what you think? Can you also tell me how long it takes before you start to feel any benefit from this yucca root capsule. I thank you for any and all information you can give me.
   There are many factors involved including the species of yucca, the quality of the manufacturing process, etc. Having seen few human studies it is difficult for me to predict.