Purple yam or greater yam, among many other names, is a species of yam(a tuber). The tubers are usually a vivid violet-purple to bright lavender in color (hence the common name), but some range in color from cream to plain white. It is sometimes confused with taro and the Okinawa sweet potato (Ipomoea batatas
cv. Ayamurasaki), although D. alata
is also grown in Okinawa where it is known as beniimo
. With its origins in the Asian tropics, D. alata
has been known to humans since ancient times.
Purple yams are cylindrical and rounded at the ends and differ in size and shape depending on the growing environment. They may be twisted or gnarled and can measure up to 20 centimeters long and 8 centimeters wide. The rough skins are brownish-gray and can be covered in small rootlets. The flesh is bright lavender and has a slimy texture like taro and is very starchy. Ratalu Purple yam has a slightly sweet, nutty flavor.
Although available as a dietary supplement and used in folk medicine to treat menopause, osteoporosis, rheumatoid arthritis, infertility, or as an aphrodisiac, there is no clinical evidence that urple yam
has any therapeutic properties. Use of purple yam supplements may have adverse effects in people taking estrogens, anticoagulant drugs or during pregnancy and breast-feeding. Some people may have allergic reactions to use of urple yam supplements. Purple yams are a good source of carbohydrates, copper, vitamin B6 and C, and potassium. They also contain folate, calcium and protein, as well as calcium, iron, phosphorus, and a small amount of vitamin A. The deep purple pigment is the result of anthocyanin compounds which provide antioxidant benefits.