Can Wild Yam (dioscorea villosa) replace Yamaimo (d. japonica) in japanese cuisine


Yamaimo (dioscorea japonica) or Nagaimo (dioscorea polystachya) is used in many places in Japanese cuisine — be it topping for Zaru-Soba together with Negi, or the ubiquitous Okonomiyaki.

Where I live, both are unobtainable, be it powdered, canned or fresh. So I have to look for an alternative. As many genuine Yamaimo/Nagaimo powders are expensive, I looked for alternatives.

It seems only “Wild Yam”, dioscorea villosa, is available as powders. Origins seem to be Mexico, Ghana or Indonesia, most of the times.

The interesting question is: Are cooking properties, especially the “slimey” and viscous texture, similar enough to Yamaimo/Nagaimo, that it can be used as a emergency-substitute?

Best Answer

I would recommend against using Dioscorea villosa as a substitute for either yamaimo or nagaimo. I would also recommend against using any commercial product coming from Ghana, Mexico, or Indonesia which claims to be Dioscorea villosa.

The reason for my recommendation comes not from direct experience, but from my general knowledge of biology and taxonomy. Many members of the yam family are toxic to humans; or, if not harmful outright, may have medicinal properties (remember the rule that even good medicine is poison at the wrong dosage). There are also, of course, many edible yams; but each species is very different, and Dioscorea villosa has a reputation as a medicinal yam based both on tradition and on its diosgenin content, for which it was at times throughout history exploited for the biochemical production of steroid hormones (diosgenin can be chemically converted into steroid hormones). You should be VERY cautious before consuming culinary-quantities of a potentially-medicinal product.

Moreover, I am very skeptical of the idea that commercial products from Ghana, Indonesia, or Mexico truly are derived from the species Dioscorea villosa. They mention the diosgenin content quite prominently; many wild yams all around the world have been harvested (and over-harvested) for their diosgenin content. These wild yam powders are probably meant as medicine, possibly with extraction or filtration to increase diosgenin content.

Dioscorea villosa is native to the temperate regions of eastern North America. As a species I do not affirmatively know that it can even withstand the tropical climates of any of those countries. Wild yams native to the countries you name have indeed been used medicinally for thousands of years, but the particular Latin name "Dioscorea villosa" does not apply to all wild yams. It applies only to the particular North American species whose common name is "wild yam", other species whose common name is "wild yam" have other Latin names.

Thus, even if you were to buy one of these Dioscorea villosa powders, you would be wise to try to track down where the plants were harvested, so that you are more likely to know what species it actually comes from. If they weren't harvested in the Eastern US, or at barest minimum in a similar temperate climate, they probably weren't really Dioscorea villosa (there was probably a mistake in species-naming). It is typically unwise to put unknown substances into the body, and that's all the more true given the large differences between Dioscorea species.