Konnyaku is a bland gelatin-like food. There was a lovely bowl of the gray speckled starch, flavored with soy and sesame, at breakfast in our hotel in Tokyo.

I thought it tasted faintly of taro. My wife said, no, it tasted of rice flower. It contains neither. Some web sites say it is made from konnyaku potatoes or sweet potatoes. Not exactly. It is made from konjac, also known as dragon’s tongue. Konjac doesn’t look like any type of potato, and is unrelated to potatoes or yams.

The konjac is dried and made into a flour, mixed with lime water, and steamed in a mold to make flat blocks of konnyaku. Konnyaku is 97% water and has a lot of fiber. (Note that cucumber is 96% water.) It is often cut into cubes or sliced into noodles. Advocates proclaim it to be a great health food.

So when may you have eaten konnyaku without knowing it? Those fruit-flavored cubes of jelly sold in small cups were made with konnyaku, not gelatin. Not being gelatin, they don’t melt in the mouth and have to be chewed. As a consequence they were identified as a choking hazard for small children, and have now mostly been taken off the market.

As a breakfast food, I think corn flakes have little to worry about. But it’s good for you.