Edogawa-ku, Tokyo is one of the largest producers of komatsuna, a form of Japanese mustard spinach.  Komatsuna was named after a place in Edogawa, "Komatsugawa" by Yoshimune Tokugawa who is the eighth shogun of the Tokugawa shogunate.

Edogawa ward, Edogawa Farmer's club, Edogawa Horticulture Association and Hirosaki University has researched into the taste and functionality of komatsuna. Pigment composition of komatsuna contains neoxanthin, a kind of carotenoids. According to research, neoxanthin might be able to prevent obesity. The study shows that the activity of an enzyme which relates to the composition of fat decrease and accumulation of fats is controlled when add the neoxanthin to a cultured adipocytes.

Sometimes an infection of nitrates which is contained in raw leafy vegetables is pointed out. However, komatsuna which produced in Edogawa, has proved that the amount of nitrates is less than the reference value. Also, the safety of the komatsuna, which is grown in Edogawa, is demonstrated through Animal experimentation.

Additionally, Sarada-komatsuna, which is also from Edogawa,  is recommended. It can be eaten without heating and so you can ingest vitamins and carotenoids more efficiently.