The Deal with Eel

After the rainy season comes to an end around the middle of this month for most of Japan, the summer that follows tends to be pretty pitiless. As that season cranks into gear, thermometer and hygrometer levels signal a humid heat that feels positively tropical, and the nation as a whole just wilts. Back in an age before people could enjoy the refreshing luxury of air-conditioning, the Japanese developed various strategies to beat the summer heat. They related ghost stories on summer nights for their appropriately chilling effect, and they hung up small wind chimes, whose tinkling sound offered a little psychological cooling respite. And they also took to stuffing themselves on eel.

The story has it that one summer in the late 1700s, a restaurant in Edo, as Tokyo was formerly known, was having rather a hard time of it. The restaurant specialized in grilled eel, and in the sweltering summer heat and humidity, people in the neighborhood seemed to prefer lighter foods over the rich serpentine fish. The grilled-eel shop owner fell into financial difficulties, and so he sought the advice of a neighbor, the famous writer and pharmacologist Hiraga Gennai. On hearing about the situation, Hiraga took up his writing brush and created a sign for the restaurant owner to hang outside his establishment. The sign read “Grilled Eel on the Day of the Ox,” that day having been taken from the zodiacal calendar of the East. This association of eating eel with the Day of the Ox was entirely Hiraga’s invention, but the people of Edo were apparently curious to try it out. Other restaurants latched on to this remarkably good marketing scheme, and so gradually the custom spread of eating grilled eel on the bovine day in July to help maintain flagging staminas. [Ed. Midsummer Day of the Ox in 2021 is July 28.]

The Ooedo eel restaurant, located close to the site of the former Nihonbashi fish market, has been in business since around 1800. JAPAN JOURNAL PHOTO

All eels are spawned in the sea, but since Japanese eel migrate to rivers and lakes, where they grow and mature, they tend to be regarded as freshwater fish. Eels naturally have a slightly muddy taste, and so in Japan they were originally served flavored with miso and sprinkled with fragrant sansho (Japanese pepper) to mask the unattractive flavor. 

During the Edo period (1603–1867), living standards rose and eating habits improved. After a major fire in 1657 destroyed nearly two-thirds of Edo, laborers from all over the country flocked there to rebuild it, and a food-service industry flourished. Street vendors sold such delicacies as sushi and tempura, and many of today’s favorite dishes were refined during that period. Previously, most of Edo’s culture had been taken from Japan’s imperial capital of Kyoto, but by the late 1700s an original Edo food culture began to blossom.

One typical Edo dish that developed was unagi kabayaki, or broiled eel. A new technique was devised to improve on the original miso-flavored eel. It involved steaming the eel, then grilling it afterward while basting it with a mixture of soy sauce, sake and mirin (a sweet liquid flavoring). Cooking the eel in this fashion gives off an appetizing aroma, and the grilled fish can be eaten simply on its own or served on rice.  

Unagi kabayaki, split eel broiled in a sweet soy-based sauce, is an Edo-period classic. The dish is popularly eaten in July to help provide vigor in the summer heat. JAPAN JOURNAL PHOTO


The original idea of eating unagi kabayaki on the Day of the Ox in July may have been a rather deft promotional effort, but there is in fact a nutritional basis for consuming the slippery fish at the height of summer. Because people do a good deal of sweating in the hot weather, they tend to lose water-soluble vitamins and minerals. And eel happens to be rather rich in both those nutrients.

There is also an ancient basis for eating eel in the dog days, and the magnificent eighth-century poetry collection of the Man’yoshu refers to consuming eels then. Otomo Yakamochi may have been a great poet and statesman, but he certainly didn’t think it was beneath him to ridicule one Iwamaro. Iwamaro had the kind of constitution most supermodels would give their eyeteeth for — he could eat and drink prodigiously but always managed to look emaciated. And in those pre-Twitter times, Otomo poked fun at the man in verse:

Iwamaro, I tell you, catch and eat eels.

That is sure to work if you’ve 

slimmed down in the summer. 

David Capel is a journalist living in Tokyo.

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