Natto fermented soybeans

Natto is soybeans fermented with Bacillus subtilis. Its characteristic smell and stickiness can be a challenge even to some Japanese people, including me. At least I have a natto dish I like -- tempura. Natto's smell and stickiness are controlled by deep-frying, leaving a pleasant sweet aroma and melting texture. Typically, it is eaten with hot steamed rice, often accompanied with a raw egg, a small amount of soy sauce and karashi mustard. Tom likes eating natto this way, and this has impressed a bunch of Japanese people, my parents included.

Personal preference aside, natto has centuries of history -- the oldest record of the name in Japan appears in a 11th century book and the food itself is assumed to have been around hundreds or thousands years earlier than that -- and it is very nutritious, just like other fermented or sticky/slimy food. Natto is rich in Vitamin K (600 μg/100 g), protein and fiber (6.7 g). Its health effects include prevention of osteoporosis (Vitamin K2 promotes bone protein function and bone formation) and reduction of thrombosis (nattokinase, an enzyme, dissolves blood clots). With an antibiotic effect, natto used to be used as medicine for contagious diseases such as dysentery and typhus, and it has been confirmed to be effective against E. coli bacterium and salmonella.

There are dozens of natto brands and products at stores. I cannot tell much difference among them and randomly choose by package design. Natto keeps well in the freezer. To find the best natto at a store, look for someone from the eastern or northern part of Japan -- natto consumption is higher in these regions -- and you will likely get more insightful knowledge.

Those who take warfarin (an anticoagulant) are advised not to eat natto. Nattokinase, an enzyme in natto, is a natural blood thinner. However, natto is high in Vitamin K (345µg/100g), and bacillus subtilis var natto produces Vitamin K in the intestines and could affect thrombotest or International Normalized Ratio (INR). Too much Vitamin K counteracts warfarin, and natto provides a bit too much for the drug to do its job.

200 kcal/100 g; 59.5% water, 16.5% protein, 10.0% fat, 12.1% carbohydrate, 1.9% ash


Recipes with natto

• Tomato to nira no nattojiru / miso soup with fermented soybeans, tomato and garlic chives 
• Nattojiru / miso soup with fermented soybeans
• Natto no tenpura / fermented soybean tempura
• Tofu no chige / jjigae stew with tofu  (quick version with kimchi)

(Last updated: September 7, 2016)