Nattō, a traditional Japanese dish made from fermented soybeans, is gaining attention in Western countries for its potential health benefits, including its role in lowering blood pressure and improving bone health. While popular in Japan for centuries, its distinctive pungent aroma and slimy texture make it a polarizing food.
Historically introduced to Japan around the 700s and later becoming a staple by the Edo period (1603–1867), nattō is made by soaking, boiling or steaming soybeans and fermenting them with bacteria. Traditionally, this was done by wrapping the beans in straw, but modern production often uses controlled fermentation. Today, it is readily available in Japanese supermarkets and online, typically costing around £5 for a 100g package. It is usually eaten cold, often with a packet of soy sauce and hot mustard.
A 50g serving of nattō is low in calories (110) and provides about 10g of protein, virtually no salt, and 5.4g of fiber. It is also rich in micronutrients such as calcium, potassium, iron, manganese, vitamin K2, vitamin B6, and vitamin E. These nutrients are associated with benefits for bone health, blood circulation, skin elasticity, and oral health. London-based dentist Dr. Soumaya Zinet notes that nattō is particularly rich in MK-7, a form of vitamin K2, which is essential for normal blood clotting and maintaining bone health. The fermentation process also produces nattokinase, an enzyme studied for its potential role in breaking down fibrin, a protein found in blood clots.
Research suggests that nattō can contribute to heart health, stronger bones, and reduced blood pressure. Clinical studies indicate that nattokinase may help dissolve blood clots and support healthy circulation. A 2022 study from Pakistan suggested that consuming nattō could aid in managing high blood pressure. Furthermore, a 2020 study published in the British Medical Journal, involving researchers from the National Cancer Center in Tokyo, found that individuals who regularly consumed fermented soy products like nattō saw a 10% reduction in their risk of death from stroke or heart attack. The high levels of vitamin K2 in nattō have also been linked to improved bone mineral density and reduced fracture risk in postmenopausal women. According to Dr. Zinet, the calcium and phosphorus content in nattō, along with vitamin K, supports overall bone health, which in turn benefits the teeth.
Despite its potential benefits, nattō is not suitable for everyone. Individuals with a soy allergy must avoid it, and like other beans, it can cause temporary bloating or gas. The primary medical concern is for those taking anticoagulant medication, such as warfarin, or other vitamin K antagonists. Because nattō is very high in vitamin K, it can interfere with these medications. An excess of vitamin K can lead to liver problems, breathing difficulties, and issues with blood clotting. Therefore, individuals on such medications should consult their doctor before significantly increasing their nattō intake. Additionally, due to its sticky nature, nattō can be difficult to remove from dental appliances like braces, making thorough rinsing and cleaning after consumption important.
