Unusually High Enrichment of Bioactive Components for Healthy Aging and Longevity in Natto, a Fermented Soybean Food

Natto is a traditional Japanese food made from fermented soybeans and is a side dish, popular in eastern and northern Japan. Recent studies have suggested a notable link between natto consumption and reduced mortality rates, alongside increased resilience to various stressors and diseases in both humans and model organisms, such as the nematode, Caenorhabditis elegans. Natto is rich in four bioactive components for healthy aging and longevity: bacterial vitamin K2 (menaquinone-7), which supports cardiovascular and bone health; spermidine, known for promoting autophagy and providing anti-inflammatory benefits; the probiotic Bacillus subtilis, which enhances gastrointestinal health; and isoflavone, a plant estrogen. Although there is no officially recommended value set for each component, one serving of natto (50 g) provides significant quantities of vitamin K2 (429%), probiotics (200%), spermidine (625%), and isoflavones (73%) compared to the effective dose in clinical trials and research experiments. Clinical studies have shown no adverse effects of regular natto consumption in healthy individuals, indicating its potential benefits when integrated into a balanced diet. However, caution is advised for individuals with specific health conditions, such as bleeding disorders, soybean allergies, or opportunistic infections, making it essential to consider personal health before incorporating natto into their diet. Taken together, natto has outstanding properties as a food, not only with its bioactivities but also its ability to induce phytohormesis (plant-induced hormesis). This review critically examines the benefits of natto in promoting healthy aging and longevity.