Association Between <scp>D</scp> ‐amino Acids in Natto (fermented soybeans) and Kidney Dysfunction

ABSTRACT In this study, we examined clinical and cohort data to explore the potential renoprotective effects of natto (fermented soybeans) consumption and its relationship with D‐amino acids. In a clinical study, ten healthy adults consumed one 40‐g pack of natto three times in a single day, and plasma and urine samples were collected 1 h and 24 h after intake. In a 5‐year cohort of 295 adults, natto intake was categorized as none (0 g/day), low (1–10 g/day), middle (11–25 g/day), or high (&gt; 25 g/day). The plasma and urinary D‐alanine levels increased significantly after natto consumption. In the cohort, the adjusted mean annual changes in estimated glomerular filtration rate (eGFR, mL/min/1.73 m 2 ) were −1.41, −0.78, −1.01, and −1.01 for the none, low, middle, and high groups, respectively. Low natto intake was significantly associated with a slower decline in eGFR, although no dose‐dependent trend was observed. No significant differences in gut microbiota diversity or composition were found across intake groups. Natto consumption was associated with increased plasma D‐alanine levels and a slower decline in renal function. Further studies are warranted to clarify the mechanisms underlying these associations.