{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,3]],"date-time":"2026-09-03T11:13:32Z","timestamp":1788434012263,"version":"build-2803163510"},"reference-count":47,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2025,11,28]],"date-time":"2025-11-28T00:00:00Z","timestamp":1764288000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Nutr."],"abstract":"<jats:sec>\n                    <jats:title>Objective<\/jats:title>\n                    <jats:p>Natto, a traditional Japanese fermented soybean food, is the richest natural source of menaquinone-7 (MK-7), a form of vitamin K2 involved in osteocalcin activation and bone mineralization. This study aimed to systematically evaluate the effects of habitual natto consumption on serum MK-7 concentrations, osteocalcin carboxylation status, and bone mineral density (BMD) in Japanese populations.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>\n                      We searched PubMed, Web of Science, and Scopus through January 2025. Eligible studies compared habitual natto consumers with low- or non-consumers and reported outcomes for serum MK-7, carboxylated or undercarboxylated osteocalcin (OC\/ucOC), or BMD. Certainty of evidence was assessed using the GRADE framework. Random-effects meta-analyses were performed using Cohen's\n                      <jats:italic>d<\/jats:italic>\n                      and 95% confidence interval (CI).\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>\n                      Six observational and quasi-experimental studies (\n                      <jats:italic>N<\/jats:italic>\n                      = 2,327) met inclusion criteria. Natto intake is associated with significantly elevated serum MK-7 [\n                      <jats:italic>d<\/jats:italic>\n                      = 2.10, 95% CI (1.55, 2.66) after sensitivity analysis removing an outlier], increased OC [\n                      <jats:italic>d<\/jats:italic>\n                      = 0.26, 95% CI (0.08, 0.43)], decreased ucOC [\n                      <jats:italic>d<\/jats:italic>\n                      = \u22120.50, 95% CI (\u22120.74, \u22120.26)], and modestly greater BMD across sites [\n                      <jats:italic>d<\/jats:italic>\n                      = 0.65, 95% CI (0.09, 1.21); sensitivity analysis:\n                      <jats:italic>d<\/jats:italic>\n                      = 0.35, 95% CI (0.21, 0.48)]. The certainty of evidence ranges from moderate for serum MK-7 to low or very low for osteocalcin and BMD outcomes, reflecting the predominance of observational designs and remaining imprecision. Publication bias appears minimal.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusions<\/jats:title>\n                    <jats:p>Habitual natto consumption is associated with improved vitamin K status and bone metabolism markers. However, given the observational nature of the available evidence and its moderate-to-low certainty, these findings should be interpreted with caution. Natto may represent a culturally grounded dietary approach for supporting bone health and osteoporosis prevention, but its generalizability beyond Japanese populations warrants further investigation.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.3389\/fnut.2025.1713726","type":"journal-article","created":{"date-parts":[[2025,11,28]],"date-time":"2025-11-28T11:39:07Z","timestamp":1764329947000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":5,"title":["Habitual natto intake elevates serum MK-7 levels, enhances osteocalcin carboxylation, and supports bone density: a meta-analysis of Japanese 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