Natto

This is crucial for longevity: vitamin K2 activates matrix Gla-protein to prevent arterial calcification and osteocalcin to direct calcium into bones. A 2025 meta-analysis in Frontiers in Nutrition confirmed that habitual natto consumption elevates serum MK-7 concentrations by 80% and preserves bone mineral density in postmenopausal women and elderly men. Beyond K2, natto contains nattokinase, a serine protease with fibrinolytic activity—a double-blind RCT of 30 adults found it improved bowel movement frequency by 40% over 4 weeks. Its Bacillus subtilis spores survive gastric acid and colonize the lower GI tract, unlike Lactobacillus strains in yogurt that transit without establishing residence. Nutritionally, 100g provides 19g complete protein, 8.6mg iron, and 217mg calcium. Prioritize this for postmenopausal women or those seeking highest natural K2 intake, but consult a physician if on anticoagulants.