For the secondary outcomes, MNP supplementation increased hemoglobin concentration (MD 1.85 g/L, 95% CI 1.24 to 2.47; I2 = 85%, p < 0.00001), serum/plasma ferritin (MD 11.08 μg/L, 95% CI 10.58 to 11.58; I2 = 95%, p < 0.00001), and risk of diarrhea (RR 1.30, 95% CI 1.11 to 1.53; I2 = 0%, p = 0.002), and decreased soluble transferrin receptor concentration (MD −0.86 mg/L, 95% CI −1.46 to −0.26; I2 = 84%, p = 0.005), risk of iron deficiency (RR 0.50 95% CI 0.40 to 0.63; I2 = 77%, p < 0.00001), and risk of iron-deficiency anemia (RR 0.45 95% CI 0.34 to 0.58; I2 = 23%, p < 0.00001). The gene discussed is TFRC; the disease is anemia.