Safety evaluation of vitamin K2 (menaquinone-7) via toxicological tests

This study aims to evaluate the safety of MK-7 produced by fermentation process using a Bacillus subtilis var. natto strain for human ingestion via acute oral toxicity, repeated dose 90-day oral toxicity, 28-day recovery test, and genotoxicity tests. The acute oral toxicity test results indicated that all subjects survived at the dose of 5000 mg/kg with no toxic effects. For the repeated dose 90-day oral toxicity test, MK-7 was administered to rats at 500, 1500, and 4500 mg/kg for 90 d. No abnormal findings were detected in clinical observations or in clinical pathological and histopathological examinations. The no-observed-adverse-effect level(NOAEL) was determined to be 4500 mg/kg/d, the maximum dose tested. For the evaluation of genotoxicity, reverse mutation, chromosomal aberration, and micronucleus tests were performed. In the reversion mutation test, vitamin K2 did not induce reversion in bacterial strains, and no chromosomal abnormality was observed in the chromosomal abnormality test using Chinese hamster lung cells. In the micronucleus test, micronuclei were not induced using ICR mouse bone marrow cells. All the toxicity test results suggest that vitamin K2 produced by fermentation processes using Bacillus subtilis var. natto induced no toxicological changes under the experimental conditions.