“No adverse effects observed”: CRN confirms vitamin K2 safety at high intake level

The Council for Responsible Nutrition Foundation (CRN) has updated its safety guidance for the highest observed intake (HOI) level for vitamin K2, specifically in the form of MK-7, at 375 µg/day for adults.

Previous editions of CRN’s Vitamin & Mineral Safety provided a single Upper Limit (UL) value for vitamin K, encompassing vitamin K1 and vitamin K2.

The UL and HOI for vitamins are determined by identical risk assessment procedures. However, CRN explains that a UL is set for nutrients that pose adverse effects after a designated high intake level, while an HOI is the highest intake level at which no adverse effects are observed.

Scientific evidence supports MK-7’s role in supporting bone and cardiovascular health. CRN observes this has contributed to the “rapidly expanding” global consumer interest and use of vitamin K2 supplements, which prompted this separate assessment.

“CRN’s updated MK-7 chapter reflects our commitment to providing rigorous, transparent safety evaluations grounded in the totality of evidence,” says Andrea Wong, senior vice president, scientific and regulatory affairs at CRN.

“Establishing a HOI for vitamin K2 (MK-7) represents a major step forward for scientific understanding and responsible product development across the dietary supplement category.”

The updated vitamin K2 guidance is published in the 4th edition of CRN’s Vitamin & Mineral Safety (VMS4), which incorporates “modern methodology, expanded human clinical evidence, and new global regulatory perspectives.”

Supporting clinical data

The new guidance summarizes reviews of more than 40 human clinical trials conducted over the past decade. CRN evaluated vitamin K2 doses ranging from 58–462 µg/day for timeframes up to two years.

Among these trials for vitamin K2, researchers observed no serious adverse effects related to MK-7. Studies also consistently demonstrated no clinically meaningful impact on coagulation parameters in individuals not taking vitamin K antagonist medications, commonly known as blood thinners, such as warfarin.

Based on these findings, CRN outlines 375 µg/day as the HOI for supplemental MK-7 in adults. This HOI does not apply to individuals using VKA anticoagulants, who should consult their healthcare providers before using vitamin K-containing supplements.

In addition to vitamin K2’s benefits in bone and heart health, scientific studies highlight other potential benefits, such as alleviating long COVID symptoms, conditions related to poor kidney function, and women’s health during menopause.