Vitamin K has long been known to be critical to blood clotting. More recent studies show that higher intakes may increase bone mineral density and reduce the risk of hip fracture. And low serum vitamin K levels have been associated with atherosclerosis.
But ConsumerLab.com found that many vitamin K supplements do not contain the listed amount of ingredient. Tests showed that four products provided only 52.5% to 69.9% of the vitamin K stated on their labels -- one of which was also short on calcium.
You must subscribe to get the full test results and ConsumerLab recommendations. In this comprehensive report, you'll discover:
- Which products failed testing and which passed -- including vitamin K-only supplements as well as vitamin K combinations with vitamin D and/or calcium
- The large differences in potency among vitamin K1 and the two forms of vitamin K2 now sold -- menaquinone-4 and menaquinone-7 (MK-4 and MK-7)
- Dosages used for specific uses with specific chemical forms
- Concerns and cautions -- and how one form of vitamin K may interfere with blood thinners at a much lower dose than other forms
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See separate reports on Calcium Supplements and Vitamin D Supplements.
