Does Your Vitamin D Supplement Need To Have Vitamin K2 In It, Too?

Some things in life just seem to pair together naturally—peanut butter and jelly, coffee and quiet mornings, you get the gist. Another one of these natural power couples (or at least so you might think): vitamin D and vitamin K.

These two nutrients are each incredibly important for your health in their own right—and if you've seen them packaged together in supplements, you've probably wondered: Do I really need to take these two vitamins together?

Though you've probably heard loads about vitamin D and its many benefits by now, vitamin K doesn't always get its fair share of the spotlight. (Maybe you've heard that it's important for blood-clotting—but that's probably it.*)

Wondering what this whole vitamin K2 thing is about? Two forms of vitamin K2 exist in the body. Vitamin K1 (aka phylloquinone) and vitamin K2 (aka menaquinone). We primarily get vitamin K1 from green leafy vegetables and transport it to the liver. Meanwhile, K2 can be found in fermented dairy and is also naturally produced by the lactic acid bacteria in our gut. It's this form—K2—that has been studied for its connection to bone and cardiovascular health3, among other things.*

If you're wondering what this all means for your supplement routine, right now, well, the answer is not much.

"Some companies offer vitamin D3 and vitamin K2 combination supplements, and that's fine," says mbg director of scientific affairs Ashley Jordan Ferira, Ph.D., RDN. "They are simply two of the four fat-soluble vitamins our body needs, though, and the direct combination of them in supplements has nothing to do with their absorption; that's a misconception." (Vitamin D is required for calcium absorption, hence why you'll almost always find some necessary vitamin D in calcium supplements.)*

In many cases, fat-soluble vitamins are combined together in supplements for convenience, according to Ferira, who says that supplement complexes containing all four fat-soluble vitamins are also found in the market, including in a high-quality, comprehensive multivitamin.

Ultimately, though, pairing vitamin D and vitamin K2 together in a supplement doesn't affect the absorption or bioavailability of either, Ferira says, urging that "there is no science to back such a proposition."

While there's no harm in supplementing with vitamin D3 and vitamin K2 together, doing so certainly isn't necessary and doesn't affect your absorption of either nutrient. However, since both promote cardiovascular and bone health, you might find them (potentially among other ingredients) in a complete multivitamin or targeted multi-nutrient formulas created to support your bones and cardiovascular system.*