You already know the benefits of vitamin D for building stronger bones, reducing inflammation, and enhancing immunity (especially important right now). And you’re probably taking a daily D—but are you taking it the right way? Some research suggests that vitamin K in combo with vitamin D greatly enhances the sunshine vitamin’s bone-building benefits—and supplementing with just vitamin D if you’re low in vitamin K could even be harmful.
The ABCs of Vitamins D and K
Vitamin K occurs in several forms. The most common is vitamin K1, found in spinach, kale, and other dark, leafy greens, which accounts for 75–90 percent of the vitamin K consumed by humans. Less common is vitamin K2, found in small amounts in animal products and fermented foods. It’s also synthesized by gut bacteria.
In the body, vitamin K is crucial for the normal clotting of blood, and it also plays an important role working alongside vitamin D to form healthy bones.
Vitamin D promotes calcium absorption in the gut and maintains proper blood levels of calcium to meet the body’s needs. But vitamin D alone doesn’t dictate where the calcium you ingest ends up. Vitamin K integrates calcium into bones and teeth, preventing it from being deposited in soft tissues, such as the kidneys or arteries—important, since calcium deposits in the kidneys are linked with kidney diseases, and the buildup of calcium in blood vessels increases the risk of coronary artery disease, heart attacks, and stroke.
Simply Better Together
Studies suggest that vitamins D and K are more effective than either alone in promoting bone health and reducing the risk of osteoporosis. Optimal concentrations of both vitamins D and K, in the right balance, improve bone mineralization, increase bone density, and can reduce the risk of fractures.
And taking vitamin K in conjunction with vitamin D also protects your heart. Research suggests that people with a higher intake of vitamin K have a lower risk of blood vessel calcification and heart disease. In one study, vitamin K supplementation slowed blood vessel calcification, and another study showed a 24 percent higher risk of heart attack in people who took calcium and vitamin D supplements without adding vitamin K.
What to Look for in Supplements
Most research suggests that vitamin D3 supplements are more potent, better absorbed, and more bioavailable than D2 supplements (although one study found that vitamin D2 worked as well as vitamin D3). New vegan vitamin D3 supplements, derived from lichen, are an excellent alternative for anyone who avoids animal products. As for vitamin K:
You’ll find vitamin D and vitamin K supplements in a variety of forms. The basics:
- Vitamin D3 (cholecalciferol), the natural type of vitamin D produced by your body in the presence of sunlight, is the most common form found in supplements. But because it’s made from animal sources, like lanolin from lamb’s wool, it’s not appropriate for vegans.
- Vitamin D2 (ergocalciferol), the form synthesized by plants, isn’t naturally produced by humans. D2 supplements are derived from plant sources, usually irradiated fungus.
- Vitamin K1 (phylloquinone) is abundant in the diet, so unless you eat few leafy greens, you probably get enough.
- Vitamin K2 (menaquinone) is harder to get through dietary sources. Menaquinone is actually a family of compounds, including MK-4 and MK-7, that differ in their biological activity. The MK-7 form is thought to be the most bioavailable, although some products contain a full spectrum of vitamin K2 chains (MK-4, MK-6, MK-7, and MK-9) for a wider range of benefits. You’ll also see MK-7 as MenaQ7, a patented form that has enhanced bioavailability.
When you’re buying a vitamin D supplement, always choose one with vitamin K for the best bone-building and cardiovascular benefits. Look for those with a full spectrum of vitamin K2 chains, or with MK-7. Products that include the enzyme lipase can enhance absorption of these fat-soluble vitamins.