Vitamin K
Phylloquinone (K1) and menaquinones (K2)
Vitamins. Modern nutrition.
Also called Phylloquinone, Menaquinone-4 (MK-4), Menaquinone-7 (MK-7)
Pinyin: wéishēngsù K
Spanish: Vitamina K
Interferes with warfarinA fat-soluble vitamin needed for blood to clot and for proteins that keep bones and blood vessels healthy.
Did you know? Vitamin K is named for the German word Koagulation, meaning clotting. Danish scientist Henrik Dam found it in chicks that bled easily, and he shared a Nobel Prize in 1943.
What it may help, and how strong the proof is
- Anemia & blood building. Vitamin K is needed to make proteins that help blood clot. Low vitamin K causes bleeding, which is why newborns get a vitamin K shot after birth. Vitamin K corrects deficiency in people who are low.Strong proof
- Bones. Vitamin K2 helps bone proteins hold calcium. Some trials in Japan found fewer fractures with K2, but other trials found little effect, and larger trials are lacking.Early proof
Parts of the body
Traditional use
Japanese diets have long included natto, fermented soybeans rich in vitamin K2. European diets with leafy greens and aged cheeses also supplied vitamin K for generations.
How it is classified
- Herbal actions
- Nutritive, Hemostatic. Energy: neutral.
How people take it
Adequate intake (AI), used when no RDA is set, is 120 mcg a day for men and 90 mcg a day for women. No upper limit has been set for vitamin K from food or supplements. Bone trials in Japan used 45 mg a day of MK-4, a much higher dose.
Food, tablet and capsule.
Where to get it
Good sources of K1 are cooked kale, collard greens, spinach, broccoli, Brussels sprouts, parsley, and soybean or canola oil. Natto is the richest food source of K2 (MK-7). Egg yolks, chicken liver and some cheeses also contain K2 (MK-4). Pills are usually K1 or MK-7.
Be careful
Vitamin K from food is safe. It changes how warfarin works. People on warfarin should keep vitamin K intake steady rather than avoid it, and should not start or stop supplements without a doctor. Rarely, the newborn injection causes an allergic reaction.
Avoid if: taking warfarin (check first).
Mixing with other things
- Works well together
Vitamin K helps direct calcium into bone. The evidence is still developing.
- Works well together
Vitamin K2 helps bone proteins bind calcium.
- Don't mixBlood thinners (warfarin, Eliquis, Xarelto, Plavix, daily aspirin)
Vitamin K directly works against warfarin and similar blood thinners. Do not start or stop supplements without medical advice.
- Worth knowingAntibiotics (doxycycline, Cipro and similar)
Long antibiotic courses can reduce the vitamin K made by gut bacteria.
Found in these formulas
Bone trio (Modern)
The honest take
Vitamin K is essential for clotting, and deficiency is serious for newborns and people with fat-absorption problems. Vitamin K2 may help bones, but trial results are mixed. Claims that K2 prevents heart disease or reverses artery calcium are not proven.