Vitamin K is a generic name for a group of three vitamins, namely phylloquinone, or vitamin K1, menaquinone, or vitamin K2, and menadione, or vitamin K3. This vitamin plays a very important role in blood clotting and in the treatment of liver diseases, but according to recent studies, it also influences bone health.
Bone Health and Vitamin K
Postmenopausal women will benefit the most from the effects of vitamin K, as they have a greater risk of osteoporosis. This vitamin prevents bone fractures by increasing the bone density. A proper supplementation of vitamin K decreases the risk of hip fracture by 77%, vertebral fracture by 60% and non-vertebral fractures by 81%. Thus, the higher the intake of vitamin K, the greater the bone density. On the other hand, people who suffer from osteoporosis have been discovered to have lower vitamin K levels. Bones contain three proteins that are dependent of this vitamin, one of the three being osteocalcin, a protein that is produced by the bone-forming cells.
It is a known fact that vitamin D influences bone health, but recent evidence shows that this vitamin is helped by vitamin K to improve bone density. The studies that sustain this were based either on higher doses of vitamin K2 or on lower doses of vitamin K1, administered along with vitamin D.
Besides influencing bone density, vitamin K also plays another major role in bone health. Calcium is known to be a key element in the metabolism of bones, and vitamin K improves calcium balance.
Vitamin K Sources
Even though there are plenty of vitamin K supplements available, you should focus on food as the main source of this vitamin. Some of the foods rich in vitamin K include:
- Brussels sprouts
- Soy beans
- Cow milk
Recommended Daily Amount of Vitamin K
Most of the foods listed above include in a single serving more than just the RDA (Recommended Daily Amounts), which is:
- 80 microg/d for adult men
- 65 microg/d for adult women
- 5 microg/d for newborn infants
However, the Institute of Medicine recommends an intake that is nearly 50% higher than the RDA presented above. More precisely, the dietary reference intake according to this Institute is:
- 120 microg/d for adult men
- 90 microg/d for adult women
This increase appeared as a necessity, as some studies suggested that bone health does not improve when less than 100 microg of vitamin K are administered daily.
While vitamin K1 is found in dietary form, vitamin K2 is synthesized by the bacteria colonies found in the large intestine. Besides that, you need to keep in mind that synthetic vitamin K is twice as potent as the one found in foods. From this point of view, vitamin K supplements are better.
Overdose Risk and Adverse Reactions
Fortunately, high doses of vitamins K1, K2 and K3 are not toxic. However, if you follow a treatment based on anticoagulants such as Warfarin, you are not recommended to take high doses of vitamin K. Because of this restriction, you are recommended to talk to a health care provider before taking vitamin K supplements.