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Vitamin K Benefits For Osteoporosis: Do You Know What To Look For?

Vitamin K benefits are widely understood in Japan where it is used to prevent osteoporosis. Elsewhere, people are often confused about which vitamin K supplements are best for their situation.

Vitamin K1 is most effective at supporting healthy insulin levels. Vitamin K2 plays a vital role in ensuring that calcium stays in the bones and out of the arteries. It may also protect the heart and inhibit cancer.

Vitamin K was first recognized in 1929 for its vital role in the blood-clotting process. It has now proven effective in the treatment of osteoporosis, heart disease and various forms of cancer.

Both vitamin K1 and K2 have been shown to prevent bone loss but research suggests that vitamin K2 can also contribute to improved bone density (BMD).

The NHANES study has indicated that vitamin K deficiency may be a contributor to the high incidence of osteoporosis in the United States, as seventy-five percent of Americans fail to meet the recommended intake of vitamin K in their diets.

The U.S. Food and Nutrition Board of the Institute of Medicine recommends vitamin K intake of 120 mcg/day for men and 90 mcg/day for women. No Upper Limit (UL) has been established as there are no known cases of vitamin K overdose.

Vitamin K2 supplements are found in two forms: MK-4 and MK-7. Supplement manufacturers argue that while both forms enjoy similar absorption, MK-7 remains in the bloodstream for approximately 72 hours compared to 8 hours for MK-4.

The author of this website is not aware of any published papers that support this claim nor of any research indicating that a longer plasma half-life is beneficial to bone health.

Vitamin K1 Benefits

Vitamin K1 (phylloquinone) is found primarily in green leafy vegetables and makes up about 90 per cent of the vitamin K in a typical western diet.

The research on vitamin K1 indicates reduced fracture risk but not improved bone mineral density (BMD) from higher intakes of vitamin K1.

Nurse's Health Study (>72,000 women over ten years)

  • Women in the lowest quintile (1/5) had a 30% higher risk of hip fracture than women in the higher quintiles (Am J Clin Nutr. 1999;69(1):74-79.)

Framingham Heart Study (>800 elderly men and women over seven years)

  • People taking 250 mcg/day of dietary vitamin K had a 65% lower risk of hip fracture than those taking 50 mcg/day. Bone mineral density (BMD) did not show any improvements. (Am J Clin Nutr. 2000;71(5):1201-1208.)

There is concern that the benefits identified in the Nurse's Health Study and Framingham Heart Study may be related to a healthy diet rather than to vitamin K specifically.

Long-term clinical trials with vitamin K1 supplements ranging from 200-1,000 mcg/day have shown mixed results with respect to improvements in bone density. (Calcif Tissue Int. 2003;73(1):21-26; J Bone Miner Res. 2007; 22(4):509-519; J Clin Endocrinol Metab. 2008;93(4):1217-1223)

Vitamin K1 supplements did not appear to improve bone mineral density (BMD) in older people who were already taking vitamin D and calcium supplements. (J Clin Endocrinol Metab. 2008;93(4):1217-1223.)

Vitamin K2 Benefits

Vitamin K2 is actually a group of compounds known as menaquinones or MK-n. MK-7, MK-8, and MK-9 are found in fermented food products like cheese and natto, a popular fermented soy product found in Japan. Natto is a particularly rich source of MK-7.

In Japan, MK-4 has been an approved medication for osteoporosis since 1995. MK-4 is not found in significant amounts in the North American diet, but it can be synthesized in small amounts by humans from vitamin K1 (phylloquinone) and also from menadione, a synthetic form of vitamin K present in animal feed.

The list of foods containing vitamin K2 is much shorter than the list of foods high in vitamin K1.

Research completed on both MK-4 and MK-7 show an impressive contribution both to the reduction of fractures as well as the improvement of bone mineral density (BMD).


In Japan, studies with osteoporotic women using 45mg/day of MK-4 supplements have reported significant reductions in the rate of bone loss. (J Orthop Sci. 2001;6(6):487-492. and Annu Rev Nutr. 1995;15:1-22)

A meta-analysis of seven Japanese randomized controlled trials indicated that MK-4 supplements increased bone mineral density and reduced fracture incidence. The studies indicated lowered risk for vertebral fractures by 60%, hip fractures by 77%, and nonvertebral fractures by 81%. (Arch Intern Med. 2006;166 (12):1256-1261)

A 45 mg/day dose of MK-4 supplements used in a 3-year placebo-controlled study of 325 postmenopausal women also found improved measures of bone strength in the hips compared to a placebo.

DXA scans indicated improvements in bone mineral content (BMC) and femoral neck width (hip width) but not in bone mineral density (BMD). (Osteoporos Int. 2007;18(7):963-972)

Vitamin K2 supplements in the form of MK-4 (45 mcg) cost about 10 cents a tablet or $35 for a year's supply.


Research conducted in Japan has been very encouraging regarding the contribution of MK-7 to improved bone health.

A study of 944 women (20-79 years old) over three years found that dietary natto intake helped to increase bone mineral density (BMD) in the hips of postmenopausal women and slowed the loss of BMD in the femoral neck and the forearm. (2006 American Society for Nutrition J. Nutr. 136:1323-1328, May 2006)

Vitamin K2 in the form of MK-7 (derived from fermented soy or natto) costs approximately 25 cents for a softgel tablet or $95 a year.

Vitamin K Within Calcium Supplements

Vitamin K1 (phytonadione) is sometimes available within a calcium supplement. A year's supply of Puritan's Pride Bone Care costs approximately thirty dollars and includes 120 mcg of vitamin K1.

Anyone who has a heart condition or is taking anti-coagulants (blood thinners) such as Warfarin or Coumadin should only take vitamin K supplements on the advice of a doctor.