Vitamin K, once thought to be important only because of its role in producing clotting factors, also helps keep bone strong. Low levels of vitamin K may be associated with bone loss characteristic of osteoporosis. Increasing vitamin K levels may help reduce the risk of fractures that can cause significant health problems and increase the risk of death. Study results are mixed; further study is required to determine the role of vitamin K in preventing or treating osteoporosis.
Actions
Vitamin K may have a positive effect on calcium balance; calcium is an essential component of bone. Vitamin K may also play a part in production of osteocalcin, a necessary bone protein. Vitamin D and vitamin K may work together to increase bone mineral density when taken together, researchers from Hoffmann-La Roche Ltd in Switzerland reported in the October 2001 issue of "Nutrition."
Effects
Researchers from Brigham and Women's Hospital and Harvard Medical School examined 1984 data from 72,327 women in the Nurses' Health Study. The results, published in the January 1999 "American Journal of Clinical Nutrition" found that women who had low vitamin K intake were most likely to suffer hip fractures. An increase in lettuce intake, the food most associated with vitamin K intake in the study, to one or more serving per day, decreased the risk of hip fracture.
Supplementation
Several studies on the benefits of supplement doses between 200 and 2,000 mcg of vitamin K have had mixed results. A study conducted by the U.S. Department of Agriculture Human Nutrition Research Center on Aging at Tufts University that gave subjects either 500 mcg per day of phylloquinone, a form of vitamin K, or placebo along with calcium and vitamin D for three years. Results published in the April 2008 "Journal of Clinical Endocrinology and Metabolism" reported that although phylloquinone levels rose and undercarboxylated osteocalcin concentrations, a marker for bone formation, fell, there was no increase in bone density at the spine or hip.
Fracture Effects
Although bone density does not appear to increase in people taking vitamin K supplements, taking the vitamin may reduce the risk of fractures and cancer development, a University of Toronto study published in the October 2008 issue of "PLOS Medicine" reported. A total of 440 were randomized to receive either 5 mg per day of vitamin K or placebo. Over a four-year period, vitamin K levels rose in the treated group and undercarboxylated osteocalcin levels fell. However, the vitamin K group had 9 fractures during that time compared to 20 in the placebo group and three cancers compared to 12 in the placebo group.
References
- "American Journal of Clinical Nutrition;" Vitamin K intake and Hip Fractures in Women: a Prospective Study; D. Feskanich, et al.; January 1999
- "PLOS Medicine;" Vitamin K Supplementation in Postmenopausal Women with Osteopenia (ECKO Trial): A Randomized Controlled Trial; A. Cheung, et al.; October 2008
- "Journal of Clinical Endocrinology and Metabolism;" Effect of Vitamin K Supplementation on Bone Loss in Elderly Wmen; S. Booth, et al.; April 2008
- Linus Pauling Institute; Vitamin K; Jane Higdon, Ph.D; May 2004
Member Comments