How Vitamin D and Vitamin K2 Help Osteoporosis
Recent evidence has shed more light on the efficacy of calcium supplementation in the treatment of osteoporosis. The consensus from researchers is that calcium supplements are a lot less important to proper bone mineralization than vitamins D and K. Specifically, vitamins D3 and K2 have been shown to significantly lower the risk of bone fractures by improving bone mineral density and bone strength. But how do these vitamin strengthen the bone? Should they be used in combination or singly? What benefits do they offer over high-dose calcium supplementation? Read on to find out.
by Brad Chase
Vitamins D and K are fat-soluble vitamins. While the body can synthesize vitamin D, vitamin K has to be obtained from the diet or nutritional supplements. However, the body synthesizes the form of vitamin K it needs from plant-derived vitamin K.
Vitamin D is also called the sunshine vitamin. This is because it is synthesized in the skin from a metabolite of cholesterol after sun exposure.
Although there are 5 different forms (vitamers) of vitamin D, the most important ones are vitamin D2 (cholecalciferol) and vitamin D3 (ergocalciferol).
Vitamin D3 is converted to calcidiol in the liver and then onward to calcitriol (the active form of vitamin D) in the kidneys.
Calcitriol functions as a hormone in the body. It improves bone health by regulating the levels of calcium and phosphate in the blood. Therefore, vitamin D deficiency reduces bone mineral density and increases the risk of osteomalacia, rickets and osteoporosis.
Vitamin D is also important to the cardiovascular system and the immune system.
There are also 5 vitamers of vitamin K. Two (vitamins K1 and K2) of these are naturally occurring while the others (vitamins K3, K4 and K5) are synthetic products.
Vitamin K1 is also known as phytomenadione or phylloquinone. It is produced by plants and required for photosynthesis.
Although phytomenadione is the plant form of vitamin K, it can also be utilized by humans. In fact, vitamin K1 is converted to vitamin K2. In humans, this conversion is done by the bacteria in the large intestines.
Vitamin K2 refers to a subfamily of related vitamers of vitamin K. They are known as menaquinones and the most common member of this class is MK-4 or menaquinone-4.
In humans, vitamin K is involved in blood clotting, bone health and metabolism in different tissues.
Therefore, vitamin K deficiency can increase the risk of severe bleeding and the deposition of calcium on cartilages, soft tissues and artery walls. This deficiency can also cause malformation of bones especially in infants and children.
Vitamin K2 deficiency is closely associated with poor bone health and the calcification of blood vessels.
Calcium has been relentlessly promoted to help improve bone health by restoring and/or preserving bone mineral density especially in the elderly. However, recent evidences suggest that calcium is only part of the requirement for healthy bones.
The importance of vitamin D to bone health is also now widely accepted because the link between low vitamin D levels and weak bones is established.
Vitamin D improves bone health by promoting the absorption of calcium into the blood and the retention of calcium in bones.
Studies show that combining vitamin D with calcium supplementation produces better results and significantly reduces the risks of bone fractures.
The form of vitamin D that provides the best benefits for bone health is vitamin D3.
Just as vitamin D helps calcium to improve bone health, vitamin K is also essential for the same reason.
By different mechanisms, vitamin K drives calcium into bones and improves bone mineral density.
Researchers believe that both vitamins should be combined with calcium to reduce the risks of bone diseases. In fact, taking large doses of calcium without vitamins K and D can be detrimental to cardiovascular health.
By simply raising blood calcium levels with calcium-only supplements, there is an increased risk of deposition of calcium of various organs of the body especially in the muscles, soft tissues, kidneys and blood vessels.
On the other hand, vitamins D and K drive calcium from the blood into the bones where it is needed.
How important is vitamin K to bone health? Studies show that vitamin K is even more important than vitamin D.
In one study published in the International Journal of Gynecology and Obstetrics in 1997, researchers found that high intakes of vitamin D combined with low intakes of vitamin K reduced bone mineral density and increased the risk of hip fracture.
While studies have shown that both vitamins K1 and K2 can strengthen the bones by complementing the actions of calcium and vitamin D, vitamin K2 is the more important vitamer.
Of the various forms of vitamin K2, MK-4 and MK-7 are the most effective forms for improving bone health.
A 2006 review published in the Annals of Internal Medicine examined the results of past studies done to investigate the possible link between vitamin K and bone fractures.
The authors reviewed 13 studies in which vitamin K and MK-4 were administered to adult patients for at least 6 months. These long-term studies represent the best test of the effect of vitamin K on the risk of bone fractures.
The authors concluded that vitamin K reduced bone loss and that it can help reduce the risk of hip fracture.
A 1993 study took another approach to the link between vitamin K and bone loss. In this study published in the Journal of Bone and Mineral Research, the researchers measured the serum levels of vitamin K1, MK-7 and MK-8 in a group of adults
The results of the study showed that those with bone fractures had markedly lower levels of all 3 forms of vitamin K.
A 2000 study published in the same journal built on past studies to determine whether vitamin K2 supplementation can lower the risk of new fractures in people with osteoporosis. For this 24-month study, the researchers gave each of the 241 osteoarthritic patients either no treatment or 45 mg/day oral vitamin K2.
By measuring the participants’ lumbar bone mineral density and serum vitamin K levels, the researchers determined that vitamin K2 supplementation can prevent the occurrence of new fractures in osteoarthritic patients even though it did not affect lumbar bone mineral density.
Studies show that the effect of vitamin K supplementation on bone mineral density varies between men and women. One example of such studies was a 2003 study published in the American Journal of Clinical Nutrition.
For this study the researchers correlated dietary vitamin K intake with bone mineral density in 1,112 men and 1,479 women aged between 29 and 86 years.
The results of the study showed that low dietary intake of vitamin K was strongly linked with low bone density mineral in women and also an increased risk of bone fractures. In contrast, the study did not find such link between vitamin K intake and bone mineral density in men.
A review of studies and clinical experience in the use of vitamin K for improving bone health was published in the journal, Nutrition, in 2001.
The authors confirmed that vitamins D and K produced the best results for improving bone health.
They also highlighted the use of high doses of vitamin K2 in studies investigating the beneficial effects of the vitamin to bone health.
However, the reviewers pointed to new evidences suggesting that vitamin K1 at lower doses can also improve bone health as long as it is administered along with vitamin D.
The authors stated that health regulatory bodies now recognize the importance of vitamin K to bone health. Therefore, the dietary reference intakes of vitamin K has been raised by 50% (90 micrograms per day for women and 120 micrograms per day for men).
A 3-year intervention study investigated the benefits of combining calcium and vitamin for preventing bone fractures caused by osteoporosis in the elderly.
This 2004 study published in the Journal of Bone and Mineral Research involved 9,605 community-dwelling residents of a region known to suffer from vitamin D deficiency.
Approximately half of this population was placed on 1000 mg of calcium as calcium carbonate supplement and 400 IU vitamin D3 while the other half received no supplements. The researchers recorded a 16% reduction in the incidence of fractures among the residents who received calcium and vitamin D compared to those who did not.
The researchers, therefore, concluded that the combination of calcium and vitamin D is recommended for preventing bone fracture among vitamin D deficient osteoporosis patients.
A 2001 Japanese study investigated the benefits of combining vitamin D3 and vitamin K2 over supplementing with only one of the vitamins in the prevention of bone loss.
The researchers divided some female rats, with their ovaries removed, into 4 groups. Over the course of 8 weeks, one group got placebo; another group received 30 mg/kg of vitamin K2; the third group was given 0.3 microgram/kg of vitamin D3; and the last group took a combination of both vitamins.
By comparing bone densities in different regions of the body, the researchers found that the combination of vitamins D3 and K2 produced superior results to only vitamin D3 or vitamin K2.
But how does vitamin D3 and K2 interact to improve bone health? A 2001 study published in the journal, Osteoporosis International, provided a good insight.
The authors first recognized that past studies had established that vitamin K2 (MK-4) stimulated vitamin D3 to increase bone mineralization by inducing the carboxylation of osteocalcin and then accumulating the protein in osteoblasts.
In this study, they demonstrated that vitamin D3 also stimulated vitamin K2 to act as cofactor in the carboxylation of osteocalcin in bone cells.
Therefore, vitamins D3 and K2 help each other along and produce a synergistic effect on bone mineralization.
To investigate whether the combination of vitamins D3 and K2 can indeed increase calcium uptake in bones, a group of Japanese researchers divided 92 postmenopausal women with osteoporosis into 4 groups.
One group was given 0.75 micrograms per day of vitamin D3; another group received 45 mg/day of vitamin K2; a third group was given the combination of the 2 vitamins while the last group received 2 g/day of calcium lactate.
The results of the study was published in the Journal of Orthopaedic Science in 2000.
The researchers found that bone mineral density was significantly higher in the groups given vitamin D3 alone and vitamin K2 alone compared to the group that received only calcium.
In addition, they found that the group that got the combination of vitamin D3 and vitamin K2 had the highest bone mineral density.
Therefore, they recommended that postmenopausal women with osteoporosis should receive vitamin D3 and vitamin K2 supplements rather than calcium supplement alone. They also recommended the combination of both vitamins over supplementation with only one of either vitamins.
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