**1. Introduction**

Vitamin K2 (menaquinone‐4, MK‐4, or menatetrenone) is a very important vitamin K species serving special functions in several extrahepatic organs, like bone tissue, heart, blood vessels, kidneys, brain, and cartilage. MK‐4 is a member of a sub‐family with eliciting the same cellular reactions, but with different effects. MK‐4 is deemed necessary for γ‐carboxylation of proteins, and activation of the vitamin K‐dependent proteins, i.e., Osteocalcin (bone‐Gla‐protein), matrix‐ Gla proteins (MGPs), Periostin, as well as protein S. Without these activated proteins, the body

© 2017 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2017 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

is not able to regulate the process of calcium uptake and bone mineralization. To date, we know of 19 different vitamin K‐dependent proteins. The process also ensures the access of energy for a plethora of cellular reactions. The most common of the K vitamins is phylloquinine‐1 (K1). K1 is found in leafy green vegetables, olive oil, and soybean oil, while MK‐4 is found in small amounts in egg yolks, butter, and hard cheese. Fermented soybeans, known as natto, a special Japanese food, contain another subfamily member menaquinone‐7 (MK‐7). It is the richest dietary source of menaquinones (yielding about 1100 μg/100 g). In Western diets, MK‐7 in fermented cheeses amounts to only 62 μg/100 g, approximately. Very small amounts of MK‐4 are produced by intestinal bacteria. The adequate intake (AI) for vitamin K1 from 2001 in the United States and Canada was recommended to be 90 μg/day for women, 120 μg/day for men. These values are based on the need for hepatic vitamin K1 to ensure sufficient clotting factor synthesis. To date, we know that the early AI is not enough to meet the request for a complete carboxylation of all the extrahepatic vitamin K‐dependent proteins. When MK‐4 ingestion is insufficient, the serum concentration of uncarboxylated MGP (ucMGP) or uncarboxylated Osteocalcin (ucOC) is increased. This serves as the major sign of a deficient intake of K1 or a deficient hepatic transformation of vitamin K1 to MK‐4. High serum concentrations of MK‐1 and MK‐4 reflect only the recent intake of vitamin K, not the accumulation or steady state levels of a "chronic" intake. The bioavailability of K1 and MK‐4 is very short, i.e., about 1.5–3 h in contrast to 72 h for MK‐7. To date, K1, MK‐4, and MK‐7 are available as dietary supplements [1, 2].

like the Netherlands, as shown by the group of Knaben et al. [9] and Finland, as shown by Luukinen et al. [10], clearly demonstrated that this association (ucOC versus fracture risk) point to the fact that vitamin K status is a predictor of bone health (fracture‐free percentage of a population group). The correlation between low intake of vitamin K and increased fracture rate was also revealed by prospective analysis within the Nurses' Health Study cohort 1984. Here, the diet was assessed in 72,327 women, aged 38–63 years, with a food‐frequency baseline‐ questionnaire. During the subsequent 10 years of follow‐up, 270 hip fractures resulting from low or moderate trauma were reported. Results: women in quintiles 2–5 of vitamin K intake had a significantly lower age‐adjusted relative risk (RR: 0.70; 95% CI: 0.53, 0.93) of hip fracture

Vitamin K2 and Bone Health http://dx.doi.org/10.5772/64876 103

In Japan, a high dose of menaquinone‐4 (MK‐4) of 45 mg/day (15 mg × 3/day) was used as therapeutic treatment for osteoporosis. The principle cause‐effect of vitamin K2 on osteopo‐ rosis is mainly the prevention of bone fractures due to its improvement of bone quality, and not the ensuing increasing bone mineral density. Due to variable contents of vitamin K in the diet, the Japanese Society of Osteoporosis included in 1995 vitamin K2 as Menatetrenone (MK‐

Osteoporosis, in its primary form, is characterized by bone loss, and the age of females upon onset or development of menopause, however, the disease also affects a smaller cohort of men. Genetics is the single most important cause for both sexes, however, changes of lifestyle, exercise levels, smoking habits, and low body weight, are important contributors, which may trigger the onset of the disease. Secondary forms of osteoporosis‐related chronic diseases are rheumatoid arthritis, chronic lung disease, and anorexia. In addition, it is well known that the use of cortisone or prednisolone can reduce bone mineral density (BMD). Standard examina‐ tion of bone mineral density (BMD) is the dual energy X‐ray absorptiometry (DEXA). BMD values is not the same for all women and men but different due to race. In the last decade, research have combined DEXA scan with more specific geometric hip and vertebra measure‐ ments as femoral neck width (FNW) and hip‐axis length (HAL) and vertebral fracture (VF)

However, it may be asserted to a certain extent, that proper bone 3D‐architecture may "make up" for a marginal reduction in BMD‐values in terms of predictive value of the BMD‐levels

The incidence of osteoporosis is lower in Japanese women, even though they are subjected to the same period with menopause as other women. However, in some regions, like in Tokyo, the intake of vitamin K as MK‐7 in the special fermented food of natto, soybeans together with other treatments result in higher BMD‐values and lower fracture rates than age‐matched

Of other health outcome studies featuring patients with an without osteoporosis, a few warrant special attention: observational studies of subjects displaying a low long‐term vitamin K intake revealed a higher incidence of osteoarthritis in the hand and knee [13], dementia [14, 15]. From population‐based studies of atherosclerosis, Jie et al. revealed that, in atherosclerotic women, vitamin K status is associated with lower bone mass. All these findings support our hypothesis

4), together with vitamin D, in the first line treatment of osteoporosis [12].

than women in the lowest quintile [11].

assessment (VFA).

woman in the United States and Europe [3].

*per se*.

Osteoporosis is, on a worldwide basis, the reason for many emerging, spontaneous fractures. On a global basis, osteoporosis causes more than 88.9 million fractures annually. The condition is estimated to affect 200 million women worldwide, i.e., approximately one‐tenth of women aged 60, one‐fifth of women aged 70, two‐fifths of women aged 80, and two‐thirds of women aged 90 years. Worldwide, one in three women over the age of 50, will experience osteoporotic fractures, as will one in five of men aged over 50 [3]. From Europe, the number of new fractures in 2010 was estimated at 3.5 million, comprising approximately 620,000 hip fractures, 520,000 vertebral fractures, 560,000 forearm fractures, and 1,800,000 of other fractures (types or sites). For women in the EU: approximately 50% of fractures related deaths, were due to hip fractures, 28% to clinical vertebral fractures, and 22% to other types of fractures. In men, the correspond‐ ing figures were 47, 39, and 14%, respectively [3]. From the USA Preventive Services Task Force (USPSTF) for 2013, it is therefore concluded that the current evidence is insufficient to assess the balance of the benefits and harm of combined vitamin D and calcium supplementation for the primary prevention of fractures In the treatment of pre‐ and postmenopausal women or in men, these indicate that new treatments of osteoporosis are wanted [3, 4].

In 1984, Hart et al. [5] revealed that the serum concentrations of vitamin K1 were very low among patients with hip fractures, and hypothesized that poor vitamin K status is associated with increased rates of osteoporotic fractures. The period of 1991–1993 was regarded as the beginning of the era of vitamin K examinations, since patients‐based studies by Hodges et al. confirmed that low serum concentrations of vitamin K1 and K2 were associated with increased risk of spine and hip fracture. The same phenomena were also shown by Szulc et al. in a French study, yielding a positive association between ucOC and fracture risk [6–8]. Other countries, like the Netherlands, as shown by the group of Knaben et al. [9] and Finland, as shown by Luukinen et al. [10], clearly demonstrated that this association (ucOC versus fracture risk) point to the fact that vitamin K status is a predictor of bone health (fracture‐free percentage of a population group). The correlation between low intake of vitamin K and increased fracture rate was also revealed by prospective analysis within the Nurses' Health Study cohort 1984. Here, the diet was assessed in 72,327 women, aged 38–63 years, with a food‐frequency baseline‐ questionnaire. During the subsequent 10 years of follow‐up, 270 hip fractures resulting from low or moderate trauma were reported. Results: women in quintiles 2–5 of vitamin K intake had a significantly lower age‐adjusted relative risk (RR: 0.70; 95% CI: 0.53, 0.93) of hip fracture than women in the lowest quintile [11].

is not able to regulate the process of calcium uptake and bone mineralization. To date, we know of 19 different vitamin K‐dependent proteins. The process also ensures the access of energy for a plethora of cellular reactions. The most common of the K vitamins is phylloquinine‐1 (K1). K1 is found in leafy green vegetables, olive oil, and soybean oil, while MK‐4 is found in small amounts in egg yolks, butter, and hard cheese. Fermented soybeans, known as natto, a special Japanese food, contain another subfamily member menaquinone‐7 (MK‐7). It is the richest dietary source of menaquinones (yielding about 1100 μg/100 g). In Western diets, MK‐7 in fermented cheeses amounts to only 62 μg/100 g, approximately. Very small amounts of MK‐4 are produced by intestinal bacteria. The adequate intake (AI) for vitamin K1 from 2001 in the United States and Canada was recommended to be 90 μg/day for women, 120 μg/day for men. These values are based on the need for hepatic vitamin K1 to ensure sufficient clotting factor synthesis. To date, we know that the early AI is not enough to meet the request for a complete carboxylation of all the extrahepatic vitamin K‐dependent proteins. When MK‐4 ingestion is insufficient, the serum concentration of uncarboxylated MGP (ucMGP) or uncarboxylated Osteocalcin (ucOC) is increased. This serves as the major sign of a deficient intake of K1 or a deficient hepatic transformation of vitamin K1 to MK‐4. High serum concentrations of MK‐1 and MK‐4 reflect only the recent intake of vitamin K, not the accumulation or steady state levels of a "chronic" intake. The bioavailability of K1 and MK‐4 is very short, i.e., about 1.5–3 h in contrast to 72 h for MK‐7. To date, K1, MK‐4, and MK‐7 are available as dietary supplements [1,

Osteoporosis is, on a worldwide basis, the reason for many emerging, spontaneous fractures. On a global basis, osteoporosis causes more than 88.9 million fractures annually. The condition is estimated to affect 200 million women worldwide, i.e., approximately one‐tenth of women aged 60, one‐fifth of women aged 70, two‐fifths of women aged 80, and two‐thirds of women aged 90 years. Worldwide, one in three women over the age of 50, will experience osteoporotic fractures, as will one in five of men aged over 50 [3]. From Europe, the number of new fractures in 2010 was estimated at 3.5 million, comprising approximately 620,000 hip fractures, 520,000 vertebral fractures, 560,000 forearm fractures, and 1,800,000 of other fractures (types or sites). For women in the EU: approximately 50% of fractures related deaths, were due to hip fractures, 28% to clinical vertebral fractures, and 22% to other types of fractures. In men, the correspond‐ ing figures were 47, 39, and 14%, respectively [3]. From the USA Preventive Services Task Force (USPSTF) for 2013, it is therefore concluded that the current evidence is insufficient to assess the balance of the benefits and harm of combined vitamin D and calcium supplementation for the primary prevention of fractures In the treatment of pre‐ and postmenopausal women or

in men, these indicate that new treatments of osteoporosis are wanted [3, 4].

In 1984, Hart et al. [5] revealed that the serum concentrations of vitamin K1 were very low among patients with hip fractures, and hypothesized that poor vitamin K status is associated with increased rates of osteoporotic fractures. The period of 1991–1993 was regarded as the beginning of the era of vitamin K examinations, since patients‐based studies by Hodges et al. confirmed that low serum concentrations of vitamin K1 and K2 were associated with increased risk of spine and hip fracture. The same phenomena were also shown by Szulc et al. in a French study, yielding a positive association between ucOC and fracture risk [6–8]. Other countries,

2].

102 Vitamin K2 - Vital for Health and Wellbeing

In Japan, a high dose of menaquinone‐4 (MK‐4) of 45 mg/day (15 mg × 3/day) was used as therapeutic treatment for osteoporosis. The principle cause‐effect of vitamin K2 on osteopo‐ rosis is mainly the prevention of bone fractures due to its improvement of bone quality, and not the ensuing increasing bone mineral density. Due to variable contents of vitamin K in the diet, the Japanese Society of Osteoporosis included in 1995 vitamin K2 as Menatetrenone (MK‐ 4), together with vitamin D, in the first line treatment of osteoporosis [12].

Osteoporosis, in its primary form, is characterized by bone loss, and the age of females upon onset or development of menopause, however, the disease also affects a smaller cohort of men. Genetics is the single most important cause for both sexes, however, changes of lifestyle, exercise levels, smoking habits, and low body weight, are important contributors, which may trigger the onset of the disease. Secondary forms of osteoporosis‐related chronic diseases are rheumatoid arthritis, chronic lung disease, and anorexia. In addition, it is well known that the use of cortisone or prednisolone can reduce bone mineral density (BMD). Standard examina‐ tion of bone mineral density (BMD) is the dual energy X‐ray absorptiometry (DEXA). BMD values is not the same for all women and men but different due to race. In the last decade, research have combined DEXA scan with more specific geometric hip and vertebra measure‐ ments as femoral neck width (FNW) and hip‐axis length (HAL) and vertebral fracture (VF) assessment (VFA).

However, it may be asserted to a certain extent, that proper bone 3D‐architecture may "make up" for a marginal reduction in BMD‐values in terms of predictive value of the BMD‐levels *per se*.

The incidence of osteoporosis is lower in Japanese women, even though they are subjected to the same period with menopause as other women. However, in some regions, like in Tokyo, the intake of vitamin K as MK‐7 in the special fermented food of natto, soybeans together with other treatments result in higher BMD‐values and lower fracture rates than age‐matched woman in the United States and Europe [3].

Of other health outcome studies featuring patients with an without osteoporosis, a few warrant special attention: observational studies of subjects displaying a low long‐term vitamin K intake revealed a higher incidence of osteoarthritis in the hand and knee [13], dementia [14, 15]. From population‐based studies of atherosclerosis, Jie et al. revealed that, in atherosclerotic women, vitamin K status is associated with lower bone mass. All these findings support our hypothesis that vitamin K status affects the mineralization processes in both bone and atherosclerotic plaques in a healthy manner [16]. And, from the population‐based Rotterdam Study, the relation between low vitamin K status and development of coronary artery disease [17] is indisputable.

that MK‐7 reinforces the synthesis of various bone‐specific proteins, mediated through the pathways of calcium‐dependent protein kinase C signaling, as well as cyclic AMP‐dependent signaling. MK‐7 also antagonizes the "receptor activator of NF‐κB (RANK) ligand (RANKL)" induced NF‐κB activation on osteoclast precursors. This concept now makes up the basis for the search of novel antiosteoporotic medication regimens, mimicking the plethora of effects

Vitamin K2 and Bone Health http://dx.doi.org/10.5772/64876 105

In relation to the loss of bone associated by deficient intake of vitamin K1, many observational studies have been conducted. However, few randomized studies have been able to reveal a significant positive rebuilding of bone mass and increased BMD. This chapter deals only with

Schaafsma et al. from the Netherlands showed in a 1‐year long randomized study from 2000 [32] (featuring four groups with 400 IU vitamin D3; vitamin K1 supplementation 80 μg daily, vitamin K1 and D3, and placebo of Dutch postmenopausal women (with a patient total, *n* = 141) with either normal or low bone mineral densities (BMD). It was shown that women with low BMD had a lower %cOC at baseline than the women with normal BMD. However, this difference disappeared after 1 year of supplementation with vitamin K1 [(mean ± S.D.) 68 ± 11% (95% CI = 64.5 ± 71.2%) versus 72 ± 6% (95% CI = 70.1 ± 72.9%)], respectively. On the other hand, 1 year of supplementation with vitamin D3 showed maximum increases in 25(OH)D of 33 ± 29% (95% CI = 24.8 ± 41.8%) and 68 ± 58% (95% CI = 50.1 ± 84.6%) in women with normal and

In the Bram et al. study from 2003, three groups were examined; group K1D: the effect of vitamin K1 (1 mg/day) and vitamin D (8 μg/day including standard mineral supplementation), group D (vitamin D and minerals) and group 3, placebo on bone loss retardation in a random‐ ized, double‐blind, placebo‐controlled 3‐year intervention study. Of 181 healthy postmeno‐ pausal women between 50 and 60 years of age, 155 completed the observation period. The main outcomes of the study were significant changes in BMD‐values of the femoral neck and lumbar spine after 3 years. The group receiving the supplement with additional vitamin K1 showed a decline in the bone loss from the femoral neck. The difference in femoral neck bone mass between the K1D group and the placebo group was 1.7% (95% CI: 0.35–3.44). The difference between the K1D group and the D group was 1.3% (95% CI: 0.10–3.41). No significant differences were observed among the three groups with respect to changes in BMD at the site of the lumbar spine. It was therefore concluded that the minerals and vitamin D, coadminis‐ tered with the vitamin K1 supplement, substantially contributed to a significant reduction in

In a systematic review and meta‐analysis of 700 patients, Cockayne et al. showed in 2006 that the MK‐4 intake in Japan yielded a powerful reduction in the incident of fractures. However, the authors would not recommend vitamin K supplementation until a new randomized clinical

**3. Clinical‐related publications featuring K1 supplementation**

randomized clinical trials with a duration exceeding 1 year.

low BMD, respectively. No effect was observed on BMD [32].

postmenopausal bone loss at the site of the femoral neck [33].

trial confirmed the results [34].

induced by MK‐7 [31].

The importance of vitamin D for bone health has been known since it was used in the treatment of rachitis in the 1930s. Vitamin D and calcium supplements have been recommended as a pillar in the treatment of osteoporosis over the last three decades. Vitamin D and calcium supplementation increases spinal BMD in healthy, postmenopausal women [18, 19], and vitamin D is crucial in the process of mobilizing the Ca2+ ions into the bone tissue [20]. Interestingly, vitamin D and calcium alone are not able to rebuild bone tissue and infrastructure that are being lost. The synergistic effect of vitamin D and retinoic acid on osteoblast produc‐ tion of osteocalcin was shown in 1993 [21], where Hara et al. demonstrated that MK‐4 was able to partly inhibit the bone resorption induced by inflammation, vitamin D loss and ensuing PTH induction, as seen in the calvariae and incubation medium in his mode *ex vivo* model system. This observation served later as the basis for the introduction and acknowledgement of menatetrenone (MK‐4) supplementation in the clinic [22]. And finally, in 1995, Hara et al. [23] also showed that the inhibition of bone resorption was related to vitamin K2's long side chain.
