by Barbara Porwolik and Katarzyna Maresk, Ph.D.
Dietary calcium is crucial for bone metabolism and bone health, but is calcium alone enough? And are you getting the right kind? Researchers now recognize other essential nutrients are necessary for its use in the body, but there is a very real risk the calcium you take may not be used to build strong bones. Instead, it could end up in your arteries and soft tissues, a development referred to as the “Calcium Paradox.”
Doing nothing is not an option, as neglecting your bones can lead to health consequences down the road, namely osteoporosis, a disease characterized by low bone mass and structural deterioration of bone tissue. It leads to bone fragility and an increased susceptibility to fractures. The hip, spine, and wrist are the main targets, though any bone is at risk. The scary part is you cannot feel your bones getting weaker; many don’t know they have osteoporosis until they break a bone.
According to the National Osteoporosis Foundation, the disease is a major public health threat for an estimated 44 million Americans or 55 percent of the people 50 years and older. In the U.S. today, 10 million are estimated to already have the disease and almost 34 million more are estimated to have low bone mass, placing them at increased risk for osteoporosis.
Aside from lifestyle and dietary adjustments—more weightbearing and muscle-strengthening exercises, less (or no) drinking alcohol or smoking—getting the right amounts of calcium is crucial, including vitamins such as D and now newly recognized vitamin K2. This needs to be done as early as possible. Bone building peaks in the late twenties, so the more you have in your younger years, the more you have to lose.
Recent studies have shown that vitamin K is essential to putting calcium in bone tissue. Populations that consume larger amounts of vitamin K have fewer fractures, and stronger, healthier bones. But as the “Calcium Paradox” reveals getting enough calcium is only half the battle. It needs to stay away from the heart.
Vitamin K has found the loophole in the paradox
Calcium can accumulate in your arteries, leading to atherosclerosis, or hardening of the arteries, and setting us up for possibly a heart attack or stroke. Previously believed to be an unavoidable result of aging, the medical community now recognizes that arterial calcification is actively regulated by a vitamin K-dependent protein called Matrix Gla Protein (MGP). Vitamin K is required to activate MGP. Without adequate amounts of vitamin K, MGP can’t function to keep calcium away from the heart’s arteries and soft tissues. It is now known that a type of vitamin K, vitamin K2, is what’s required by the body to help inhibit arterial calcification. In other words, with vitamin K2, you can have your cake and eat it, too.
As big a problem as osteoporosis is, it pales in comparison to cardiovascular disease (CVD), caused most often by atherosclerosis. In 2005, the American Heart Association estimated that over 80 million people in the United States have one or more forms of CVD.
Special K vs. Not-So Special K
Vitamin K actually refers to a group of fat-soluble vitamins, all of which are similar in structure. They share a “quinone” ring, but vitamin K2 has more carbon bonds (or “side chains”) off of the main ring, making it more effective in performing essential functions within the body.
So, the longer the chain of menaquinones in vitamin K2, the more useful it is. That means the vitamin will spend more time in the blood (so it’s available for all tissues) and be better absorbed, meaning the body will need smaller doses of vitamin K to fulfill its needs.
Presently there are three forms of K vitamins available in dietary supplements: synthetic vitamin K1, synthetic vitamin K2 as menaquinone-4 (MK-4), and natural vitamin K2 as menaquinone-7 (MK-7). The last is the most bioavailable, bioactive, and longest lasting form of vitamin K. Scientific research and clinical trials have demonstrated K2 is much more effective than K1 in preventing bone loss, and only K2 has been linked to the prevention of calcification. From the two available forms of vitamin K2, only MK-7 is effective at doses that do not exceed the present recommendations for daily vitamin K intake. The presently used Recommended Daily Allowance (RDA) for K vitamins is 90 mcg for women, and 120 mcg for men.
Though vitamin K1 is available in leafy, green vegetables, it’s very poorly absorbed. Only about 10 percent of K1 obtained from food reaches the circulatory system, but it’s quickly excreted and may not reach the heart or the bones. Most of it gets used by the liver for coagulation, one of the body’s most vital processes. For many years it was thought vitamin K function was exclusively related to blood coagulation, but beginning in the mid-1980s, the emphasis shifted toward bone health. Now, a clear picture of how vitamin K supports bone health has developed.
Vitamin K and Building Bone
The skeleton is rebuilt every seven years in a process called remodeling. This process is regulated by osteoblasts, cells that build up the skeleton, and osteoclasts, cells that break down the skeleton. As long as the bone-building activity of osteoblasts (absorption) exceeds the destructive action of osteoclasts (resorption), the process of maintaining healthy bone is kept under control.
Osteoblasts produce a vitamin K-dependent protein called osteocalcin, which helps pull calcium from the blood and bind it in the bone matrix as mineral content. Its function is to make the skeleton resistant and less susceptible to fracture. Because osteocalcin needs vitamin K to function, long-term K-deficiency will lead to significantly reduced density and quality of bone. The breakdown-happy osteoclasts will remove more bone tissue than the bone-forming osteoblasts can form, resulting in a slow but sure loss of bone tissue. The bones then become thin and fragile and easily susceptible to fracture.
Several studies have shown a correlation between vitamin K and bone health. A groundbreaking study in Japan showing the correlation between eating natto—a traditional Japanese dish ripe with natural vitamin K—and osteoporosis suggested that higher MK-7 levels from natto consumption can contribute to bone health. Increased intake of MK-7 from natto resulted in better levels of activated osteocalcin and a reduced risk fracture. These results were confirmed in a 2006 study that concluded consuming natto may help prevent the development of osteoporosis. This three-year study conducted on 944 women (aged 20–79) linked intake of MK-7 to the inhibition of bone mineral density loss.
This year, a study published in the European Journal of Epidemiology showed that while calcium, magnesium, zinc, and vitamin D were slightly indicated as important to bone health, consumption of natural vitamin K2 (again, from natto) was strongly associated with lowering the risk of hip fracture, indicating an important role of MK-7 in the prevention of bone disorders.
Vitamin K has also been shown to build bone during the crucial childhood years. Another study examining kids over a two-year period in 2008, this one appearing in British Journal of Nutrition, concluded that higher levels of vitamin K were found to be strongly associated with better mass, geometry, and mineral content of bone. Findings from previous studies have also indicated that additional K vitamins intake might improve bone geometry and positively influence the gain in bone mass. That contributing effect has been recently reported by O’Connor, et al, who, while conducting a study in a cohort of 223 healthy girls (11–12 years), found better K vitamins status related to higher bone mineral density. Thus, consuming more K vitamins leads to stronger, healthier bones.
The Heart of the Matter
Earlier in this article, we referenced the Calcium Paradox, which vitamin K bypassed by providing calcium to the body while helping to keep it away from the heart, staving off atherosclerosis. Two major studies out of the Netherlands showing added benefits of vitamin K2 may lead to a “Dutch corollary.”
Findings of The Rotterdam Study (2004) proved that high dietary intake of vitamin K2—but not K1—has a strong protective effect on heart health. Research conducted on a group of 4,807 elderly men and women indicated that eating large quantities of natural vitamin K2 (at least 32 mcg per day) reduced the risk of both arterial calcification and cardiovascular mortality by as much as 50 percent—with absolutely no undesirable side effects.
In the second study, published this year, Dutch researchers investigated the association of intake of vitamin K1 and vitamin K2 (including its subtypes MK4–MK10) with coronary calcification in a cross-sectional study among 564 postmenopausal women. The study found that “high dietary menaquinone [vitamin K2] intake, but probably not phylloquinone [vitamin K1], is associated with reduced coronary calcification. Adequate menaquinone intakes could therefore be important to prevent cardiovascular disease.”
It has been shown that in cases of CVD, people with diseased aortas showed lack of both K vitamins. However, research has found a high level of vitamin K2 in healthy aortas, but a barely detectable amount of vitamin K1. It suggests the vessel wall has a preference for vitamin K2 uptake, and K2 is the major K vitamin involved in the proper function of the cardiovascular system.
Despite its bevy of healthful benefits, the majority of adults and children are vitamin K deficient. The dietary intake of vitamin K in children has actually declined gradually in recent years. Meat and eggs have small amounts of natural vitamin K2, and the best source, natto, a traditional Japanese dish made of fermented soybeans, has an intense odor and a taste described as “controversial.”
Supplementation is actually the best bet. One ingredient that is now available as an extract of natto providing natural vitamin K2 as the longer chain menaquinone-7 (MK-7) form of vitamin K called MenaQ7™ Natural Vitamin K2. Numerous studies have shown the benefits of MenaQ7. According to a 2007 study published in Blood, there was “a major difference” between MenaQ7 and vitamin K1, namely “the very long half-life time of MK-7, resulting in much more stable serum levels, and accumulation of MK-7 to higher levels (7- to 8-fold) during prolonged intake.” Again, MK-7 is the most bioactive, bioavailable and longest lasting form of vitamin K.
A study pending publication with MenaQ7 in kids showed scientifically proven changes in osteocalcin, strongly suggesting that a 45 mg of MenaQ7 providing 45 mcg of Mk-7 reaches the bone and is able to affect the metabolic activity of osteoblasts—the bone-forming cells. This is further proof that natural vitamin K2 may provide the answer to the Calcium Paradox, helping to keep calcium in the bones where it is needed, and out of the arteries where it is not wanted. Additional information is available at www. vitamink2.org.