Carol Campi, MA, DC, BSN – Life Extension Wellness Specialist
We all know how important calcium and vitamin D are for our bones. And you probably know that vitamin K is necessary for blood to clot. But did you know that vitamin K has more than one form? The various forms are called vitamers. Vitamin K1 is needed to activate various clotting factors, while both K1 and K2 play a major role in our bone and arterial health.1 Vitamin K is vital for getting calcium into our bones and keeping it out of our arteries and soft tissue.2
What is Vitamin K and Where Do We Get It?
The vitamin K vitamers are fat-soluble molecules consisting of a common ring-like structure with side chains of varying lengths. There are several differences between K1, also known as phylloquinone, and K2, or menaquinone. The K1 side chain is monounsaturated and it is primarily found in the liver, while K2 is polyunsaturated and generally found in bone, cartilage and smooth muscle. K2 is further categorized by the number of carbon groups that make up its side chains, with two common forms being menaquinone 4 (MK-4) and menaquinone 7 (MK-7).
Vitamin K1 is plant-based and can be found in many leafy green vegetables, as well as algae and plant-based oils. Menaquinones are found mostly in fermented foods and in small amounts in animal-based foods. A very high amount of K2 is found in the traditional Japanese food nattō (fermented soybeans). Gut bacteria can convert K1 to K2 in animals, but it is still unclear how much this contributes to K2 formation in humans. How efficiently humans convert K1 to any form of K2 is also under investigation and is likely dependent on one’s genetics, gut health, diet and use of drugs such as Coumadin (warfarin). 3
What is the Function of Vitamin K2?
Vitamin K is required to activate specific vitamin K-dependent proteins. One of these is osteocalcin which, when activated, supports bone synthesis. This process occurs throughout life since bone is constantly being remodeled (i.e., resorbed and regenerated).2 The MK-4 form also has the unique role of regulating the expression of various genes, including those that promote bone growth.4 Together, these actions support bone quality and may impact bone density, lessening the risk of osteoporosis.
Another vitamin K-dependent protein is matrix GLA protein which, when it becomes activated by vitamin K2, inhibits the calcification of soft tissue such as our cartilage, tendons and the smooth muscle that surrounds our blood vessels.3 This is important because when calcium deposits in our arteries, it can lead to arterial stiffness, increased blood pressure and cardiovascular events likes heart attacks and strokes.
Benefits of Vitamin K2 for Bone Health
Numerous studies have shown positive benefits of vitamin K2 for bone health. Several observation studies in Japan, where nattō is a frequent staple, found that postmenopausal women consuming the most nattō had less bone loss over time.5 A three-year randomized controlled trial (RCT) using 180 mcg MK-7 in postmenopausal women found less decline in bone mineral density (BMD) in the lumbar spine and femoral neck; bone strength was also better-maintained and there was less loss of height in the thoracic spine.6 Several studies from Japan using very high doses of MK-4 (45 mg/day—that’s 45,000 mcg!) found a decreased incidence of bone fractures in postmenopausal women with osteoporosis.3 Given that the total recommended daily allowance (RDA) of vitamin K for adult women is only 90 mcg (and 120 mcg for men), this amount is much higher than any suggested nutritional dose coming from conventional sources. It is, however, a pharmacological dose that has been deemed safe, has been repeatedly found to support the bone health of osteoporotic, postmenopausal women, and is commonly prescribed in Japan per standard of care.7
Another study on healthy postmenopausal women given a much lower dose of 1500 mcg of MK-4 versus a placebo also found significant BMD improvement and an increase in activated osteocalcin.8 Thus, it appears that vitamin K2, in both the MK-4 and the MK-7 forms, helps to maintain BMD, support bone health and lessen the risk for fractures.
Benefits of K2 for Cardiovascular Health
The 2004 Rotterdam study on 2,400 healthy men and women over 55 looked at the association of dietary intake of K2 and aortic calcification and heart disease over a seven-year period. Ingesting at least 32 mcg of vitamin K2 was associated with a reduced risk for cardiovascular disease and an approximately 50% reduction in deaths related to arterial calcification.9 The 8-year European Prospective Investigation into Cancer and Nutrition (EPIC) study consisting of 16,000 participants between the ages of 49-70 found that for every 10 mcg increase in K2, mostly in the form of MK-7 and MK-9, there were 9% fewer coronary events.10
A double-blind RCT that gave postmenopausal women 180 mcg of MK-7 or a placebo found that after three years, the women given the MK-7 had less arterial stiffness and more flexible arteries.11 These effects could translate into healthier blood pressure and better delivery of nutrients and oxygen to the tissues and organs. The placebo group from this study was also found to have a higher amount of non-activated matrix GLA protein, which correlates with increased risk for calcium being deposited within the arterial walls.
Other Important Health Benefits from Vitamin K2
- K2 may reduce the risk of developing kidney stones by its role in activating a urinary GLA protein.12,13
- K2 has been found to support insulin sensitivity and glycemic control in those at risk of diabetes.14
- K2, specifically MK-4, is involved in turning on and off certain genes such as those involved in hormone production and bone growth.4
- K2 is associated with improved outcome in certain cancer cases.15
- K2 is found in high concentrations in the brain and may play a protective role in neurological health.15
The Relationship Between Calcium, Vitamin D and K2
Optimizing our levels of calcium, vitamin D and vitamin K2 are necessary for optimal health, especially as we age. Our bodies need 1,000-1,200 mg of calcium every day to maintain healthy bone turnover and D3 to support the absorption of that calcium from our intestinal tract into our circulation. But without sufficient vitamin K2 available to activate the vitamin K-dependent proteins such as matrix GLA and osteocalcin, much of that calcium is likely to get deposited inappropriately in our arteries, heart valves, joints and tendons, and not in our bones where it is needed.
A combination of dietary and supplemental sources can be used to get our daily calcium dosage. Ideally the amount of supplemental D3 should be determined by the amount required to maintain a blood level of 50-80 ng/mL—this will vary between people and may be anywhere from 2,000-8,000 IU (50-200 mcg) per day.16 The typical Western diet, heavy on processed foods, provides only very small amounts of K2, and even though K1 is quite abundant in green vegetables if consumed, much of it is not sufficiently converted to K2. Currently, there is no commercially available blood test for assessing K2 levels. Doses of MK-4 as high as 45 mg per day have been found to be safe and are routinely prescribed in Japan for osteoporotic women. However, based on the reviewed studies, a daily intake of 1,500 mcg of MK-4 and 180 mcg of MK-7 is likely more than sufficient.
Safety and Medication Interactions
The only safety concern for vitamin K revolves around its interaction with warfarin—a vitamin K antagonist. Warfarin and its family of anticoagulating drugs work by preventing K1 from activating various clotting proteins. Unfortunately, these drugs also interfere with the activation of matrix GLA and osteocalcin; common side effects of anticoagulants include an increased risk of aortic stenosis due to calcification and osteoporosis.17 Those individuals on warfarin should not alter their vitamin K1 or K2 intake without first consulting with their physicians. For the rest of us, unless you are fans of nattō or goose liver, it’s unlikely that you are getting adequate amounts of K2 from your diet. You may want to consider supplementing with the suggested amounts of MK-4 and MK-7 to help promote healthier bones, arteries and more.
About the author: Carol Campi, MA, DC, BSN has been a Wellness Specialist at Life Extension for the past 6 years and an enthusiast of health optimization and anti-aging science for most of her life. Her academic interests have ranged from research-based psychology to chiropractic to acute-care nursing. It was while working as an acute care nurse that she came to the realization that she could help more people by educating them on ways to prevent illness and optimize their health span. In her role as a Wellness Specialist at Life Extension she suggests and evaluates lab results, helps customers to optimize their diet with appropriate nutraceutical support and integrates conventional with holistic approaches to healthcare.
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