Vitamin K1 and K2 for Strong Bones and Healthy Arteries

Rear view of man flexing muscles against brick wall
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Long known for its vital role in the process of clotting blood (the K is for “koagulation”), Vitamin K should also be recognized for its contribution to bone fracture prevention. Vitamin K allows the body to utilize the calcium needed for bone and tooth formation.

Keeping your bones strong is a crucial part of staying healthy with age. According to the National Osteoporosis Foundation, 50 percent of women and 25 percent of men over 50 will have an osteoporosis-related fracture during their lifetime, and those fractures can be devastating, resulting in pain, disability, loss of independence, and a greater mortality risk.

Forms of Vitamin K

There are two natural forms of Vitamin K. Vitamin K1 is found in plentiful amounts in leafy greens, green vegetables like kale, collard greens, spinach, and mustard greens. Vitamin K2 is lesser known and is not as easily acquired in a plant-rich diet. The human body can synthesize some K2 from K1, and intestinal bacteria can produce some K2, but only in very small amounts. If you follow a nutrient-dense, plant-rich diet, with smaller amounts of animal products and more vegetables, beans, nuts and seeds, supplementing with K2 is likely wise.

Health Benefits of Vitamin K

In Japan, where natto, a fermented soybean food rich in Vitamin K2 is a typical part of the diet, there has been a low incidence of hip fracture. Studies have attributed the low hip fracture incidence there in part to natto. Following this observation, several studies found supplementation with Vitamin K2 to be particularly effective at improving bone health. A review of randomized controlled trials found that Vitamin K2 reduced bone loss and greatly reduced the risk of fractures: vertebral fracture by 60 percent, hip fracture by 77 percent, and all non-vertebral fractures by 81 percent.

In women who already have osteoporosis, Vitamin K2 supplementation has been shown to reduce the risk of fracture, reduce bone loss, and increase bone mineral density. In postmenopausal women taking Vitamin K2 supplements daily for three years, decreases in bone loss and bone mineral density, and increased bone strength were found in those taking the supplement versus those given a placebo.

In addition to its growing importance to bone health, there is some evidence that K2 has additional benefits (separate from those of K1) for the the cardiovascular system. Higher vitamin K2 intake has been linked with a lower likelihood of coronary calcification, helping to keep the artery wall elastic and prevent stiffening. Coronary artery calcification is a predictor of cardiovascular events, as is arterial stiffness.

In 2004, the Rotterdam Study revealed that increased dietary intake specifically of Vitamin K2 significantly reduced the risk of coronary heart disease by 50 percent as compared to a low dietary Vitamin K2 intake. Similar results were found in 2009, and a systematic review of several studies in 2010 also found a higher intake of Vitamin K2 was associated with a lower risk. No such association was found, however, for Vitamin K1.

Vitamin K2’s ability to protect the cardiovascular system against calcification could be due to differences in absorption or biological activity between the forms of Vitamin K. Future studies are needed to better understand Vitamin K2’s abilities and to parse out whether there are other benefits exclusive to either K1 or K2. There is some evidence that Vitamin K is involved in insulin metabolism, and higher intake of Vitamins K1 and K2 are associated with a lower risk of type 2 diabetes. For now, supplementing with Vitamin K2 (in addition to eating your greens) is likely to offer benefits.

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