Lurking among our dietary leafy greens is a key fat-soluble vitamin that allows humans to form bones and clot blood—vitamin K. Vitamin K's role in bone health has been the subject of many headlines lately, especially after research shows few get enough of it. Although one cup of spinach contains two times the current RDA (about 120mcg), recent research shows vitamin K may not be as abundant as once thought and, therefore, many may be experiencing deficiencies. A survey by the USDA Human Nutrition Research Center on Aging at Tufts University found that people between the ages of 18 and 44 do not ingest enough vitamin K.

Vitamin K helps to regulate calcium, keeping it in the bones and out of the arteries; this action also helps stop osteoporosis and heart attacks. The vitamin does this by mediating a type of protein that controls calcium, gamma-carboxyglutamic acid. Vitamin K also is a mediator of gamma-carboxylation, which means it enhances the activity of glutamyl residues on certain bone proteins, such as osteocalcin. Essentially, vitamin K helps these proteins hold on to calcium.

Research has shown associations between high serum concentrations of undercarboxylated osteocalcin, low serum concentrations of vitamin K, low bone mineral density and increased risk of hip fracture. In fact, according to, women with higher vitamin K intakes have a lower risk of hip fractures. Coincidently, women with the highest lettuce consumption (which is high in vitamin K) also have about half the risk of hip fracture. A higher intake of vitamin K in postmenopausal women also has been shown to increase the body's ability to make bone, and to slow the process of bone breakdown.

The Advantages of K, Safely

One of the concerns about vitamin K supplementation is its ability to accumulate in the liver (as it is a fat-soluble vitamin), and its low absorbability. However, a new form of vitamin K, introduced by Blue California, overcomes these issues. Vitamin K2 does not concentrate in the liver, and it is about 10 times more absorbable than other vitamin K forms. For example, vitamin K1 (also called phylloquinone) is found naturally in plants but offers only about 10% absorption rate. Vitamin K3 (or menadione) is synthetically made and is thought to be more toxic because it generates free radicals. A more natural alternative, the new vitamin K2 (also known as menaquinone) is made by the bacteria that line the gastrointestinal tract.

According to Cecilia McCollum, vice president of sales and marketing for Blue California, “Vitamin K is also found in high amounts in the Japanese traditional food called natto.” Natto is a sticky, fermented soybean food that can provide several milligrams daily of vitamin K—far exceeding the levels found in leafy greens. The company's vitamin K2 is from a vegetarian source, may enhance the probiotics in the gastrointestinal system and may have fewer interactions with medicines (such as the anticoagulant, coumadin). High vitamin K intake generally is not recommended for people taking blood thinners. However, McCollum adds that vitamin K2 is suitable for a wide range of dietary supplement applications, including bars, powdered drinks and tablets. NS

For more information:

Blue California, Rancho Santa Margarita, Calif.

Cecilia McCollum • 949-635-1990