Vitamin K not just for blood clotting

Natto, photo by Kinchan1 via Wikimedia Commons

Natto, photo by Kinchan1 via Wikimedia Commons

Interview with Christopher Speed, MND, APD

Vitamin K probably isn’t something you think about much, unless you’re one of the millions of people taking anti-coagulants.  In that case, you’ve likely been told to limit intake of high vitamin K foods, such as spinach or kale.  But thanks to recent research, knowledge of vitamin K — more specifically the family of phylloquinone molecules — suggests there’s a lot more to vitamin K than blood clotting.  In fact, a separate form of vitamin K may play a critical role in two major chronic disease processes: heart disease and osteoporosis.

Radio Nutrition recently spoke with Christopher Speed, MND, APD, Associate Editor of the European Journal of Cancer Prevention, and  adjunct Lecturer at New York University Nutrition School.  He has expertise in communications about novel nutrients such as omega-3 and vitamin K, and works on health and wellness communication for many prominent food, nutrition, and supplement companies.  He discusses some of the new thinking about vitamin K, in particular vitamin K2.  The podcast includes additional thoughts and discussion about vitamin K2, including surprising information about a significant food source.

Radio Nutrition: Most people think of vitamin K as one molecular type, important for blood clotting.  What are the different types of vitamin K, and the other key roles vitamin K plays?

Chris Speed: Although the name suggests differently, vitamin K is not a single compound. It consists of a group of fat-soluble vitamins that are essential for the body to have normal coagulation, or blood clotting, as well as to utilize calcium for healthy bones, arteries and soft tissues. The vitamin K family is divided into vitamin K1 – one molecule (phylloquinone) – and vitamin K2 – a group of molecules (menaquinones).

While Vitamin K1 is needed for proper blood coagulation, vitamin K2 is essential to build and maintain strong bones, as well as to avoid calcium deposits in the arteries, promoting cardiovascular health. Vitamin K2 exists in several forms, the most common ones are the synthetic menaquinone-4 (MK-4) and the natural or synthetic menaquinone-7 (MK-7).

All K vitamins are similar in structure: they share a “quinone” ring.  However, they differ in the saturation and number of attached carbon-hydrogen atomes in the sidechain — called “isoprenoid residues.” These differences are especially pronounced in the vitamin K2 group, which includes menaquinones with different lengths of the side chain.  The length influences their abilities to reach different tissues within the body: the longer side chain, the better its potential.  Consequently, the superior amongst all K vitamins are the long-chain menaquinones — especially MK-7.  They are completely absorbed, and remain in the blood for the longest time, and are therefore more available for all tissues when needed.

Where bone health is concerned, Vitamin K2 activates osteocalcin, a protein required to bind calcium to the mineral matrix, thus strengthening the skeleton. In circulation, Vitamin K2 allows the Matrix Gla Protein (MGP) to accomplish its desired goal: taking calcium away from the arteries (where it could have calamitous effects) and putting it in the bone (where the effects are far more beneficial).

Due to vitamin K’s activation of MGP and osteocalcin, calcium is ushered away from the arteries (high calcification correlates to increased death from cardiovascular disease), directing it and binding it to the bone mineral matrix. So the better one’s K status, the better their heart and bone health.

Radio Nutrition: Given that there are different forms of vitamin K, is it important for people to consume the different forms, or can simple vitamin K1 from green vegetables satisfy all requirements?

Chris Speed: Vitamin K2’s supremacy comes from its different sidechains.  Scientific findings have shown that vitamin K1 cannot deliver all of vitamin K2’s benefits because it lacks the side chain. Vitamin K1 and vitamin K2 can both act as enzyme cofactors*, but K2 is much more bioavailable and bioactive and more effective in supporting this enzymatic process. In addition to its function as an enzymatic cofactor, vitamin K2 has a dual role in mediating bone homeostasis – it acts to stimulate the synthesis of bone, while also decreasing bone resorption (removal of calcium).  Finally, studies have shown that only long-chain menaquinones are cardioprotective.

Radio Nutrition: Are current recommended intake levels adequate?  How are they assessed and how is the recommended intake set?

Chris Speed: There currently are no recommended intake levels for vitamin K2 – the only recommended levels are for vitamin K1 at this point, and vitamin K1 does not deliver the same benefits as vitamin K2.

While benefits have been demonstrated in studies where adults supplemented K2 as MK-7 at 180 mcg/day and children supplemented K2 as MK-7 at the 45-50 mcg/day level, the need to improve K2 status warrants further discussion to establish whether this dose is adequate.

Radio Nutrition: What type of diet would likely provide an adequate intake?

Chris Speed: While vitamin K1 is found in green leafy vegetables, such as broccoli, spinach and kale, and is easy to incorporate into one’s diet, the more beneficial vitamin K2 is difficult to come by through diet alone.

Natural vitamin K2 is found in bacterially fermented foods like mature cheeses and curd. The MK-4 form of vitamin K2 is often found in relatively small quantities in meat and eggs. The best source of natural vitamin K2 is the traditional Japanese dish “natto,” which is made of fermented soybeans. Natto provides an unusually rich source of natural vitamin K2 as long-chain menaquinone-7.

Epidemiological trials show the benefits of eating food rich in vitamin K, especially vitamin K2, and the positive health impact on the populations and cultures regularly consuming traditional food sources of vitamin K.

In one such trial of a Dutch population, the dietary intake of phylloquinone (K1) and menaquinone (K2) was followed by 4,807 subjects for seven to 10 years. The relative risk of mortality due to coronary heart disease was reduced significantly with increased intake of dietary menquinones (K2) from food such as cheese, but not with intake of phylloquinone (K1) from vegetables.  For another epidemiological study, the health status of 944 Japanese women (aged between 20 and 79 years) was followed for three years, and natto intake was suggested to be responsible for preventing post-menopausal osteoporosis due to the effects of MK-7.

Even though studies have found that natto consumption in Japan has been linked to significant improvement in K vitamins status and bone health, the intense smell and “controversial” taste make this soy food a less attractive source of vitamin K2 for the Western population. Therefore, supplementation offers a viable alternative to receiving adequate vitamin K2.

Radio Nutrition:  What is the current typical form in supplements?  How does the product, MenaQ7® differ?  Does this form of vitamin K differ from the types found in food?

Chris Speed: While it is a noble to try to attain K2 through the diet, the typical Western diet contains insufficient amounts of vitamin K2 to adequately activate MGP, which means about 30% of vitamin K2-activated proteins remain inactive.  This amount only increases with age.  Further, vitamin K2 is nearly non-existent in processed “junk” food, and even in a healthy Western diet.

Due to the deficiency of K vitamins in most people eating a Western diet, supplementation might be helpful. Vitamin K2 intake has been linked to both bone and cardiovascular health, and the most desirable form of K2 is natural vitamin MK-7 form.  This is the most bioavailable, bioactive and longest lasting form of vitamin K available.  One MK-7 product — called MenaQ7® from NattoPharma — has been tested by VitaK Research at the Maastricht University in the Netherlands, the world’s largest research institute dedicated to vitamin K, for safety and efficacy in humans.

Despite the strong epidemiological evidence showing that dietary intake of vitamin K2 may improve overall health status, it was not until a three-year ‘breakthrough’ study of MenaQ7® – completed in 2012 – that there had been a clinical trial to show that only a long-term (more than one year) supplement of vitamin K, especially MK-7, improves bone mineral density, bone mineral concentration and bone strength.  The study was a double-blind, randomized, clinical trial evaluating the results of a three-year regular intake of natural MK-7 in a 180 mcg daily dose by a group of 244 healthy post-menopausal Dutch women, 55 to 65 years old, randomly assigned to receive either MenaQ7® or identical-looking placebo capsules, daily.

This study is considered by the medical community to be a breakthrough because it shows clinically, for the first time, statistically significant protection with vitamin K against osteoporosis and cardiovascular deterioration with aging. Specifically, with regards to bone preservation, the study showed significant protection of the vertebrae and the hip (femoral neck) against osteoporosis and fractures due to bone degeneration. This was achieved with only 180 mcg/daily of MenaQ7®, which is considered a ‘nutritional dose,’ meaning it is a dose that can be obtained from a healthy balanced diet.  Importantly, the three-year study showed, for the first time, substantial benefits of nutritional vitamin K2, as compared to the placebo group, in preventing age-related stiffening of arteries.

Radio Nutrition: What are the considerations for people on anti-coagulant therapy regarding vitamin K?   What objections might the medical community have about a vitamin K supplement for these people? 

Chris Speed: Avoiding unwanted calcification and simultaneously keeping bones healthy is important for millions of people all over the world. It is vital to know that natural vitamin K2 is safe. Present studies show that 45 μg MenaQ7® does not interfere with blood-thinning medicines, and as such MenaQ7® does not provoke any additional risk of clot formation inside blood vessels.  However, a person using the blood thinning medicines coumarin or warfarin should consult his or her physician for options.

NOTE: while MenaQ7® is produced by NattoPharma, I was not reimbursed in any way for posting this interview.

*for the γ-carboxylase that facilitates the post-translational conversion of glutamic acid to γ-carboxyglutamyl (Gla) residues

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