As more and more people discover that vitamin K helps naturally strengthen our bones and protect our hearts, I’m frequently asked how to get the optimal benefit from this key nutrient. Here are answers to the most common questions I hear:
1. Why do I so strongly recommend supplementation of vitamin K?
For most of us, our current dietary intake of vitamin K is too low to have the proper calcium utilization that keeps calcium in the bones and out of our arteries. Vitamin K facilitates the transport of calcium from the bloodstream into the bone and is essential for the proper formation of “osteocalcin,” a bone-formation protein. It also prevents arterial calcification.
2. What is the difference between the various forms of vitamin K and which form do I prefer?
The two main forms of vitamin K are K1 and K2:
• K1 (phylloquinone) is abundant in green leafy vegetables. This form of vitamin K has a short half-life within the body, being rapidly cleared by the liver. A small amount of K1 is commonly used in multivitamin formulations and a deficiency of vitamin K1 leads to defective blood clotting.
• K2 (menaquinone) is found in meat, eggs, and some dairy products. Vitamin K2 is produced by bacteria found in aged or fermented foods such as natto, aged cheese, and sauerkraut. Certain forms of vitamin K2 are now being introduced into selected nutritional supplements.
The subtypes of vitamin K2 are known as MK-7 and MK-4. More and more, these are being incorporated into nutritional supplements, so let me explain a bit about the vitamin K2 family.
• Vitamin K2, in the form of MK-7 (menaquinone-7) has a long half-life within the body, being evident even 72 hours after ingestion. Small supplemental or dietary doses of the potent MK-7 (180 mcg) have been found effective in reducing menopausal bone loss, strengthening bone, and reversing arterial calcification. To date no fracture trials have been done with MK-7, but the Japanese populations that consume this nutrient through a high intake of fermented soy called “natto” exhibit a reduced incidence of both fracture and heart disease.
• Vitamin K 2 as MK-4 (menaquinone-4) is found in small amounts in foods such as butter, egg yolks, and meat, and it has a short half-life within the body. A form of very high-dose synthetic MK-4 has been developed as an osteoporosis drug by the Japanese. When used as a bone drug, MK-4 must be taken in the high dose of 15 mg, three times a day. Studies suggest this K2 supplementation effectively reduces fracture risk.
With the Better Bones approach, we encourage everyone to eat at least two cups of green leafy vegetables per day. These vegetables will provide a good amount of the plant-based K1. While vitamin K1 is important, research supports the special value of vitamin K2 as MK-7. We use MK-7 supplements that are naturally derived from fermented foods such as soy (“natto”) in the dose of 90 to 300 mcg per day.
The synthetic vitamin K2 as MK-4 mentioned above is given in high pharmacological, not physiological doses (45 mg/day). At the Center for Better Bones, we have great success with small dietary level doses of MK-7 and rarely find the need to use this high dose MK-4 bone drug.
3. Is it safe to use doses of vitamin K that are well above the RDA?
The RDA for vitamin K, as in all nutrients, is the established level which will prevent deficiency disease in a majority of the population. Unfortunately, the RDA tells us nothing about the level that will promote optimal health. Happily, vitamin K is extremely safe when consumed in levels many, many times its RDA. The only exception is for those on the blood thinner Coumadin because supplementing with vitamin K will reduce the effectiveness of Coumadin.
For more information on the benefits and safety of vitamin K, I suggest you review any of the 261 articles by world-renowned vitamin K researcher, Dr. Cees Vermeer here.
I’m Dr. Susan Brown. I am a nutritionist, medical anthropologist, writer, and speaker. Get my free weekly newsletter here.