When Your Doctor’s Good Intention is Bad Advice
Vitamin K is an excellent example of this, and of how many conventional docs have it all wrong. Vitamin K is a category of nutrients that includes vitamin K1 and vitamin K2. Vitamin K2 is also a category, which contains different types of vitamin K2. The form of vitamin K2 that has been most studied to grow stronger bones in people with osteoporosis and for helping to promote cellular health in people with certain cancers is the MK4 form of vitamin K2. More than 25 clinical trials and shown to stop and reverse bone loss and reduce fracture risk more than 80%. And 14 studies evaluated the ability of MK4 to promote healthy cells in people with cancer.
The dose of MK4 used in the studies for bone health and cancer support has consistently been 45 mg per day, and up to 135 mg per day in people with cancer. In total, more than 7,000 people have taken 45 mg or higher of MK4 for up to eight years, so there are excellent health and safety data on MK4.
The U.S. Institute of Medicine (IOM) has established the adequate intake of vitamin K to be 90 mcg per day for women and 120 mcg per day for men. Adequate intake is the amount of a nutrient believed sufficient to prevent a deficiency; however, adequate intake is not the optimal amount to promote health is typically based on a limited number of health indicators.
For vitamin K, the adequate intake amount is based on the ability of vitamin K to promote healthy blood clotting. While vitamin K is essential for blood clotting, vitamin K, like other nutrients, has many other functions in the body. In addition to blood clotting, vitamin K is involved in growing healthy bones, producing healthy nerves and sustaining healthy blood.
The amount of MK4 used in studies is 45-135 mg, which is 500 to 1,500 times greater than the IOM adequate intake. Thus, an important question is whether or not it’s safe to consume vitamin K at this high dose. The short answer is unambiguously, Yes. MK4 is safe even at doses much higher than the top amount used in clinical trials.
The Tolerable Upper Limit (TUL) is the highest daily dosage that is safe for almost all individuals in the general population to take on an ongoing basis. The IOM concluded that for natural forms of vitamin K, of which MK4 is one, there is no known TUL. This means that the IOM considers vitamin K to be extremely safe, even at very high doses.
Another indicator of safety is the LD50. The LD50 is the amount of a substance that kills 50% of the laboratory animals. LD stands for “lethal dose.” The US National Institutes of Health (NIH) lists the LD50 for oral MK4 as >5 grams/kg body weight. One gram is 1,000 times more than 1 milligram (mg). To make this more applicable to a real person, if someone weighs 120 pounds, the LD50 would be greater than 270 grams of MK4. That is 6,000 times the amount of MK4 used in most clinical trials (45 mg/day MK4).
Although the research shows MK4 to be safe even at extremely high doses, some conventionally trained healthcare providers can become alarmed at a product that delivers 45 mg/day MK4. They may erroneously believe that this amount of vitamin K is dangerous and will increase a person’s risk for blood clots.
The logic of their false conclusion is as follows. Vitamin K is used to promote blood clotting. Therefore, if someone takes more vitamin K it will promote blood clotting even more and increase someone’s risk for dangerous blood clots. While they may be speaking from a place of concern for the health of their patients, they’re wrong about vitamin K.
The fact is, once the body has enough vitamin K for healthy blood clotting, the body can’t create excessive blood clots. It just doesn’t work that way. It’s like a conveyor belt. Once it’s going at full speed it can’t go any faster. The vitamin K simply goes on and does other beneficial things in the body. The safety of MK4 on blood clotting has been shown in studies. One clinical trial using 135 mg per day of MK4 concluded that blood clotting remained normal and no adverse reactions were observed. And of the dozens of clinical trials of MK4 at dosages of 45mg per day, conducted for as long as 6 years, and up to 135 mg per day, none have reported any problems with blood clotting, and in fact have reported the complete absence of serious side effects.
There is one group of people, however, who should not take MK4. Those are people who are taking the drug warfarin (Coumadin). Warfarin is a blood thinner the works specifically by blocking vitamin K’s actions in the blood clotting cascade. Providing vitamin K as a dietary supplement can antidote the warfarin. People taking warfarin should absolutely not take MK4 and they shouldn’t take any vitamin K-containing products without first consulting their healthcare provider.
Cockayne S, Adamson J, Lanham-New S, Shearer MJ, Gilbody S, Torgerson DJ. Vitamin K and the Prevention of Fractures: Systematic Review and Meta-analysis of Randomized Controlled Trials. Arch Intern Med. 2006;166(12):1256-1261. [Article]
Miyazawa K, Nishimaki J, Ohyashiki K, et al. Vitamin K2 therapy for myelodysplastic syndromes (MDS) and post-MDS acute myeloid leukemia: information through a questionnaire survey of multi-center pilot studies in Japan. Leukemia. 2000;14(6):1156-1157. [Article]
Substance Name: Menatetrenone [INN:JAN]. U.S. National Institute of Medicine TOXNET Toxicology Data Network. Accessed February 5, 2018. [Web page]
U.S. Institute of Medicine Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. Washington (DC): National Academies Press;2001. [Report]
Ushiroyama T, Ikeda A, Ueki M. Effect of continuous combined therapy with vitamin K(2) and vitamin D(3) on bone mineral density and coagulofibrinolysis function in postmenopausal women. Maturitas. 2002;41(3):211-221. [Article]
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