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What are the best sources of vitamin K?

I have read in a magazine that there are several types of vitamin K. According to the article, Vitamin K1 is found in vegetables. Vitamin K2 mk7 is found in meat, fish and eggs. The article also said that Vitamin K1 is stored in the liver for only one hour, time not enough to perform all its tasks. On the contrary, vitamin k2 mk7 would stay in the liver for the whole day. So my question is: should vegetarians take supplements of vitamin k2 mk7 (created from natto)?

vjimener / Originally posted below Better than green tea?

Answer:

Not sure what magazine you were reading, but the scientific consensus is that either one (phylloquinone or menaquinone, formerly K1 and K2) is fine for maintaining human vitamin K status. The recommended intake is about 100 mcg. A half cup of kale? >500. No need for natto; just eat your greens.

In fact dark green leafies are so packed with vitamin K that if you’re on the drug coumadin (warfarin), a drug that works by poisoning vitamin K metabolism, you have to closely work with your physician to titrate the dose to your greens intake so as to not undermine the drug’s effectiveness!

Learn more about the wonders of greens in my 25 videos (like Eating Green to Prevent Cancer) and kale in particular in videos such as Smoking Versus Kale Juice and Kale and the Immune System.

Image credit: ilovemypit / Flickr

Dr. Michael Greger

About Michael Greger M.D.

Michael Greger, M.D., is a physician, author, and internationally recognized professional speaker on a number of important public health issues. Dr. Greger has lectured at the Conference on World Affairs, the National Institutes of Health, and the International Bird Flu Summit, testified before Congress, appeared on The Dr. Oz Show and The Colbert Report, and was invited as an expert witness in defense of Oprah Winfrey at the infamous "meat defamation" trial. Currently Dr. Greger proudly serves as the Director of Public Health and Animal Agriculture at the Humane Society of the United States.

View all videos by Michael Greger M.D.

  • Tony

    Isn’t vitamin K1 distinct from K2. K1 plays an important role in coagulation. K2 plays a role in directing where calcium gets stored. Too much calcium in the blood can cause calcification, K2 helps direct the calcium to the bones. If that is true, don’t we need to satisfy our requirements for K2 specifically? Sounds like we would need to be getting some natto after all.

  • adawe

    mk4 isn’t same as mk7 either. both are k2, but different forms

  • colonyofcells delacruz

    I like natto bec it is fermented and the vitamin k2 from natto is a nice bonus. I have been able to find low salt natto bec I don’t like any added salt. I have already decided to get rid of miso since I cannot find low salt miso.

  • Sharon

    I was reading K2 and Calcium Paradox and it indicates the only non-animal source of K2 is natto (which I don’t like). It also says K2 is not the same vitamin as K1.. ie. K2 prevents atherosclerosis, diabetes 2, cancer, and osteoporosis, etc, whereas K1 only helps with blood clotting. I tried researching on internet if this is true or quackery.. I don’t believe everything I read.. but so far have not found information on sites I would consider trustworthy.

  • Jeremy Nagel

    I think the research that Michael cited is out of date (published in 2009). I would suggest people read the review article “The role of menaquinones (vitamin K2) in human health” published in the Cambridge Journal of Nutrition in 2013. It states that Vitamin K2 has an important and distinct role in bone health. It also provides evidence that absorption of K2 produced by intestinal bacteria is very inefficient (because the K2 producing bacteria are located in the colon whereas K2 absorption happens in the small intestine). Therefore it recommends that everyone take a form of K2 every day, either from natto, animal products or supplements. (I’ve been taking a vegan K2 supplement sold by VitaCost.com).

    http://journals.cambridge.org/action/displayAbstract;jsessionid=8485084EC3B24DE5762B43FB087A1FBF.journals?fromPage=online&aid=8894242

  • Luc

    I strongly believe that vegan it is only possible to take profit from a vegan diet , rich in many useful nutrients, if we don’t turn a blind eye towards the downsides of not eating meat. Such as Vit D, Vit B12 , possibly Vitamine K(2) and who knows are there more …

    Vegans seem to have so much benefits , yet , no higher life expectancy proves that we are still missing some pieces of the puzzle, wood you agree to that ?
    So I am looking beyond what is served to me today.
    —–
    Maybe I found something here:

    I (53) have been taking Natto for a few weeks now and , waaw
    Before , being a vegan for over a year now, I can solve some of my healthissues but found it hard to make my bloodpressure move just a little bit…..

    Eating Natto , my bloodpressure 140/90 (150/100without medication ) just dropped to 110/80 (95/60 by moments). Waaw , this is not food , just a table spoon every day does more then medication. I am impressed. Yet it is not a structural solution to my high blood pressure.When I stop eating for a few days my BP goes up again.

    As for the longterm effects of other components in Natto , they remain to be seen, I am hopeful however to reduce some calcification in my arteries by eating Natto. More and more research from the past 10 years starts to indicate that it might be possible.

    K1(vegetables) and K2(from Natto) may have the same value in terms of directing calcium form our arteries towards our bones, K2 stays in our blood for days whereas K1 seems to be eliminated after few hours , hence we should eat tonnes of green leaves to keep up a certain level of K1 in our blood, while a tablespoon of Natto every day can do the trick 10 times better.

    (btw, I am not producer or selling Natto:) )

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