We learned in last week’s blog post how vitamin K2 is a calcium mover in the body and can help with both osteoporosis and atherosclerosis. Let’s check a little more into Vitamin K2 sources, both food and supplements, and see how much we need to get these beneficial effects. 

As we mentioned in our first K2 blog post, there are two primary food sources of vitamin K2 – grass-fed animals, and bacteria (fermented foods). Let’s look at how much we can get from foods.

Vitamin K2 sources – Food 

Here is a list showing the average amounts of vitamin K2 content (in micrograms) per 100g in foods with the highest K2 levels. (Where animal products are included in the following list, the values are for pasture raised animals.)

  • Natto 1,100mcg 
  • Goose liver pate 370mcg 
  • Gouda cheese 76mcg 
  • Brie cheese 56mcg 
  • Egg yolk (each yolk) 32mcg 
  • Butter 15mcg
  • Chicken liver 13mcg 
  • Chicken breast 9mcg 
  • Sauerkraut 5mcg 

Hmm. These high sources of vitamin K2 are all pretty rich foods. Looking at this list makes me think of the “French Paradox” – where the French diet is seen to be indulgent in rich foods such as foie gras, pates, cheeses, eggs, and buttery sauces, yet they have relatively good heart health. Maybe the K2 content is part of this picture?

So a couple of eggs a day would give us around 60mcg K2 or 2 ounces of Gouda cheese would give us about 35mcg of K2. Is that enough? Is it too much? Do we need this every day?

How much vitamin K2 do we need? 

Current daily recommendations for K vitamins are based exclusively on vitamin K1 and the requirement for proper blood clotting. These levels are 120mcg Vitamin K1 for men and 90mcg for women, daily – but you will frequently see them reported as “Vitamin K.” Remember, this is K1, not K2. 

However, while it is now acknowledged that the general Vitamin K1 (or ‘Vitamin K’) level is inadequate for BOTH K1 and K2, Vitamin K2 does not have its own RDA (recommended dietary allowance). This might partly be due to its recent characterization, and thus there is less research evidence.

Whatever the reason, we still wait for recommended daily levels for vitamin K2. 

So how can we figure out today how much we need? We need to look at the research and see what that says.

Highlights from the research

There is so much I could go into here about what the research shows –  both food research and supplement research – but you don’t need to know all the nitty gritty. So here are the highlights:

  • K2 is not toxic – considered to be partly due to it not being stored in the liver. 
  • There are different forms of K2 known as MK4, MK5, MK6, all the way to MK10.  The diagram at the top shows how the number just relates to the size of the chemical structure.
    • Grass fed meats generally contain MK4. Natto contains MK7. Fermented foods generally contain a mix of MKs. Supplements are either MK4 or MK7.
    • All MKs seem to have the same function.  
    • The larger the MK number, the longer it stays in the body.
    • The larger the MK number, the less we need.
    • Research seems to suggest that with supplements we need a lower dose of MK7 than MK4, and need MK7 only once a day, as opposed to three times a day for MK4.
  • While we see beneficial effects of dietary K2 in studies, it is difficult to evaluate the amount consumed and absorbed accurately.
  • Research on supplementation seems to give us more tangible results on which to base our daily requirements:
    • Results from research studies using MK4 suggest effective dose levels of MK4 be 45mg per day – but taken as 15 mg three times a day.
    • Research on MK7 shows effective dose levels to be 100-180mcg per day, taken once a day. Note 1 mg (milligrams) is 1000 mcg (micrograms). Don’t confuse mg with mcg. 

So do you need to supplement?

How can I tell what my K2 levels are?

While symptoms and food intake can suggest possible deficiencies, it’s helpful to know your own blood levels of K2 to determine if you need to supplement or increase your dietary intake. I recommend working with a health care practitioner who is familiar with nutrient and micronutrient requirements.

K2 levels can be measured as part of the Spectracell Micronutrient test.  Unfortunately, few other testing options are available apart from those used for research purposes. 

K2 dietary levels

If we don’t know our blood levels, we can look at our food intake and make an estimate on what we get each day.  

As a very rough guide, if you eat a pack of natto (40g) at least four days a week, you will have enough K2 – about 200mcg MK7 daily!!! Let’s all rush out and get some! Yuck!

Otherwise, without natto, we need to eat several of the other foods on the list above each day to get adequate levels.

Or we could supplement to ensure healthy levels. 

MK7 supplement studies

As stated above, it seems the best form of supplemental K2 might be MK7.  

In the last couple of years, several studies, including the following, have investigated MK-7. The most researched form of K2 MK7 is a form called MenaQ. Here is what some of the studies have shown:

  • In a double-blind, randomized intervention trial, the researchers found that three years of daily supplementation with 180 mcg of Vitamin K2 as MK7 (as MenaQ) not only inhibited age-related stiffening of the artery walls but also made a statistically significant improvement in vascular elasticity, especially in women having high arterial stiffness.
  • Using the same dose level and type of MK7 as above, 180mcg of MK7 for three years resulted in improvements in both bone mineral content and bone mineral density. It also decreased the loss in vertebral height in the thoracic region in post-menopausal women.
  • An MK7 (as MenaQ) fortified yogurt drink was used in a study on healthy men and postmenopausal women. Results showed that MK7 was efficiently absorbed from the fortified yogurt, improved vitamin K2 status, and contributed to improved cardiovascular health. 

Further information on MenaQ studies can be found here: MenaQ studies.

Recommendations

As most of the most recent research is on MK7 MenaQ, this is the form I tend to recommend, as we have the most data on its safety and effectiveness. 

For general health maintenance, it seems prudent to supplement with K2 at a dose level around 100-150mcg/day of MK7. This is unless you regularly consume foods containing reasonable levels of K2, in which case you can reduce the supplement level accordingly.

For the indications listed below, it might be worth considering taking higher dose levels of K2 (150-180mcg/day of MK7) for several months to try and re-establish the distribution of calcium in the body, before going down to a maintenance dose. Indications that suggest a higher dose level include:

  • taking or have taken calcium supplements – particularly in post-menopausal women
  • osteoporosis or osteopenia
  • a history of cardiovascular disease or family history of CVD
  • taking statins
  • recently taken broad spectrum antibiotic for a considerable period
  • a presence of bone spurs
  • psoriasis
  • prostate issues
  • prostate or lung cancer
  • insulin resistance
  • dental caries
  • varicose veins
  • taking bile acid sequestrants

The MenaQ product I use, because I don’t like taking capsules, is FLOZ NutriK2. It’s a liquid with no taste, containing 150mcg MK7 per dropper. It also contains vitamin D3 and vitamin A which help in the calcium carrier function.  

If you prefer a capsule, Doctor’s Best Artery Prime has 180mcg MK7 plus vitamin D, or Doctor’s Best Vitamin K2 in the UK – 100 mcg MK7 alone. 

Check your multivitamin too – that might already have adequate vitamin K2 in it.

All these supplements are best taken with food to help their absorption. 

Vitamin K2 partners

As mentioned above, the two principal partners of vitamin K2 are vitamins D and A. These are both involved with the calcium action of K2. For this reason, we should make sure that we obtain vitamins K2, D, and A during the same day either from foods or supplements. (Doesn’t have to be at the same time of the day, but during the same day.) 

Contraindications

The anti-coagulant Warfarin interferes with vitamin K – both K1 and K2. It is recommended that you don’t take vitamin K supplements while taking warfarin. This interaction is not seen with other anti-coagulants so check with your doctor, as it might be appropriate if you are using some other anti-coagulant to continue your vitamin K supplements too. 

Without an RDA for vitamin K2, it is complicated to know what to do. I hope today’s post helps, but if you have specific questions, do email me or ask in the comment section below. 

In the next blog post, we’ll look at K2 and prostate cancer and varicose veins.  

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