A key word above is natural K vitamins, there is an artificial form called K3 and that is toxic in high doses, it is not sold for human consumption.

Of interest in that document the FAO and WHO also stated the following regarding future research on vitamin K;-

“Future research
The following are recommended areas for future research:
• prevalence, causes, and prevention of VKDB in infants in different population groups;
• bio-availability of dietary phylloquinone (and menaquinones) from foods and
menaquinones from gut flora;
• significance of menaquinones to human requirements for vitamin K;
• the physiologic roles of vitamin K-dependent proteins in functions other than coagulation;
and
• the significance of under-carboxylated vitamin K-dependent proteins and sub-optimal
vitamin K status to bone and cardiovascular health”

This was written in 1998 and many interesting studies have appeared since then. Of the 5 points raised I would say that the evidence is:-
1. Adequate intake of vitamin K by the mother is vital for the development of foetuses and newborn children. It looks vital for development of children.
2. Menaquinone doesn’t seem to be highly available from the gut, if it was then all the vitamin K dependent proteins in the body would be activated. However it has been found that only by increasing vitamin K intake can this be done.
3. It looks like the menaquinones are vital to prevent diseases associated with aging. Phylloquinone (K1) is very good but doesn’t quite work the same.
4. The vitamin K dependent proteins are linked to the prevention of many illnesses.eg Matrix gla proteins – CVD, arthritis, glaucoma. Osteocalcin – osteoporosis, diabetes mellitus, Nephrocalcin – kidney stones (kidney health?) Periostin – asthma, dental health, arthritis, wound repair (ulcers?). Transforming Growth factor Beta induced (tgfbi) – Cancer, cornea. Protein C – deep vein thrombosis, sepsis, inflammation, cancer. Protein S – deep vein thrombosis, sepsis, inflammation. GAS6 – nervous system.
5. Under carboxylated and suboptimal vitamin K status is very significant for cardiovascular health and osteoporosis.
I would mention one study for reference for some of the above “Vitamin K, an example of triage theory: is micronutrient inadequacy linked to diseases of aging?” [2]
Though a lot more research is needed in order gain a clearer understanding of the exact benefits of vitamin K.

Coming back to vitamin K toxicity, there was a study on a synthetic manufactured form of MK7 which showed that a single oral dose of 2000 mg/kg body weight in mice had no observable toxicity during the 14 days observation period. This dose is equivalent to a 75 kg person taking 150,000,000 micrograms of K2. Rats given 10 mg/kg body weight for 90 days again showed no adverse effects, this is equivalent to 750,000 micrograms a day for a 75 Kg person. [3]
People have been taking 45 mgs/day of K2 (MK4) for years in Japan to treat osteoporosis. Some adverse effects have been reported eg skin rash, stomach discomfort, headache. Though as far as I know there hasn’t been a double blind study and so one cannot be certain that the 45 mgs of K2 necessarily caused the issues or whether it is caused by the other substances in the capsules. [4]

However with all these issues you have to weigh up the evidence and decide for yourself.

Regarding your diet, green leafy vegetables are great; apart from K1 they have a lot of other beneficial nutrients. However K2 does seem to have benefits beyond what can be achieved from k1. Yogurt would have K2, though the evidence is that full fat would contain much more K2. Fermented cheese is another great source of K2 and it is a much better source than meat (apart from possibly liver).

People have and do overdose on vitamin supplements; however vitamin K2/K1 does seem to be pretty safe. I tend to be more concerned about the other ingredients/fillers in the capsules/tablets.

[1] Human Vitamin and Mineral Requirements 1998
FAO UN / WHO
[1] ftp://ftp.fao.org/docrep/fao/004/y2809e/y2809e00.pdf

Am J Clin Nutr. 2009 Oct;90(4):889-907. Epub 2009 Aug 19.
[2] Vitamin K, an example of triage theory: is micronutrient inadequacy linked to diseases of aging?
McCann JC, Ames BN.
http://www.ncbi.nlm.nih.gov/pubmed/19692494

Toxicol Mech Methods. 2011 Sep;21(7):520-32. Epub 2011 Jul 25.
[3] Safety and toxicological evaluation of a synthetic vitamin K2, menaquinone-7.
Pucaj K, Rasmussen H, Møller M, Preston T.
http://www.ncbi.nlm.nih.gov/pubmed/21781006

[4] Glakay Vitamin K2 Capsules 2009
http://www.eisai.jp/medical/products/di/EPI/GLA_SC_EPI.pdf

I hope this helps.

I guess my initial question would be about K remaining in the liver. I wouldn’t think it is toxic, but is it possible to overload the liver with K?

I eat plenty of green leafy veggies and yogurt but no meat. I do eat fish but am unsure if it’s a great source for K. Given my dietary habits, it would seem I should use a K supplement. I”ll look into this a bit further.

I find this information fascinating. Thanks for being such a great resource.

Firstly a very important thing to remember with vitamin K is that it is fat
soluble. No matter what form you take vitamin K in, if it isn’t consumed
with fat you will not absorb it well and you will not get the benefit or
indeed the benefit of any other fat soluble nutrient.
I know fat has been vilified as unhealthy, however modern studies have shown that fat (apart from transfats) have been found to be healthy or neutral. I would refer to the nutrition section of the American Heart Association publication Heart Disease and Stroke Statistics 2012 which
states the following:-
…………….
In the WHI randomized clinical trial (n_48 835), reduction
of total fat consumption from 37.8% energy (baseline) to
24.3% energy (at 1 year) and 28.8% energy (at 6 years) had
no effect on incidence of CHD (RR 0.98, 95% CI 0.88–
1.09), stroke (RR 1.02, 95% CI 0.90 –1.15), or total CVD
(RR 0.98, 95% CI 0.92–1.05) over a mean of 8.1 years.67
This was consistent with null results of 4 prior randomized
clinical trials (below) and multiple large prospective cohort
studies (below) that indicated little effect of total fat
consumption on risk of CVD.68

In a pooled analysis of individual-level data from 11
prospective cohort studies in the United States, Europe, and
Israel that included 344 696 participants, each 5% higher
energy consumption of carbohydrate in place of saturated
fat was associated with a 7% higher risk of CHD (RR 1.07,
95% CI 1.01–1.14).72 Each 5% higher energy consumption
of monounsaturated fat in place of saturated fat was not
significantly associated with CHD risk.72

In a meta-analysis of prospective cohort studies, each 2%
of calories from trans fat was associated with a 23% higher
risk of CHD (RR 1.23, 95% CI 1.11–1.37).74
……………..

So saturated fat doesn’t cause heart disease, and saturated fat is healthier
than carbohydrates with regard to heart disease. The theory that fat caused
heart disease was interesting but has been found to be wrong; unfortunately
this fact hasn’t got widespread publicity. Statistics from Europe show
that the European countries that eat the most fat have the longest life
expectancy and the least heart disease (this is also true with regard to the
consumption of saturated fat). As you noted elsewhere the truly nasty fats are the manufactured
trans fats, they really should be banned

Coming back to vitamin K.

Dietary Sources of vitamin K

K1 – Green vegetables (plus butter or olive oil)
K2 (MK-4) – Meat (there is more K2 in meat from grass fed animals since K1 is converted to K2), egg yolk
K2 (MK -7,8,9) – Cheese, yogurt (full fat), and probably also liver.
Fermented soy beans. (Note: The cheese/yogurt should be made from milk from grass fed animals and be well fermented.)

Eating food containing K2 and K1 is definitely recommended. The longer
chained menaquinones MK7, MK8, etc seem to be more effective.

Vitamin K Supplements

K1 ; it helps ensure your clotting works correctly. K1 doesn’t last long in
your blood stream, it ends up in the liver and stays there. Trials have used
doses of 500 to 4000 micrograms.
K2 (MK-4) : it is sold in large doses eg 5,000 microgram and 45,000
microgram, these are doses well above anything you could receive naturally.
MK4 doesn’t last long in your blood stream. The 45 milligram amount is being
used in Japan for osteoporosis.
K2 (MK-7): it is available in capsules ranging from 45 micrograms to 100
micrograms. Like the other forms of vitamin K in ends up in the liver, but
unlike the other forms it leaves the liver, re-enters the blood stream and
continues to supply other organs for 72 hours.
If you are taking K daily then the MK 7 form does ensure that your body has
vitamin K available when it is needed. In terms of quantity, trials have
been carried out using 45 micrograms to 360 micrograms. A couple of recent
successful trials on bone health have used 100 micrograms of MK7, trials
looking at arterial calcification prevention are using between 180 and 360
micrograms of MK7.

Many more studies are needed to determine the optimum amount and type of
vitamin K needed for health. I am taking about 300 micrograms of MK7 per
day, I tend to go for the oil filled capsules since there is less ‘filler’,
though I have also taken the Life Extensions ‘Advanced K formula’ which has
a mix of the three main available forms of vitamin K. Other people I know
are taking between 100 to 200 micrograms of MK7. I would note that one of
the most commonly reported effect is the disappearance of knee
pain/osteoarthritis. (yes, there are studies linking vitamin K to less knee
osteoarthritis )

I hope this helps, and please let me know if you have any questions.

Stew

Yesterday I was in the health store stocking up on some of my vitamins and saw vitamin K. The only reason I didn’t buy it was because in the back of my mind I remembered you mentioning vitamin K1 and K2. I couldn’t remember which one we get naturally in green leafy veggies and which one we didn’t.

Instead I opted for Tumeric to help with the body’s inflammation, but I’d like to look further into vitamin K. Vitamin K is something I’d like to incorporate in my diet, but I’d rather supplement the form of K in which I’m deficient. Any advice?