Vitamin K is well known as a blood clotting agent, without which, an injury could cause us to bleed to death.   In fact, vitamin K was named after the German word “koagulation”. However – there are two main types of K – K1 and K2 – and although most people get enough dietary K1 to maintain adequate blood clotting, they do NOT obtain enough K2, to perform its more recently discovered important functions / roles, including:

• Supports bone health (helps body utilize calcium in the right places)
• Keeps calcium out of blood vessels, cartilage and other soft tissue
• Boosts immune system function
• Ensures healthy skin
• Relieves menstrual cramps
• Enhances liver function
• Encourages the flow of urine
• Increases vitality and longevity (fights premature aging)
• Supports growth and development
• Provides powerful antioxidant benefits (Protects cells against oxidative damage)
• Boosts memory function
• Keeps your normal blood sugar levels normal
• Providing protection against:
• Arterial calcification, cardiovascular disease and varicose veins
• Brain health problems, including dementia
• Osteoporosis (maintains strong bones in the elderly)
• Cancer.    Especially Prostate cancer, Lung cancer, liver cancer and leukemia
• Tooth decay
• Diabetes / INSULIN resistance
• Infectious diseases E.g. pneumonia

Fat-Soluble vitamin K exists in two basic natural forms, K1 and K2.   Each now found to have quite DIFFERENT physiological functions:

(1) Vitamin K1 (PHYLLOQUINONE) – ~90% of vitamin K intake in typical Western diet

• K1 is preferentially used by the liver – where it helps maintain a healthy blood clotting system
• Found in leafy green vegetables. olive oil and other plant foods.   E.g. Brussels sprouts, Swiss chard, green beans, asparagus, broccoli, kale, leaf/romaine lettuce, cabbage, spinach, parsley, watercress, cauliflower and mustard greens. Cruciferous vegetables should be cooked to avoid suppressing thyroid hormone production.
• Adequate Vitamin K is important for those with blood type O.   Since type O’s lack several clotting factors in their blood

(2) Vitamin K2 (E.g. MENAQUINONE 4,7,8,9 thru 14).   ~10% of vitamin K intake in typical Western diet found in primarily fermented foods and aged cheeses; also produced by gut bacteria.

K2 is preferentially used by vessel walls, bones, and tissues other than your liver

• K2 beneficially directs calcium to be deposited in such as bones and teeth.   Conversely, prevents it from depositing in locations where it does not belong, such as the soft tissues

Spronk, H.M., Soute, B.A., Schurgers, L.J., Thijssen, H.H., De Mey, J.G., Vermeer, C., 2003. Tissue-specific utilization of menaquinone-4 results in the prevention of arterial calcification in warfarin-treated rats. J. Vasc. Res. 40(6), pp 531-537.

• Sperm contains a protein that relies on K2
• Your brain uses K2
• Saliva contains K2 to protect against tooth decay

K2 has several sub forms (with repeating 5-carbon units in the side chain of the molecule) – denoted as menaquinone-n or MK-n, where n is the number of 5-carbon units):

• MK-4 (menatetrenone). Found in organ meats, marrow, brain, and fish eggs; also butter fat from animals fed lush green grass or K-rich cereals (e.g. greens, alfalfa, wheatgrass); a little in egg yolks, a trace in meats; MK4 is now known to be Dr. Weston A. Price’s so-called “Activator X”. During the 1930’s, this Cleveland dentist traveled the world investigating the health of isolated primitive peoples. He found that when included in their diet, “Activator X”(K2 MK-4) not only kept people’s teeth free of tartar, but also prevented and healed cavities, and is needed for mineral utilization. Short half-life of about one hour -remains mostly in liver as a blood clotting agent.

MK-7,8, 9 and 10 come from bacterial fermentation.

• MK-7.   Found only in natto (not in the other more palatable fermented soy products e.g. miso and tempeh); The MK-7 form is longer acting (half-life of about 3 days) and is the usual supplement form (derived from natto).
• MK-8, MK-9, MK-10 and higher.   Found in meat, fish, dairy products

Beneficial gut bacteria (called probiotics) produce several sub forms of vitamin K2.   These lactic acid bacteria partially contribute to body’s K-status as the K2 is absorbed in small amounts from the distal small intestine (ileum).

• Broad-spectrum antibiotics have been shown to reduce vitamin K2 in the gut by nearly 74%.  Conly, J; Stein K (1994). “Reduction of vitamin K2 concentrations in human liver associated with the use of broad spectrum antimicrobials”. Clinical and investigative medicine. Médecine clinique et experimentale 17(6): 531-539. PubMed
• Probiotics also aid in digestion and assimilation of vitamins.   Including vitamin K . The best source of probiotics is fermented foods and drinks.

Probiotics

K2 sub forms found in animal foods (especially organs and pastured dairy), curds and fermented foods.    Many of them containing saturated fat:

• Natto, miso (fermented soybeans)
• Sauerkraut
• Hard and soft fermented cheese – E.g. Aged Goat cheese, Camembert, Blue Cheese, Stilton, Port du Salut, Feta, Aged Cheddar, Parmesan, Romano. (Provolone, Ricotta, and Mozzarella have no K2).
• Egg yolk
• Butter from grass-fed animals
• Chicken liver
• Salami
• Chicken breast
• Ground beef

Amount of K2 in fermented Foods is dependent on type of K2-producing bacteria used for fermentation:

• Cheeses –  E.g.Swiss Emmental cheese and Norwegian Jarlsberg cheese use the genus Proprionibacterium (creates CO2 bubbles that make the familiar holes in the cheese). These bacteria can make large amounts of vitamin K2 in the form of MK-9
• Fermented soy foods – the most important K2-producing bacteria are Bacillus genus, which create the MK-7 sub form of K2. Studies demonstrate that higher blood levels of MK-7 (obtained by consuming Bacillus in fermented soy) are associated with lower risk of hip fracture in older Japanese women. Natto has been an integral part of Asian cuisine for many centuries. Bacillus (E.g. B. subtilis var. natto strain used in natto production) has the potential ability to stay alive for several days in the lower intestine after consumption providing the body with MK-7.

Newborns are sometimes given K1 shots to prevent intracranial hemorrhage – to tide them over until at just over a week old, their intestinal bacteria produce K2 and the the infant has been ingesting K in colostrum, breastmilk or non-soy-based formula (contains more K than breastmilk);

Conversion of K1 to K2 in body?

Under ideal circumstances, gut bacteria or enzymes in cell metabolism can convert K1 from food and convert it into K2 – maintaining an optimal balance between the K1 and K2 forms of this vitamin. The mammary glands are especially efficient at producing K2 from K1, presumably to supply growing breast-fed infants.

Certain factors can interfere with the K1 to K2 conversion:

• Aging – Older individuals (over age 70) require higher levels of vitamin K.  Tsugawa N, Shiraki M, et al. Am J Clin Nutr 2006
• Liver problems
• Fat absorption problems

The body’s K1 =>K2 conversion ratio is said to be about 10:1 and is enhanced by the presence of fat

Although animals can convert K1K2 , evidence suggests that the human diet needs to contain preformed K2 for optimal health:

• Gut bacteria can convert K1 into K2 (MK-7 homolog) but we seem unable to affectively absorb more than a small amount of the K2 they produce – since most of the vitamin K2 produced in the intestine are embedded within bacterial membranes.  Unden, G. and J. Bongaerts (1997). “Alternative respiratory pathways of Escherichia coli: energetics and transcriptional regulation in response to electron acceptors.” Biochim Biophys Acta 1320(3): 217-234.
• Dietary K1 is preferentially used by the liver to make blood clotting factors.    Whilst K2 is preferentially used for other tissues, and much more than just bones
• Intake of K2 is inversely associated with heart disease in humans while intake of K1 is not. Geleijnse JM, Vermeer C, Grobbee DE, Schurgers LJ, Knapen MHJ, van der Meer IM, Hofman A and Witteman JCM. “Dietary intake of menaquinone is associated with a reduced risk of coronary heart disease: The Rotterdam Study” November 2004; J Nutr 134:3100-3105
• Vitamin K2 is at least three times more effective thanvitamin K1 at activating proteins related to skeletal metabolism – K2(MK-7) increased the percentage of OSTEOCALCIN in humans three times more powerfully than did synthetic vitamin K1.  Schurgers LJ, Vermeer C., 2000. Determination of Phylloquinone and Menaquinones in Food. Haemostasis. 2000; 30: 298-307
• The study showing vitamin K2′s dramatic role in treating prostate cancer, revealed that vitamin K1 had no effect. Study by European Prospective Investigation into Cancer and Nutrition (EPIC), Heidelburg, German

K Absorption

K2 is better absorbed than K1 and remains active much longer

• K1 is cleared by the liver within 8 hours, but measurable levels of K2 have been detected 72 hours after ingestion. Schurgers LJ, Teunissen KJ 2007
• K2 absorption from natto (fermented soy) is almost 100%, compared to K1 absorption rate from 200-400g green vegetables, which ranges from 5-15% depending on how much fat is present.   interestingly, absorption rate is higher for smaller portions (~5oz spinach is 17%, ~2oz serving is 28%) Gijsbers et al., 1996; Garber et al, 1999

Phylloquinones present in green leafy vegetables are tightly bound to the thylakoid membranes in plant chloroplasts, and are not well solubilized and absorbed without the concomitant intake of fat, which stimulates bile secretion. Gijsbers et al, 1996; Schurgers and Vermeer, 2000; Schurgers, 2002; Vermeer et al., 2004

K2 is carried in the lymph in mixed micelles composed of bile salts, and subsequently released into the circulation.

• Higher /more stable plasma levels of vitamin K were reached with supplements containingK2 (MK-7) compared to those achieved with vitamin K1. Vermeer, 2003
• The length of the side chain of the menaquinone form affects bioavailability.   Medium-length side chains (e.g., MK-7) are better absorbed compared to those with short (MK-4) or long (e.g., MK-8 and MK-9) side chains. Schurgers and Vermeer, 2000; Schurgers, 2002.
• Humans appear to have a finite ability to absorb vitamin K1 from vegetables, which dietary source may not be enough to support skeletal needs.   US mean intake of K1 is <150 mcg/day and blood levels increase with dietary intake up to 200 mcg/day, after which they plateau. The Dutch have a mean intake of 250 mcg/day, but their K1 plasma levels have no relationship to dietary intake, (McKeown et al, 2002 suggesting that humans are unable to absorb much more than 200 mcg of K1 /day from vegetables. As mentioned above, our absorption of K1 declines as the amount we consume increasesstrengthening the interpretation that we might only be able to absorb ~200 mcg/day. Study subjects required an oral dose of 1000mcg of a highly absorbable pharmacological preparation of vitamin K1 to maximize the activation of proteins important to bone metabolism. (Binkley et al, 2002)If we can only absorb one-fifth of this amount from vegetables, we cannot support our skeletal system with vitamin K1 regardless of how efficiently we may be able to convert it to vitamin K2.

Absorption of vitamin K (as other fat-soluble vitamins E.g. A, D and E) depends on healthy liver, gallbladder and digestive function.   Deficiency is more likely in people with digestive problems such as pancreatic disease, celiac disease, irritable bowel syndrome (IBS), ulcerative colitis, Crohn’s disease or those who have had intestinal bypass surgery.

Binkley NC, Grueger DC, Kawahara TN, Engelke JA, Chappell RJ, Suttie JW. 2002. A high phylloquinone intake is required to achieve maximal osteocalcin gamma-carboxylation. Am J Clin Nutr. 2002; 76: 1055-60.

Garber AK, Binkley NC, Krueger DC, Suttie JW. 1999. Comparison of Phylloquinone Bioavailability from Food Sources or a Supplement in Human Subjects. J Nutr. 1999; 129: 1201-1203.

Gijsbers BLMG, Jie K-SG, Vermeer C. 1996. Effect of food composition on vitamin K absorption in human volunteers. Br J Nutr. 1996; 76: 223-229.

McKeown NM, Jacques PF, Gundberg CM, Peterson JW, Tucker KL, Kiel KP, Wilson PWF, Booth SL.2002. Dietary and nondietary determinants of vitamin K biochemical measures in men and women.J Nutr. 2002; 132(6): 1329-1334.

Schurgers LJ, Vermeer C., 2000. Determination of Phylloquinone and Menaquinones in Food. Haemostasis. 2000; 30: 298-307

Schurgers LJ, Teunissen KJF, Hamulyak K, Knapen MHJ, Hogne V, Vermeer C.2007. Vitamin K-containing dietary supplements: comparison of synthetic vitamin K1 and natto-derived menaquinone-7. Blood. 2006; [Epub ahead of print].

Vermeer, C. 2003. Pharmacokinetics of vitamin K2 after ingestion of natto food and natto capsules. (Natto-1 Study). VitaK/University of Maastricht. Research Project, July 25, 2003.

Vermeer, C., Shearer, M.J., Zittermann, A., Bolton-Smith, C., Szulc, P., Hodges, S., Walter, P., Rambeck, W., Stocklin, E., Weber, P. 2004. Beyond deficiency: Potential benefits of increased intakes of vitamin K for bone and vascular health. Eur. J. Nutr. 43(6), 325-335.

Is K stored in the body?

• Although vitamin K is a fat-soluble vitamin, the body stores very little of it and its stores are rapidly depleted without regular dietary intake
• Unlike the other fat-soluble nutrients (vitamins A, D, and E), vitamin K is NOT significantly stored in the body.   Beneficial bacteria(called probiotics) produce vitamin K2, but absorption of this source is poor (especially in those with digestive problems) and most people are short of these beneficial bacteria. Vitamin K must be provided daily to avoid a K- deficiency, which can develop in as few as 7 days on a vitamin K-deficient diet. Israels LG, Israels ED, et al, The riddle of vitamin K1 deficit in the newborn.Semin Perinatol. 1997 Feb;21(1):90-6.)
• Vitamin K cycle conserves K.   Allowing a small amount of vitamin K to be recycled many times in the gamma-carboxylation of proteins. (see Health Benefits of Vitamin K). Warfarin / Coumadin blocks this recycling, effectively creating a functional K-deficiency