ByJoseph Mercola, D.O.
Accumulating evidence suggests that atherosclerotic calcificationshares features with bone calcification. Vascular calcification,or hardening of the arteries, is common and clinically significantin atherosclerosis (coronary artery disease) and heart failure.It was long believed to be an end-stage process of "passive"mineral precipitation. However, there is now a growing awarenessthat vascular calcification is a biologically regulated phenomenon.1
In addition to being involved in the formation of osteocalcin,vitamin K is known to be involved in the formation of matrixGla-protein (MGP). Osteocalcin is a protein produced by theosteoblasts, and is utilized within the bone as an integralpart of the process of its formation. However, osteocalcinmust be carboxylated before it can be effective in bone formation.Vitamin K functions as a cofactor for the enzyme that catalyzesthe carboxylation of osteocalcin.
MGP is synthesized in a vitamin K-dependent way in smoothmuscle cells of the healthy vessel wall.2
A recently described function of MGP is as a powerful inhibitorof calcification of arteries and cartilage. It appears thatoptimal vitamin K levels are needed to produce proper amountsof MGP to prevent arterial calcification.3 MGP deficientmice develop extensive vascular calcification with replacementof the vascular media by progressively calcifying cartilage.4
Types and Source of Vitamin K
Vitamin K1, is also called phylloquinone or menaquinone 4.It is typically found in dark green leafy vegetables. VitaminK2 has the chemical name menaquinone 7 and is synthesizedby intestinal bacteria, and absorbed from the distal smallbowel. Antibiotics have been shown to reduce vitamin K2 fromthis source.5
Fermented foods typically have the highest concentrationof vitamin K found in the human diet and can provide severalmilligrams of vitamin K2 on a daily basis. This level farexceeds the amount found in dark green vegetables.
Natto is a fermented soy product that has been a staple foodof eastern Japan for over 1,000 years. Many find it unpalatabledue to its slimy texture, but it is far better absorbed thanvitamin K from vegetables. Circulating vitamin K2 concentrationsafter the consumption of natto have been shown to be about10 times higher than those of vitamin K1 after eating spinach.6
Japanese researchers found a statistically significant inversecorrelation between the incidence of hip fractures in womenand natto consumption.7 In other words, the more nattoconsumed, the lower the incidence of hip fracture. Feedingovariectomized rats natto has also been shown to have a preventiveeffect on bone loss.8
Although fermented food products provide the highest sourceof vitamin K, even relatively low vitamin-K-containing vegetableslike lettuce, consumed one or more times per day, have produceda 45 percent lower risk of hip fracture as compared to womenwho consumed lettuce once or fewer times per week.20
Dosing and Toxicity of Vitamin K
Considering that the undercarboxylation of MGP is a riskfactor for vascular calcification, it would seem the presentRecommended Dietary Allowance (RDA) values for vitamin K aretoo low to ensure full carboxylation of MGP to decrease atherosclerosis.9
Other compelling evidence for an increased requirement forvitamin K is that nearly half of newborns were shown to havelow vitamin K levels by the accurate undercoboxylated prothrombinvitamin K assay, despite their mothers consuming dietary levelsequal to the RDA of 1 mcg/kg.10
There are no comparative studies on different dosing schedulesof vitamin K, but it is likely that a dose of 1 to 5 mg daily(1000-5000 mcg) would approximate the levels seen in Japanesewomen who regularly consumed natto, fermented foods or darkgreen vegetables.
Unlike vitamin D, which is toxic in large doses, vitaminK1 (phylloquinone) is not toxic at 500 times the RDA. However,synthetic vitamin K3 (menadione) toxicity has occurred ininfants given vitamin K3 by injection.
Vitamin K taken without fat is poorly absorbed. It appearsthat at least an ounce of fat is needed to optimize absorption.11Supplemental vitamin K1 appears to be much more availablethan vitamin K1 in a food source. Absorption of vitamin K1was found to be about six times greater when it was ingestedin the pure form as a tablet than when it was present in afood matrix, such as fresh spinach.12
The best sources of vitamin K are leafy green vegetables.Eggs have some as well. Below are a few examples of the vitaminK content of some good sources.
|Food||Vitamin K |
If for whatever reason you are unable to obtain enough vitaminK then you might want to consider the relatively inexpensiveform of vitamin K that we arenow carrying in our store.
This form has 500 mcg per drop, so 6 drops would give you3000 mcg. You would have to eat over one pound of collardgreens to get the equivalent amount of vitamin K. Clearlythe collard greens or spinach would be better for you andwould provide you with additional benefits, but if you alreadyhave heart disease a little extra vitamin K would seem a simplebit of insurance to make sure that your blood vessels don'tharden.
1 Tintut Y, Demer LL. Recent advances in multifactorialregulation of vascular calcification. Curr Opin Lipidol.2001 Oct;12(5):555-60
2 Dhore CR, Cleutjens JP, Lutgens E, et. al. Differentialexpression of bone matrix regulatory proteins in human atheroscleroticplaques. Arterioscler Thromb Vasc Biol. 2001 Dec;21(12):1998-2003
3 Shearer Role of vitamin K and Gla proteins in thepathophysiology of osteoporosis and vascular calcification.MJ.Curr Opin Clin Nutr Metab Care 2000 Nov;3(6):433-8
4 Bostrom K. Insights into the mechanism of vascularcalcification. Am J Cardiol. 2001 Jul 19;88(2-A):20E-22E
5 Conly J, Stein K. Reduction of vitamin K2 concentrationsin human liver associated with the use of broad spectrumantimicrobials. Clin Invest Med 1994 Dec;17(6):531-9
6 Schurgers LJ, Vermeer C. Determination of phylloquinoneand menaquinones in food. Effect of food matrix on circulatingvitamin K concentrations. Haemostasis. 2000 Nov-Dec;30(6):298-307
7 Kaneki M, Hedges SJ, Hosoi T, et. al. Japanese fermentedsoybean food as the major determinant of the large geographicdifference in circulating levels of vitamin K2: possibleimplications for hip-fracture risk. Nutrition 2001 Apr;17(4):315-21
8 Yamaguchi M, Ma Z J. Inhibitory effect of menaquinone-7(vitamin K2) on osteoclast-like cell formation and osteoclasticbone resorption in rat bone tissues in vitro. Mol Cell Biochem2001 Dec;228(1-2):39-47
9 Schurgers LJ, Dissel PE, Spronk HM, et. al.Role ofvitamin K and vitamin K-dependent proteins in vascular calcification.Z Kardiol. 2001;90 Suppl 3:57-63.
10 Greer FR. Are breast-fed infants vitamin K deficient?Adv Exp Med Biol. 2001;501:391-5
11 Uematsu T., Nagashima S., Masayuki N., et. al. Effectof dietary fat content on oral bioavailability of menatetranonein humans. J. Pharmacol. Sci. 1996;85:1012-1016
12 Garber AK, Binkley NC, Krueger DC, et. al. Comparisonof phylloquinone bioavailability from food sources or asupplement in human subjects. J Nutr. 1999 Jun;129(6):1201-3