Joseph Mercola, D.O.
Accumulating evidence suggests that atherosclerotic calcification
shares features with bone calcification. Vascular calcification,
or hardening of the arteries, is common and clinically significant
in 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 awareness
that vascular calcification is a biologically regulated phenomenon.
In addition to being involved in the formation of osteocalcin,
vitamin K is known to be involved in the formation of matrix
Gla-protein (MGP). Osteocalcin is a protein produced by the
osteoblasts, and is utilized within the bone as an integral
part of the process of its formation. However, osteocalcin
must be carboxylated before it can be effective in bone formation.
Vitamin K functions as a cofactor for the enzyme that catalyzes
the carboxylation of osteocalcin.
MGP is synthesized in a vitamin K-dependent way in smooth
muscle cells of the healthy vessel wall.
A recently described function of MGP is as a powerful inhibitor
of calcification of arteries and cartilage. It appears that
optimal vitamin K levels are needed to produce proper amounts
of MGP to prevent arterial calcification. MGP deficient
mice develop extensive vascular calcification with replacement
of the vascular media by progressively calcifying cartilage.
Types and Source of Vitamin K
Vitamin K1, is also called phylloquinone or menaquinone 4.
It is typically found in dark green leafy vegetables. Vitamin
K2 has the chemical name menaquinone 7 and is synthesized
by intestinal bacteria, and absorbed from the distal small
bowel. Antibiotics have been shown to reduce vitamin K2 from
Fermented foods typically have the highest concentration
of vitamin K found in the human diet and can provide several
milligrams of vitamin K2 on a daily basis. This level far
exceeds the amount found in dark green vegetables.
Natto is a fermented soy product that has been a staple food
of eastern Japan for over 1,000 years. Many find it unpalatable
due to its slimy texture, but it is far better absorbed than
vitamin K from vegetables. Circulating vitamin K2 concentrations
after the consumption of natto have been shown to be about
10 times higher than those of vitamin K1 after eating spinach.
Japanese researchers found a statistically significant inverse
correlation between the incidence of hip fractures in women
and natto consumption. In other words, the more natto
consumed, the lower the incidence of hip fracture. Feeding
ovariectomized rats natto has also been shown to have a preventive
effect on bone loss.
Although fermented food products provide the highest source
of vitamin K, even relatively low vitamin-K-containing vegetables
like lettuce, consumed one or more times per day, have produced
a 45 percent lower risk of hip fracture as compared to women
who consumed lettuce once or fewer times per week.20
Dosing and Toxicity of Vitamin K
Considering that the undercarboxylation of MGP is a risk
factor for vascular calcification, it would seem the present
Recommended Dietary Allowance (RDA) values for vitamin K are
too low to ensure full carboxylation of MGP to decrease atherosclerosis.
Other compelling evidence for an increased requirement for
vitamin K is that nearly half of newborns were shown to have
low vitamin K levels by the accurate undercoboxylated prothrombin
vitamin K assay, despite their mothers consuming dietary levels
equal to the RDA of 1 mcg/kg.
There are no comparative studies on different dosing schedules
of vitamin K, but it is likely that a dose of 1 to 5 mg daily
(1000-5000 mcg) would approximate the levels seen in Japanese
women who regularly consumed natto, fermented foods or dark
Unlike vitamin D, which is toxic in large doses, vitamin
K1 (phylloquinone) is not toxic at 500 times the RDA. However,
synthetic vitamin K3 (menadione) toxicity has occurred in
infants given vitamin K3 by injection.
Vitamin K taken without fat is poorly absorbed. It appears
that at least an ounce of fat is needed to optimize absorption.
Supplemental vitamin K1 appears to be much more available
than vitamin K1 in a food source. Absorption of vitamin K1
was found to be about six times greater when it was ingested
in the pure form as a tablet than when it was present in a
food matrix, such as fresh spinach.
The best sources of vitamin K are leafy green vegetables.
Eggs have some as well. Below are a few examples of the vitamin
K content of some good sources.
If for whatever reason you are unable to obtain enough vitamin
K then you might want to consider the relatively inexpensive
form of vitamin K that we are
now carrying in our store.
This form has 500 mcg per drop, so 6 drops would give you
3000 mcg. You would have to eat over one pound of collard
greens to get the equivalent amount of vitamin K. Clearly
the collard greens or spinach would be better for you and
would provide you with additional benefits, but if you already
have heart disease a little extra vitamin K would seem a simple
bit of insurance to make sure that your blood vessels don't
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 Dhore CR, Cleutjens JP, Lutgens E, et. al. Differential
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