Vitamin K: The Misunderstood Vitamin
Contributed by LifeExtension Foundation
Ask doctors what vitamin K does, and most will tell you it is involved in the clotting process … period!
As early as 1984, however, scientists reported that patients who suffered fractures caused by osteoporosis had vitamin K levels that were 70% lower than age-matched controls. Later studies also confirmed diminished bone mineral density in the presence of low-serum vitamin K levels.
Other statistics showed that women with the lowest blood levels of vitamin K had a 65% greater risk of suffering a hip fracture compared to those with the highest vitamin K levels.
Another unfortunate result of a vitamin Kdeficient state is that the calcium intended to form strong bones is instead deposited onto the arterial wall in enormous amounts, thereby contributing to the process of atherosclerosis. This explains why so many aging individuals suffer from hardened calcified arteries, while having brittle bones that are markedly depleted of calcium.
Doctors in a huge European human clinical trial evaluated the vitamin K intake of 4,807 subjects over a 7- to 10-year period. After adjusting for other risk factors, coronary heart disease risk was reduced with increased intake of vitamin K2. Those who consumed the most vitamin K2 had a 57% reduction in cardiac disease compared to those who consumed the least.
What has scientists most excited is that vitamin K2 is proving itself to be superior to K1.
Obtained in the diet primarily from dark leafy vegetables (lettuce, spinach, and broccoli), vitamin K1 is tightly bound to the chlorophyll in green plants, meaning that those with compromised digestive tracts are unable to benefit as well from eating K1-rich plants. Interestingly, K1, a fat-soluble vitamin, is better absorbed as a supplement, provided it is taken with meals containing fat.
Vitamin K2 is found in much smaller quantities in the diet, with the highest dietary levels in fermented soy natto. Human studies show that K2 is absorbed up to 10 times more than K1. Japanese people consume large quantities of natto, which may explain their lower rates of heart disease and osteoporosis compared to Western populations.
K2 also remains biologically active in the body far longer than K1. For instance, K1 is cleared by the liver within 8 hours, whereas measurable levels of K2 have been detected 72 hours after ingestion. This means vitamin K2 is available to facilitate transport of calcium into the bone and protect the arterial wall much longer than K1.
VITAMIN K IMPEDES ATHEROSCLEROSIS
In a study of 188 post-menopausal women, a group known to be at high risk for rapid blood vessel structure decay, a supplement containing 1 mg of vitamin K1 or a placebo was administered over a 3-year period. In the vitamin K group, age-related arterial (blood vessel) stiffening was completely abolished, whereas the placebo group experienced a 13% decline of arterial elasticity during the study period.
HOW VITAMIN K PROTECTS ARTERIES FROM CALCIFICATION
Vitamin K controls calcium-regulating proteins, such as calcitonin, which have been shown to prevent calcification in the blood vessels. Activation of these proteins depends on the availability of vitamin K. When there is not enough vitamin K to turn these proteins on, calcium deposits into atherosclerotic plaque, thus increasing cardiovascular disease risk and leading to the condition known as "hardening of the arteries." This helps explain why patients taking vitamin-K depleting, anti-coagulant drugs (like Coumadin®) suffer from accelerated atherosclerosis.
In most, vitamin K from dietary sources fills the need for proper coagulation. As people age, however, a sub-clinical vitamin K deficiency can pose severe risks to the vascular system.
VITAMIN K2 INTAKE LINKED TO REDUCED ARTERIAL DISEASE
In the most significant human study to date, a large group with no history of heart disease was followed from 1990 until year 2000. The incidence of coronary artery disease, all-cause mortality, and severe aortic atherosclerosis were studied in relationship to the amount of vitamin K1 and/or K2 ingested over the study period. Those who consumed the most vitamin K2 showed significant disease reductions, compared to those who ingested the least K2.
In this study, intake of vitamin K1 from dietary sources was not related to these risk reductions, probably due to the poor bioavailability of K1 from plant foods. The scientists who conducted this study concluded that adequate intake of vitamin K2 could contribute to the prevention of coronary artery heart disease, specifically at a 26% reduction in death by any cause, a 57% reduction in coronary artery disease, and a 68% reduction in severe aortic atherosclerosis.
VITAMIN K AND BONE FRACTURE PREVENTION
A systemic review was made of all randomized controlled trials that gave adults either vitamin K1 or K2 supplements for at least six months. A total of 13 trials were identified with data on bone loss and seven trials that reported fracture incidences. All but one of these human trials showed supplemental vitamin K1 or K2 reduced bone mass loss. Vitamin K2, in particular, was associated with increased bone mineral density. In all seven trials that evaluated fracture risk, vitamin K2 proved most effective, reducing the risk of vertebral fractures by 60%, hip fractures by 77%, and an astounding reduction for all non-vertebral fractures of 81%.
The past 15 years of research has shown that vitamin K, particularly the K2 form, is far more than a necessary element of blood coagulation. Scientists have found that vitamin K plays a crucial role in arterial and bone health. Recent studies indicate that vitamin K intake that is substantially above the government's recommended reference range can slow bone loss, reduce arterial stiffening, prevent heart attack, and reduce death rates in adult human populations.