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Currently, long-term space travel is not possible for humans because the lack of gravity causes rapid resorption of bone along with suppression of new bone formation. This effect can be mimicked by suspending the tails of rats so that they are not subject to the pull of gravity. Another group of Japanese researchers used this animal model to examine the effects of vitamin K on bone mass. When vitamin K was given orally in high doses-22 mg/kg body weight-the structure of the bones in the rats' tails was maintained at almost normal levels.
Ovarian hormone production has a strong preservative effect on bone mass, and postmenopausal women have the greatest risk of ending up with osteoporosis. Following ovariectomy (removal of the ovaries) in rats, vitamin K was administered. The K supplement attenuated the decline in bone mineral density typically seen after ovariectomy.[20,21] In another study, researchers found that postmenopausal women given one milligram of vitamin K daily for two weeks showed an increase of 70% to 80% in carboxylated Gla-a good sign that calcium is going where it should.
One of the best ways to prevent osteoporosis in old age is to maximize bone density during youth. This can be accomplished with exercise and adequate nutrition during the height of a child's growth phase, and supplemental vitamin K may prove a valuable adjunct to these bone-building efforts. To determine whether nutrient supplementation in youth can increase peak bone mineral density, 168 three-month-old female rats were divided into five groups. One got a control diet; the other groups received either vitamin D, vitamin K, calcium, or vitamins D and K plus calcium. In all four groups with added nutrients, peak bone mineral density (BMD) was higher than in the control group. The greatest improvements in increasing bone density in the short-term was seen in the calcium-only group, but the smallest decreases in bone mineral density (BMD) over the course of the study was seen in the group that got the combination of nutrients. In other words, all three nutrients (calcium, vitamin D and vitamin K) taken together protected against bone loss better than any of them by themselves.
Bone loss is a common complication of cirrhosis of the liver. When patients were given vitamin K, carboxylation of osteocalcin-one of the Gla proteins-significantly improved.
Other benefits of vitamin K
The benefits of vitamin K don't stop at osteoporosis and heart disease prevention. Further research has demonstrated that this nutrient also relieves inflammation. With age, concentrations in the body of a substance called interleukin-6 (IL-6) increase. IL-6 is a biochemical messenger called a cytokine. It accelerates inflammation when produced out of balance with other cytokines. People who suffer from arthritis and Alzheimer's disease have high IL-6 concentrations, as do blood vessels affected by atherosclerosis. A study performed at the National Research Institute in Italy revealed that subjects with the highest levels of IL-6 were nearly twice as likely to end up with a mobility-related disability.
Diabetics may be poised to benefit from vitamin K supplements more than any other segment of the population. Type II diabetics are more subject to all types of arteriosclerosis; the abundance of sugars and insulin in their systems accelerate the aging process that naturally predisposes people to pathological calcium deposition. The fact that the pancreas contains the second highest concentration of vitamin K in the body hints at its role in blood sugar regulation. Japanese researchers have found that when vitamin K deficiency is induced in rats, the clearance of blood glucose is impaired and insulin release increases-in other words, the rats developed the symptoms of early type II diabetes (i.e. hyperinsulinemia).
Vitamin K's benefits may also be linked to its antioxidant activity. Some research has indicated that vitamin K has free radical-scavenging power comparable to that of vitamin E and coenzyme CoQ10.[27,28] The livers of animals subjected to oxidative stress gained complete protection when given vitamin K, and vitamin K has been found to be 80% as effective as vitamin E at preventing the oxidation of polyunsaturated linoleic acid.
If you are using ginger, garlic, ginkgo or aspirin to keep your blood thin and prevent clotting, don't worry that taking supplemental vitamin K will counteract this. While vitamin K does participate in blood coagulation, it prevents platelet aggregation-a process of blood cell clumping that is spurred by increases in oxidative stress. Keep in mind that K also plays a role in activating anti-clotting proteins, even while participating in the blood clotting cascade.
Supplementing vitamin K may also help to prevent Alzheimer's disease. Those with the E4 form of the lipoprotein apoE-about 25% of the population-are known to have increased risk of developing this dreaded disorder. What many don't know is that people who carry the apoE4 gene have been found to have low vitamin K levels. The calcification and development of lesions in blood vessels that feed brain tissues is believed to be one aspect of Alzheimer's development, and further research may reveal an important role for high-dose vitamin K in its prevention.
Vitamin K supplementation guidelines
Generally, 10 mg per day is a good dose for any person interested in optimal health and longevity. Those suffering from osteoporosis may consider taking up to 40 mg a day. Those taking higher doses may wish to have their vitamin K levels evaluated. Ask your doctor or nutritionist to administer the osteocalcin test. This test measures levels of carboxylated osteocalcin, yielding an excellent picture of vitamin K status.
1. Matschiner JT, et al, Mechanism of the effect of retinoic acid and squalene on vitamin K deficiency in the rat. J Nutr 1967;91:303-6.
4. Witteman JC, et al, Aortic calcified plaques and cardiovascular disease (the Framingham Study). Am J Cardiol 1990;66:1060-4.