The relationship between vitamin D and bone, heart health and calcium metabolism is particularly interesting because of the simultaneous involvement of other nutrients, notably vitamin K. These two vitamins work in tandem to help prevent serious disease.
Vitamin D plays a role in many diseases other than bone and in this it is frequently assisted by vitamin K. Vitamin D receptors have been discovered in a variety of tissues other than bone including brain, breast, prostate and immune cells. Research has suggested that higher vitamin D levels in association with vitamin K may provide protection against cardiovascular disease, metabolic syndrome, diabetes, osteoporosis, autoimmune diseases and cancers of the breast, colon and prostate. Thus with the latest knowledge of vitamin D we can now use the vitamin for a wider range of preventative and therapeutic applications to maintain and improve health.
VITAMIN D RECOMMENDED REQUIREMENTS
Vitamin D deficiency is far more common than previously assumed and needs serious consideration because the health consequences of such a deficiency reach beyond the role that the vitamin plays in calcium (mineral) absorption. Vitamin D deficiency may be caused by decreased exposure to the sun (for example in the northern latitudes) and impaired absorption mechanisms. The amount of the vitamin formed normally in the body under the influence of the sun’s ultraviolet rays is significant: a single 20-minute, full body exposure to summer sun will trigger the formation of 500 mcg of vitamin D in the circulation of most people within 48 hours. Most official bodies in various countries report a lower limit. Many authorities at the present time believe that the daily physiological requirement for adult humans may be as high as 125 mcg, which is considerably lower than the amount endogenously produced with full body sun exposure.3
VITAMINS D AND K PREVENT CANCER AND HEART DISEASE
The role of vitamin D in the prevention of cancer and heart disease is of particular interest.
Scientists at the University of California wrote a review report of 63 published papers on the relationship between cancer incidence and vitamin D nutritional status. The review revealed that cancer rates can be drastically reduced by raising blood levels of the vitamin beyond dietary levels by means of supplementation.
In order for calcium (and some other minerals) to be absorbed, vitamin D is required. After absorption and when calcium appears in the blood, the fate of calcium is determined by the presence or absence of vitamin K. In this manner vitamin K may prevent both heart disease and osteoporosis.
Arteriosclerosis occurs when the middle layer of the arteries is severely calcified and hardened and the arteries are unable to expand and contract during the heartbeat, thereby increasing the chances of a heart attack.1 The incidence of sudden death is seven times higher in patients with calcified arteries.
Scientists in Japan first showed that the calcification of arteries can be drastically reduced by the administration of vitamin K, which reduced the level of calcium in the arteries by up to 17 times. The fate of calcium in the blood is thus determined by the absence or presence of vitamin K and the extent to which calcium goes to the arteries instead of the bones, is determined by the vitamin K status of the patient.2 In the presence of adequate levels of the vitamin, calcium follows its normal route to the bones preventing inter alia osteoporosis.
VITAMINS D AND K PREVENT OSTEOPOROSIS
Vitamins D and K are both necessary for bone maintenance, but several additional factors such as parathyroid hormone (regulates the amount of calcium in the body), oestrogen and calcitonin (a hormone necessary for the metabolism of calcium) are required. In normal patients these are usually not in short supply, at least to such an extent that bone maintenance may be compromised. When all of these factors are present in adequate amounts, the skeleton will be renewed every 8 to 10 years, but in old age this process becomes slower. Vitamins D and K appear to be of special significance in the elderly in whom osteoporosis and bone fractures often cause serious problems.
In one major study on 72 000 nurses (known as the Nurses’ Study) lasting 10 years, it was concluded that the nurses who got the most vitamin K were about 30% less likely to suffer from hip fractures. Those who ate lettuce every day, reduced their hip fracture risk by 50% compared to those who only ate lettuce once a week. Lettuce is a significant dietary source of vitamin K. The study showed that the effect of vitamin K on reducing osteoporotic fractures was better than that of oestrogen, which did not significantly protect the participants’ bone density. Interestingly enough, nor did vitamin D alone. In fact, women who took high doses of vitamin D alone, but who had a low intake of vitamin K, doubled their risk of hip fracture.
Other studies showed that vitamin K has a significant effect on bone loss in a post- menopausal population. This was confirmed by an independent study in the Netherlands that showed that 1 mg of vitamin K per day for a period of 14 days increased the level of carboxylated glutamic acid by 70 to 80% in post-menopausal women to the same level as that in premenopausal women.
Bone density and mortality risk Osteoporosis may be a sign of other serious health problems. The Study of Osteoporotic Fractures4 revealed that bone density is an unexpectedly strong predictor of death. The study showed that every standard deviation away from normal bone density was associated with 20% increased risk of death in women aged 65 and older. For example, while 46 deaths occurred in a particular segment of the study in people with the highest bone density, 78 deaths occurred in the group with the lowest bone density. Quite unexpectedly, in this group women with osteoporosis did not die in the first place from broken bones and the associated complications. Falling accounted for only 3% of deaths in this osteoporosis study. The majority of deaths in this group was due to heart attacks, cancer and stroke. It was concluded that calcium, which was supposed to be in the bones, was in fact relocated to the arteries as discussed above. The study found that women who had one or more back fractures, had a 23% increased risk of dying. Severe hump back increased the risk of dying from a lung related disorder, such as a blood clot, by as much as 2.6 times.
VITAMIN K AND STROKE
Studies on the underlying causes of stroke have in the past often centred on dietary salt as a regulator of blood pressure. However, a found that calcium concentration in the arterial wall may be involved in much the same way as previously discussed in the heart vessels. Vitamin K supplements prevented the thickening of arteries in in-vivo tests.
A recent report from the Dietary Approaches to Stop Hypertension (DASH) study indicates that it makes no difference to your blood pressure how much salt you eat or how much you weigh. What does make a difference is whether you eat fruit and vegetables which once again focuses attention on the calcium regulating vitamin K of which dietary fruits and vegetables are an important dietary source. Although more specific studies are required, these studies indicate that vitamin K may be an important factor in determining your blood pressure and therefore that it may reduce the incidence of stroke and bring order to the multitude of confusing and conflicting studies which have attempted to define the true causes of hypertension and stroke.
VITAMIN K: SOURCES AND RECOMMENDED REQUIREMENTS
Green leafy vegetables supply about 40 to 50% of vitamin K. Vegetable oils are the next highest source. Hydrogenated oils, such as margarine, contain an unnatural form of the vitamin which antagonises the action of natural vitamin K.
There are three different forms of vitamin K: K1 from plants, K2 from bacteria and K3 which is synthetic and less desirable. K2 appears to be the
preferred form because it specifically keeps calcium out of the arteries. The body converts K1 into K2. Vitamin K in the form of K1 and K2 is not toxic, even in high doses and unlike other fat soluble vitamins it does not accumulate in the body. High amounts of the vitamin will also not cause the blood to over-coagulate since once the co- agulation proteins have been saturated with the vitamin, further increases of vitamin K will have no effect.6
Up to 45 mg a day have been used in osteoporosis studies in Japan. No final recommendations of dosage level are available since individual requirements are determined by diet, age and the presence of stressors. Generally, 10 mg per day are recommended.
THE MECHANISM OF VITAMIN K
The way in which vitamin K ensures that calcium goes to the bones instead of the arteries is an interesting one. The process centers around an amino acid called gamma carboxyglutamic acid. The glutamic acid molecule acquires additional ‘claws’ by means of which it can bind calcium and carry it to the bones. The glutamic acid molecules occur in nature as part of calcium and carrying proteins. Vitamin K is necessary for these proteins to function as indicated. When there is a deficiency of vitamin K, calcium leaves the bones and teeth and drifts towards the arteries, thereby contributing to the risk of heart attacks and osteoporosis.
VITAMIN K STRESSORS
Here are some factors in the modern diet that may suppress the bioavailability of vitamin K:
- Cholesterol-reducing drugs and low fat diets or anything that interferes with fat me- tabolism. Our past misplaced conception on the possible link between heart disease and blood cholesterol is mainly responsible for these.
- Antibiotics: vitamin K producing intestinal bacteria, which are an important source of vitamin K2, are destroyed by antibiotics.
- Unwarranted dietary restrictions, slimming diets, low fat diets etc. all contribute to reducing the bioavailability of vitamin K. Remember it is the oil in your green salad dressing that enables the vitamin K in your green salad to be absorbed.
Note: Patients who take blood thinners such as Cuomadin, should not take vitamin K without consulting their doctor.
- Mönckeberg JG. Über die reine Mediaverkalkung der Extremitätenarterien und ihr Verhalten zur Arteriosklerose. Virchows Arch Pathol Anat. 1903; (171):141-67.
- Ronden JE. Modulation of arterial thrombosis tendency in rats by vitamin K and its side chains. Atherosclerosis. 1997 Jul 11; 132(1):61-7.
- Vieth R. Vitamin D supplementation,
- 25-hydroxyvitamin D concentrations, and safety. Am J Clin Nutr. 1999; (69): 842. And: Heaney RP. Vitamins, minerals, and phytochemicals. Am J Clin Nutr. 2003; (77): 204-10.
- Kado DM. et al. Vertebral fractures and mortality in older women: a prospective study. Arch. Intern. Med. 1999; (159):1215-20.
- Svetkey LP., et al. Effects of dietary patterns on blood pressure: subgroup analysis of the Dietary Approaches to Stop Hypertension (DASH) randomized clinical trial. Arch Int Med 1999; (159): 285.
- Life Extension Feb 2000, pg. 38.