Large epidemiological studies have demonstrated a relationship between vitamin K and age-related bone loss (osteoporosis). The Nurses' Health Study followed more than 72,000 women for 10 years. In an analysis of this group, women with the lowest vitamin K intakes had a 30% higher risk of hip fracture than women with the highest vitamin K intakes (11). A study in over 800 elderly men and women, followed in the Framingham Heart Study for seven years, found that men and women with high dietary vitamin K intakes had a 65% lower risk of hip fracture. However, the investigators found no association between dietary vitamin K intake and bone mineral density (BMD) (12).
Other studies have not observed a relationship between dietary vitamin K intake and measures of bone strength, BMD or fracture incidence (13). However, vitamin K intake was lower in the investigated group and the study design was not ideal as 50% of the participants received hormone replacement therapy influencing BMD. Long-term clinical trials of vitamin K1 (phylloquinone) supplementation at doses attainable by dietary intake (200 to1,000 micrograms (mcg) per day) have reported mixed results with respect to effects on bone mineral density (14, 15, 16). It is not quite clear, if phylloquinone supplementation at these levels has potential bone health benefits in older individuals, especially in those subjects, who are also taking vitamin D and calcium supplements (16). However, promising evidence emerges from some more recent cross-sectional and case-control studies where associations between higher phylloquinone intakes and lower incidence of hip fracture have been reported (42). Other studies indicated that higher circulating phylloquinone levels were associated with lower fracture risk (43).
Thus, final evidence of a relationship between vitamin K nutritional status and bone health in adults needs further exploring and potential synergistic effects with vitamin D and calcium need to be evaluated. Further investigations with well-designed studies are required to determine the physiological function of vitamin K-dependent proteins in bone and the mechanisms by which vitamin K affects bone health and osteoporotic fracture risk (17).
One of the hallmarks of cardiovascular disease is the buildup of fatty material (lipids), cholesterol and calcium called ‘atherosclerotic plaques’ within blood vessel walls. As the condition progresses, incorporation of calcium (‘calcification’) into atherosclerotic plaques occurs, resulting in decreased elasticity of the affected vessels and increased risk of blood clot formation, the usual cause of a heart attack or stroke.
A population-based study of postmenopausal women, aged 60–79 years, found that women aged 60–69 with aortic calcifications had lower vitamin K intakes than those without aortic calcifications, but this was not true for older women (18).
A prospective cohort study in 807 men and women, aged 39–45 years, did not find a correlation between dietary vitamin K1 intake and heart (‘coronary’) artery calcification (19). Additionally, vitamin K1 intake was not associated with calcification of breast arteries in a cross-sectional study of 1,689 women, aged 49–70 years (20).
The mechanism, by which vitamin K may promote mineralization of bone while inhibiting mineralization (calcification) of vessels, is not entirely clear (21, 22, 23), and needs further investigation.
Breast-fed infants in particular have a low vitamin K status because placental transfer of vitamin K is poor and human milk contains low levels of vitamin K. The concentrations of plasma clotting factors are low in infants due to immaturity of the liver (24).
Newborn infants have a risk of vitamin K deficiency, which may result in fatal bleeding within the skull (‘intracranial haemorrhage’) in the first weeks of life. Hemorrhagic disease in the newborn is a significant worldwide cause of infant morbidity and mortality.
Therefore, in many countries vitamin K is routinely administered prophylactically to all newborns.
Authored by Dr Peter Engel in 2010, reviewed and updated by Dr Szabolcs Peter on 18.06.2017
