I don't know about you, but in the alphabet soup of vitamins (A, B, C, E...) I've never heard much about vitamin K. It turns our that vitamin K is essential for regulating calcium balance in our body. A deficiency in vitamin K can be related to brittle bones and hardening of the arteries due to arterial calcification. Let's talk about bones first....
Vitamin K provides two benefits to the bone. In our bones, calcium is constantly undergoing adsorption and degradation (resorption). Vitamin K helps to prevent excessive calcium degradation which leads to brittle bones. Vitamin K also supports new bone formation by pulling calcium from our blood and causing it to stick to our bones. Vitamin D acts with K to assist calcium in bone protection.
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 ten years. In an analysis of this cohort, women whose vitamin K intakes were in the lowest quintile (1/5) had a 30% higher risk of hip fracture than women with vitamin K intakes in the highest four quintiles (23). A study in over 800 elderly men and women, followed in the Framingham Heart Study for seven years, found that men and women with dietary vitamin K intakes in the highest quartile (1/4) had a 65% lower risk of hip fracture than those with dietary vitamin K intakes in the lowest quartile (approximately 250 mcg/day vs. 50 mcg/day of vitamin K).
A recent study from the University of Toronto found little difference in bone mineral density and vitamin K supplemention. My hunch here was that vitamin K was not supplemented with other nutrients essential for bone building. It's like having one great player but no team. It's also highly probable that food sources of vitamin K are what the body utilizes, not synthetic supplements. [This is becoming a comon theme in nutrition - synthetic supplements are the same as nutrient from food!] Despite this finding, there were two surprises: "compared to placebo group women, women who took vitamin K over the four-year period had fewer fractures (9 vs. 20 women) and fewer cancer incidences (3 vs. 12 women)."
Great food sources of vitamin K for your diet include: dark leafy veggies, seeds (sesame, sunflower, pumpkin), eggs.