Vitamin K helps make four of the 13 proteins needed for blood clotting. Its role in maintaining the clotting cascade is so important that people who take anticoagulants such as warfarin (Coumadin) must be careful to keep their vitamin K intake stable.
Lately, researchers have demonstrated that vitamin K is also involved in building bone. Low levels of circulating vitamin K have been linked with low bone density, and supplementation with vitamin K shows improvements in biochemical measures of bone health. (1) A report from the Nurses’ Health Study suggests that women who get at least 110 micrograms of vitamin K a day are 30 percent less likely to break a hip than women who get less than that. (2) Among the nurses, eating a serving of lettuce or other green, leafy vegetable a day cut the risk of hip fracture in half when compared with eating one serving a week. Data from the Framingham Heart Study also shows an association between high vitamin K intake and reduced risk of hip fracture in men and women and increased bone mineral density in women. (3, 4)
People who do not regularly eat a lettuce salad or green, leafy vegetables are likely to be deficient in their intake of vitamin K; national data suggests that only about one in four Americans meets the goal for vitamin K intake from food. (5)
1. Weber P. Vitamin K and bone health. Nutrition. 2001; 17:880–7.
2. Feskanich D, Weber P, Willett WC, Rockett H, Booth SL, Colditz GA. Vitamin K intake and hip fractures in women: a prospective study. Am J Clin Nutr. 1999; 69:74–9.
3. Booth SL, Tucker KL, Chen H, et al. Dietary vitamin K intakes are associated with hip fracture but not with bone mineral density in elderly men and women. Am J Clin Nutr. 2000; 71:1201–8.
4. Booth SL, Broe KE, Gagnon DR, et al. Vitamin K intake and bone mineral density in women and men. Am J Clin Nutr. 2003; 77:512–6.
5. Moshfegh A, Goldman, J., Cleveland, L. . What We Eat In America. NHANES 2001–2002: Usual Nutrient Intakes from Food Compared to Dietary Reference Intakes. U.S. Dept. of Agriculture, Agricultural Research Service. 2005.