Vitamin K important for blood and bones - Brief Article

Nutrition Health Review, Winter, 2002

Vitamin K, usually associated with leafy green vegetables, is an important factor in proper blood clotting and bone metabolism. Researchers at the Jean Mayer U.S. Department of Agriculture (USDA) Human Nutrition Research Center on Aging at Tufts University, Boston, along with the USDA Nutrient Data Laboratory in Beltsville, Maryland, has found that vegetable oils are also an excellent source of vitamin K.

To attain a more comprehensive understanding of vitamin K content of various fats and oils used by consumers in the U.S., the researchers analyzed margarines, spreads, butters, shortening, vegetable oils, and salad dressings.

Their results showed that vitamin K content decreased with hydrogenation, the process of converting liquid oils to semisolid forms by adding hydrogen molecules to the fatty acid. Butter was shown to contain less vitamin K than vegetable-derived oils and spreads, corroborating the current USDA dietary guidelines recommending that consumers obtain most of their dietary fat from nonhydrogenated vegetable sources. The concentration of vitamin K varied according to fat content, which is why reduced-fat salad dressings contain lower amounts of the vitamin.

The guidelines suggest that women take in 90 micrograms of vitamin K a day, while the adequate intake (AI) requirement for men is 120 micrograms. One tablespoon of margarine would be equal to about 10 percent of the AI for men and 13 percent for women; two tablespoons of regular salad dressing provides 25 percent and 33 percent of the AI for men and women, respectively.