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Dietitian Judy Lee instructs study volunteer on the foods to be eaten as part of the study.

Read: More about vitamin K research in Agricultural Research magazine.

Did You Get Enough K Today?

By Judy McBride
January 10, 2000

If you’re between the ages of 18 and 44, chances are you didn’t get enough vitamin K today--or any other day, according to a survey by the Agricultural Research Service and a private company.

Vitamin K, long known for its role in blood clotting, is gaining recognition for its importance to the integrity of bones: It activates at least three proteins involved in bone health.

Sarah Booth at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University in Boston collaborated with Proctor & Gamble Company researchers to estimate vitamin K intake from a nationwide sample of 4,741 men, women and children.

People over age 65 consumed more phylloquinone--the most common form of vitamin K--than 20- to 40-year-olds. Only half the females age 13 and older--and less than half the males--got the Recommended Dietary Allowance, based on food intake diaries the survey volunteers kept for 14 days. The RDA is 65 micrograms per day for adult females and 80 mcg/day for adult males.

Phylloquinone is found in some oils, especially soybean oil, and in dark-green vegetables such as spinach and broccoli. One serving of spinach or two servings of broccoli provide four to five times the RDA.

In another study, with Yale University School of Medicine, Booth found that people absorb vitamin K just as well from broccoli as they do from oil. That’s contrary to the accepted notion that this fat-soluble vitamin is better absorbed from oil or oil-based supplements than from vegetables, with their high water content.

The study also showed that elders can benefit just as much as younger people from increasing vitamin K intake. The 60- to 80-year-old volunteers increased their blood levels from a high-K diet as readily as the 20- to 40-year-olds.

Read more about vitamin K research in the January issue of Agricultural Research magazine. 

ARS is USDA’s chief scientific arm.

Scientific contact: Sarah L. Booth, Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University, Boston, Mass., phone (617) 556-3231, fax (617) 556-3149;