Vitamin K Research

In a recent article in Current Opinion in Clinical Nutrition and Metabolic Care, Sarah Booth, PhD, lab director of the Vitamin K Laboratory at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University (USDA HNRCA), reviewed studies regarding vitamin K status among the elderly. Although older adults seem to consume more vitamin K than younger adults, many seniors are still not meeting the recommended intake of vitamin K.

"Research has shown poor vitamin K intake may be associated with conditions such as bone fractures, bone loss, hardening of the arteries, and osteoarthritis," says Booth, who is also a professor at the Friedman School of Nutrition Science and Policy at Tufts.

Although it may be important for the elderly to increase dietary vitamin K, Booth notes that it is also essential for researchers to examine factors other than diet that may affect vitamin K status in the body. "One promising area of research is the interrelationship between estrogen and vitamin K," says Booth, "as studies indicate that low estrogen levels in menopause may change the way vitamin K is metabolized. More research is also needed to determine vitamin K status of elderly men, as well as to determine what populations, if any, might benefit from vitamin K supplements."

In a study published in Nutrition, Metabolism & Cardiovascular Diseases, Booth and colleagues examined dietary patterns of more than 40,000 men to determine if phylloquinone, the form of vitamin K found in plant sources like leafy green vegetables, could serve as a marker for reduced risk of developing cardiovascular disease.

Booth and colleagues, including corresponding author Arja Erkkila, PhD, of both the USDA HNRCA and the University of Kuopio in Finland, determined that high phylloquinone intake did not appear to be an independent risk factor for cardiovascular disease. However, men consuming high amounts of phylloquinone generally had better dietary habits, such as eating more fruits and vegetables and less saturated fat. Men consuming high amounts of phylloquinone were also less likely to smoke and more likely to exercise or take dietary supplements.

The association between high phylloquinone intake and a healthy diet and lifestyle led Booth and colleagues to conclude that phylloquinone intake could indeed play an important role in cardiovascular research studies. "...In large population groups, phylloquinone may provide a more robust assessment of overall cardiovascular risk status than assessing multiple individual diet and lifestyle habits," write the authors.

The Vitamin K Laboratory, as part of the Agricultural Research Service (ARS) National Food and Nutrient Analysis Program, has been contributing vitamin K food content data to the National Nutrient Databank for nearly a decade. For more information on vitamin K research at the USDA HNRCA, refer to "Tufts Researchers are Keeping Track of Vitamin K" in the May/June 2006 issue of Friedman Nutrition Notes [http://nutrition.tufts.edu/news/notes/2006-05.html]. The ARS is the chief scientific research agency of the USDA.