Multi-ethnic study suggests vitamin K may offer protective health benefits in older age

June 15, 2020

BOSTON (June 15, 2020)-- A new, multi-ethnic study found older adults with low vitamin K levels were more likely to die within 13 years compared to those whose vitamin K levels were adequate. The results suggest vitamin K, a nutrient found in leafy greens and vegetable oils, may have protective health benefits as we age, according to the researchers.

The meta-analysis, involving nearly 4,000 Americans aged 54-76, one-third of whom were non-white, was led by researchers at the The American Journal of Clinical Nutrition.

The research team categorized participants according to their vitamin K blood levels. They then compared risk of heart disease and risk of death across the categories over approximately 13 years of follow-up.

The results showed no significant associations between vitamin K levels and heart disease. However, the people with the lowest vitamin K levels had a 19 percent higher risk of death, compared to the those with vitamin K levels that reflected adequate vitamin K intake.

Vitamin K is a nutrient that is important for maintaining healthy blood vessels. It is found in leafy greens, such as lettuce, kale and spinach, and in some vegetable oils, especially soybean and canola.

"The possibility that vitamin K is linked to heart disease and mortality is based on our knowledge about proteins in vascular tissue that require vitamin K to function. These proteins help prevent calcium from building up in artery walls, and without enough vitamin K, they are less functional," said first author

Shea is a scientist on the HNRCA's

"Similar to when a rubber band dries out and loses its elasticity, when veins and arteries are calcified, blood pumps less efficiently, causing a variety of complications. That is why measuring risk of death, in a study such as this, may better capture the spectrum of events associated with worsening vascular health," said last author

While this study adds to existing evidence that vitamin K may have protective health benefits, it cannot establish a causal relationship between low vitamin K levels and risk of death because it is observational. Additional studies are also needed to clarify why circulating vitamin K was associated with risk for death but not heart disease.

Methodology

The study is a meta-analysis, which combined data from participants in three ongoing studies: the

Participants on the blood thinner warfarin were excluded because vitamin K counteracts the anti-clotting effects of warfarin. All participants were free of heart disease at baseline and had vitamin K levels measured during a single medical exam that was part of each study's regular protocol.

The statistical analysis adjusted for age, gender, race, ethnicity, BMI, triglycerides, cholesterol levels, smoking status, and use of medications for diabetes or high blood pressure.

There are some limitations to the study, including that circulating phylloquinone was measured from a single blood draw, rather than from repeated blood tests over time. Higher circulating phylloquinone may reflect an overall healthier diet and lifestyle. Lastly, there were fewer heart disease events compared to total deaths, which may have limited researchers' ability to detect statistically significant risk of heart disease.
-end-
Authors and funding

Additional authors on the study are Kathryn Barger and Gregory Matuszek, of the USDA HNRCA; Mary Cushman, at University of Vermont's Larner College of Medicine; Emelia J. Benjamin of Boston University School of Medicine and Public Health; and Stephen B. Kritchevsky of Wake Forest School of Medicine's Sticht Center for Healthy Aging and Alzheimer's Prevention.

This work was supported by the National Institutes of Health's National Heart, Lung and Blood Institute (R21HL133421) and the U.S. Department of Agriculture's Agricultural Research Service. Any opinions expressed in this paper are those of the authors and not the funders.

Citation

Shea, M. K., Barger, K., Booth, S.L., Matuszek, G., Cushman, M., Benjamin, E.J., Kritchevsky, S.B., & Weiner, D.E. (2020). Vitamin K status, cardiovascular disease, and all-cause mortality: A participant-level meta-analysis of 3 US cohorts. The American Journal of Clinical Nutrition.
https://doi.org/10.1093/ajcn/nqaa082

About the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University

For four decades, the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University has studied the relationship between good nutrition and good health in aging populations. Tufts research scientists work with federal agencies to establish the Dietary Guidelines, the Dietary Reference Intakes, and other significant public policies.

Tufts University, Health Sciences Campus

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