Reduced levels of circulating vitamin K are linked to an increased risk of mobility limitation and disability in older adults, according to a study published in the Journals of Gerontology: Series A.
Shea et al examined the association between vitamin K status and incident mobility disability in the Health, Aging, and Body Composition Study. Image credit: Coombesy.
In humans and other vertebrates, vitamin K is required for blood coagulation and bone and vascular metabolism.
It naturally exists in two forms: vitamin K1 (also known as phylloquinone) and vitamin K2 (a group of compounds called menaquinones). Vitamin K3 (menadione) is a synthetic form of vitamin K.
Phylloquinone, the major dietary form of vitamin K, is widely distributed in green and leafy vegetables such as spinach, kale and broccoli. Menaquinones exist preferentially in meats, eggs, curd, cheese and fermented soyabeans.
For an average adult, one cup of raw spinach provides 145 micrograms (mcg) of vitamin K1, or 181% of the daily value; one cup of raw kale provides 113 mcg, or 141%; and half of a cup of chopped boiled broccoli provides 110 mcg, or 138%.
“Low vitamin K status has been associated with the onset of chronic diseases that lead to disability, but the work to understand this connection is in its infancy,” said Dr. Kyla Shea, a nutrition scientist in the Vitamin K Laboratory at the Jean Mayer USDA Human Nutrition Research Center on Aging (HNRCA) at Tufts University.
“Here, we’re building on previous studies that found that low levels of circulating vitamin K are associated with slower gait speed and a higher risk of osteoarthritis.”
Dr. Shea and colleagues examined two biomarkers: circulating levels of vitamin K and a functional measure of vitamin K (plasma ucMGP).
They used data from 635 men and 688 women ages 70-79 years old, who participated in the Health, Aging, and Body Composition Study (Health ABC).
Mobility was assessed every six months for 6 to 10 years through annual clinic visits and phone interviews in the intervening time.
For the analysis, the researchers defined mobility limitation as two consecutive semi-annual reports of having any amount of difficulty either with walking a quarter of a mile or climbing 10 steps without resting, and mobility disability as two consecutive semi-annual reports of having a lot of difficulty or inability to walk or climb the same amount.
They found that older adults with low levels of circulating vitamin K were more likely to develop mobility limitation and disability.
The other biomarker, plasma ucMGP, did not show clear associations with mobility limitation and disability.
Specifically, older adults with low circulating vitamin K levels were nearly 1.5 times more likely to develop mobility limitation and nearly twice as likely to develop mobility disability compared to those with sufficient levels. This was true for both men and women.
“The connection we saw with low levels of circulating vitamin K further supports vitamin K’s association with mobility disability,” said Dr. Sarah Booth, a nutrition researcher and director of the HNRCA at Tufts University.
“Although the two biomarkers we looked at are known to reflect vitamin K status, biomarker levels can also be affected by additional known or unknown factors. Further experiments to understand the mechanisms of biomarkers and vitamin K and their role in mobility are needed.”
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M. Kyla Shea et al. Vitamin K Status and Mobility Limitation and Disability in Older Adults: The Health, Aging, and Body Composition Study. Journals of Gerontology: Series A, published online May 6, 2019; doi: 10.1093/gerona/glz108
