A new, multi-ethnic study found older adults with low vitamin K levels more likely to die within 13 years compared with those whose vitamin K levels were adequate. The data suggest that vitamin K, a nutrient found in leafy greens and vegetable oils, may offer protective health benefits as people get older, according to the researchers.

A meta-analysis was conducted, involving approximately 4000 Americans from 54 to 76 years of age, one-third of whom were non-white. The participants were categorized according to their vitamin K levels and heart disease. However, those with the lowest vitamin K levels had a 19% higher risk of death, compared with those whose vitamin K levels reflected adequate vitamin K intake. 

Participants on the blood thinner warfarin were excluded because vitamin K counteracts the anti-clotting effects of warfarin, according to the study authors. Additionally, 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 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 study author Kyla Shea in a press release.

The limitations to the study include that circulating phylloquinone was measured from a single blood draw, rather than from repeated blood tests over time. Further, there were fewer heart disease events compared with total deaths, which may have limited researchers' ability to detect statistically significant risk of heart disease. 

The study authors concluded that this study cannot establish a causal relationship between low vitamin K levels and risk of death because it is observational, although the study adds existing evidence that vitamin K may have protective health benefits. 

Multi-ethnic study suggests vitamin K may offer protective health benefits in older age. TuftsNow. https://now.tufts.edu/news-releases/multi-ethnic-study-suggests-vitamin-k-may-offer-protective-health-benefits-older-age. Published June 15, 2020. Accessed June 16, 2020.