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Vitamin K does not improve vessel health after kidney transplant

10 May 2021

In research, discovering what doesn’t work is just as important as finding out what does.  

Taking vitamin K supplements does not improve blood vessel health in people with kidney transplants, according to new research funded by Kidney Research UK at the University of Glasgow.  

Blood vessels
Blood vessels

Risk to heart and blood vessels

People with kidney transplants are at very high risk of heart and blood vessel diseases, such as heart attacks and strokesThis is partly because their blood vessels are more likely to become stiff and calcified – calcium deposits build up on the blood vessel walls and they harden. Standard treatments to prevent heart and vessel diseases, such as aspirin or cholesterol-lowering tablets, do not work as well in people with kidney transplants so we need to find other ways to improve vessel health in these patients. 

Vitamins and vessel health

Vitamin K activates proteins in the body that can help prevent blood vessels from becoming stiff and calcified. It is found in the diet in cereals, grains, oils, dairy products, meats and especially in leafy green vegetables such as kale and broccoliPeople with kidney transplants tend to have low levels of vitamin K and this led researchers to believe that low vitamin K levels could be responsible for the decline in blood vessel health in these patients. The team believed that vitamin K supplements might top up the body’s stores, improve blood vessel health and reduce the risk of heart and vessel disease in people with kidney transplants. 

Vitamin K treatment alone did not improve vessel health

In the study, funded by Kidney Research UK and published recently in The American Journal of Transplantation, the research team gave people with kidney transplants vitamin K supplement tablets for one year and monitored their blood vessels. 

Dr Jennifer Lees, lead author of the study, said “We felt that it was important to test whether an inexpensive, low-risk treatment like vitamin K could improve blood vessel health in people with kidney transplants”. 

The team confirmed that the participants with kidney transplants had stiffer, more calcified blood vessels than people of the same age and sex without kidney disease and they also showed evidence of vitamin K deficiency. Although taking the supplement tablets meant that the patients were no longer deficient in vitamin K, researchers did not see any improvements in blood vessel stiffness or calcification. 

Dr Lees said, “Although we found that vitamin K treatment alone did not improve blood vessel stiffness or calcification, we have collected important information about how blood vessel health changes over time in people with kidney transplants, and some of the factors that may influence this change.” 

“Medical research is all about generating a hypothesis (or theory), testing that hypothesis, and then using your results to refine the question or to move on to try something else. Studies like ours are essential to allow science to progress. Ultimately, this will allow us to explore other promising treatment options for people with kidney transplants”.  

“We are extraordinarily grateful to the ViKTORIES participants and trial team for their time and enthusiasm, and to Kidney Research UK for funding the study.” 

Read the full paper: 

The ViKTORIES trial: a randomised, double-blind, placebo-controlled trial of vitamin K supplementation to improve vascular health in kidney transplant recipients - PubMed ( 

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