Can Vitamin K Reverse or Prevent Vascular Calcification in CKD?
Vitamin K is a fat-soluble vitamin that is necessary for the clotting of blood and also plays an important role in building bone. Vitamin K is available from green leafy veggies like kale, cabbage, lettuce, collard greens, and spinach. In addition, it is also found in small amounts in fermented foods, animal meat, and dairy products. Besides, bacteria inside the colon can also manufacture vitamin K.
Even though vitamin K is stored in tissues like the liver, it is rapidly used up and also broken down. Thus, a constant supply of vitamin K from a food source is necessary to prevent deficiency.
Deficiency of vitamin K
Deficiency of vitamin K is rare in adults but may occur in some individuals who take medications that block the synthesis and absorption of vitamin K like certain antibiotics or in people who are not able to absorb nutrients from the intestine.
Vitamin K deficiency is not that rare in newborns because the mother’s vitamin K does not cross the placenta. Thus, to prevent bleeding in newborns after birth, vitamin K is usually administered.
The adequate intake of vitamin K for men is 120 micrograms per day and for women, it is 90 micrograms/day.
Calcification and kidney disease
In individuals with chronic kidney disease (CKD), the most common cause of death is heart disease. Studies show that calcification of the vessels is a very strong predictor of heart disease in these individuals. When the vessels become calcified, they not only become thickened but also lose their elasticity. More important calcification is also associated with the formation of atherosclerotic plaques that narrow the vessel and prevent blood from reaching the target cells.
Studies show that as kidney function deteriorates, the risk of developing vascular calcification also increases and compromises blood flow to many organs including the heart. Calcification in blood vessels in individuals with chronic kidney disease occurs much earlier than in the general population. Over the years, it has been shown that calcification of vessels is associated with many adverse outcomes including heart disease and sudden death. Therefore, a significant amount of research has been devoted to reversing or preventing calcification in individuals with chronic kidney disease.
What are the risk factors for calcification in individuals with CKD?
Traditional risk factors for vascular calcification include:
- Male gender
- Advanced age
- High blood pressure
- High cholesterol levels
Additional risk factors in kidney individuals:
- A decline in kidney function
- Altered metabolism of minerals
- High levels of phosphate
- High calcium levels
- Increased levels of parathyroid hormone
- Vitamin D deficiency
It is felt that there is a delicate balance between mineral deposition and resorption ongoing in blood vessels and any disturbance can result in calcification of the vessel wall.
So how is vascular calcification treated and or prevented?
Because vascular calcification is associated with a very high risk of heart disease and death in CKD individuals, prevention is crucial. Current treatment strategies include the following:
- Control the blood pressure
- Ensure blood glucose levels are within normal
- Ensure levels of phosphate and calcium are within normal
Unfortunately, the control of the traditional risk factors for vascular calcification has not been shown to prevent or completely reverse vascular calcification in individuals with CKD. Most studies show that once vascular calcification has been established, it tends to progress, and very rarely can it be arrested or reversed.
Ideally, treatment should focus on the prevention of vascular calcification very early in individuals who have been diagnosed with CKD, but even then this only prevents vascular calcification in less than half of the individuals. Even though phosphate binders are recommended in an individual with CKD, there is not enough evidence to support their use for preventing calcification.
Other researchers have tried Vitamin D with calcium but this combination did not reduce the risk of heart disease or death in individuals undergoing dialysis.
Vitamin K and vascular calcifications
Overall it has been noted that individuals with CKD tend to develop vitamin K deficiency very quickly, especially those on dialysis. In addition, subclinical vitamin K deficiency is quite common in these patients especially those who are being treated with warfarin (blood thinner).
More important studies show that there is a lower risk of heart disease and death in individuals with a high intake of vitamin K, but this is not a universal observation. Why vitamin K is associated with a lower risk of calcification and death in some individuals with CKD is not known.
Several studies show that vitamin K administration can delay the progression of calcification and worsening of vessel elasticity but unfortunately, these findings are not seen in all individuals treated with vitamin K.
There is no question that vitamin K has many health benefits including prevention of vessel calcification and reducing the risks of heart disease and improving bone strength. Whether these observations are limited to only a few individuals with CKD or just placebo effects is not known. Until larger clinical trials are done, empirically administering vitamin K to individuals with CKD should be refrained; at the other extreme, vitamin K can also initiate more clotting problems, which may lead to additional complications.
Vascular calcification is an important risk factor for increased risk of death and heart attacks in individuals with CKD. It is an active process that is associated with altered mineral metabolism but to date no one treatment has been found to be effective in slowing its progression. Vitamin K has been found to slow down calcification in CKD but this is not a universal observation. At the moment, there is no solid evidence to support its use in all individuals with CKD.