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Vitamin D in Chronic Kidney Disease
Vitamin D is a well-known vitamin that some of us may think of as the “sunshine” vitamin. In your health classes growing up, you were likely taught the role of vitamin D in maintaining healthy bones.
While vitamin D is vital to bone health, it also has a key relationship with the kidneys. In this article, we will take a look at how kidneys and vitamin D interact, the types of vitamin D and food and supplement sources for vitamin D.
Types of Vitamin D
While there are many forms of vitamin D, the two major types are:
Cholecalciferol, vitamin D3
Ergocalciferol, vitamin D2
Vitamins D3 and D2 can be retrieved from sunlight or food. They are both considered nutritional vitamin D and are inactive in the body. Once absorbed, the liver changes it to a different form called calcifediol. Calcifediol is further transformed to the active form, calcitriol, in the kidneys.
Calcitriol is the active form of vitamin D. At this point, vitamin D now acts as a hormone, or messenger, to complete important roles in the body. These important roles involve bone health, cell growth, immune function and reduction of inflammation.
Kidney Disease and Vitamin D
Research shows that the majority of individuals with chronic kidney disease (CKD) are deficient in inactive vitamin D (2).
Researchers have found an association between low inactive vitamin D levels and the occurrence of a condition called secondary hyperparathyroidism (SHPT) in people with CKD (2).
SHPT is common among CKD patients, especially as kidney disease progresses. It occurs when the parathyroid gland becomes enlarged and releases too much parathyroid hormone (PTH). High levels of PTH lead the body to pull out calcium from the bones.
Overtime, this causes bones to weaken and calcium deposits to build up in tissues and organs, including the heart. If the heart becomes calcified, blood flow is reduced which may lead to a heart attack. Therefore, preventing or treating SHPT is important. Vitamin D is a big component of both treatment and prevention.
In studying individuals with CKD, researchers found a positive relationship between inactive vitamin D levels and active vitamin D levels (2). Therefore, if an individual has a low level of inactive vitamin D, correcting it may improve active vitamin D levels. In turn, this can help prevent hyperparathyroidism or serve as a treatment if already diagnosed.
Food Sources of Vitamin D
Only a handful of foods are naturally good sources of vitamin D. Fortunately, some common foods are also fortified with vitamin D.
Fish liver oils and flesh of fatty fish like tuna, mackerel and salmon contain the best sources of vitamin D. Smaller amounts of vitamin D can be found in beef liver, cheese, egg yolk and some types of mushrooms.
In the United States, most milk is fortified with vitamin D. Some brands of ready-to-eat cereal, orange juice, margarine and yogurt are also fortified with vitamin D.
Vitamin D Supplements
Recommendations for vitamin D supplements should be made by a physician. Recommendations by a doctor are based on current vitamin D levels along with sun exposure, diet and stage of CKD.
Types of Nutritional Vitamin D Supplements:
- Ergocalciferol (Vitamin D2)
- Cholecalciferol (Vitamin D3)
Vitamin D plays an important role in preventing and treating secondary hyperparathyroidism among CKD patients. If uncontrolled, weak bones and calcium build-up in tissues and organs is possible. If you are not on a vitamin D supplement, you may choose to discuss options with a doctor to get your vitamin D levels checked and see if supplementation would be appropriate.
For more information read our past post “Vitamin D Basics“.
Additional Kidney Diet Resources
Visit DaVita.com and explore these diet and nutrition resources:
DaVita Diet Helper online meal planner and tracker
Kidney Smart® Classes taught by kidney experts in your area
This article is for informational purposes only and is not a substitute for medical advice or treatment. Consult your physician and dietitian regarding your specific diagnosis, treatment, diet and health questions.