Vitamin D, often called the “sunshine vitamin,” plays a crucial role in keeping the body healthy. For example, it helps to absorb calcium, which strengthens bones and muscles. It also supports the immune system. But for individuals with kidney disease, vitamin D becomes even more important — and sometimes more complex.

This article explores the relationship between vitamin D and kidney health, including how it affects those with chronic kidney disease (CKD) and rare kidney conditions.

What Is Vitamin D and Why Is It Important?

Vitamin D is a fat-soluble vitamin, meaning the body absorbs it easily and stores it in fat. It helps the body absorb calcium and phosphorus, two minerals important for building and maintaining strong bones. Beyond supporting bone health, vitamin D strengthens the immune system, helps reduce inflammation, and may even help protect the heart.

The body naturally produces vitamin D when skin is exposed to sunlight. It can also be found in foods like fatty fish, fortified (boosted with nutrition) foods such as milk and cereals, and supplements. However, the vitamin D from sunlight, food, and supplements is inactive and must go through several steps in the body before it can be used.

First, the liver converts vitamin D into an inactive form called calcidiol. Then, the kidneys help turn calcidiol into calcitriol, the active form of vitamin D. Calcitriol is what allows vitamin D to perform its key functions in the body.

When kidney function is reduced due to kidney disease, the body may not make enough calcitriol. This can lead to weaker bones and other health problems. That’s why understanding the connection between vitamin D and kidney disease is so important.

Do People With Kidney Disease Need Vitamin D Supplements?

For those with kidney disease, getting enough vitamin D is especially important. Kidney disease often interrupts the body’s ability to handle vitamin D, leading to a lack of vitamin D that can worsen health problems. This is because damaged kidneys are less able to convert vitamin D into calcitriol, its active form.

Whether someone needs a vitamin D supplement depends on the type and stage of their kidney disease.

Stage 3-5 Kidney Disease

Individuals with kidney disease, especially in stages 3 to 5, are more likely to experience vitamin D deficiency (lack of vitamin D). Because of this, doctors recommend supplements to prevent bone disorders and parathyroid disorders that are triggered by the low levels of vitamin D.

Dialysis Considerations

For people on dialysis, managing vitamin D can become even more challenging. Dialysis helps remove waste products from the blood and keeps essential minerals balanced. However, if you’re on dialysis, your vitamin D levels may be much lower than those of people with CKD who aren’t on dialysis or who have received a kidney transplant.

Rare Kidney Diseases

Certain kidney conditions, like nephrotic syndrome and Alport syndrome, may also lead to vitamin D deficiencies. In nephrotic syndrome, the body loses too much protein in the urine, including proteins that help with binding vitamin D. This makes it harder for the body to absorb calcium and keep bones strong.

Why Are People With Kidney Disease More Likely To Be Deficient in Vitamin D?

Vitamin D deficiency is common among people with kidney disease for several reasons.

Reduced Kidney Function

As mentioned earlier, the kidneys play a crucial role in activating vitamin D. When kidney function declines and kidney tissue is damaged, this process slows down or may even stop.

Diet Restrictions

Many people with kidney disease follow special diets to control potassium and phosphorus levels. This can make it harder to eat enough vitamin D-rich foods like dairy products, fatty fish, and fortified cereals.

Limited Time in the Sun

Chronic illness can lead to less time spent outdoors, reducing exposure to sunlight — the body’s main natural source of vitamin D.

Protein Loss in Rare Conditions

In rare kidney diseases like nephrotic syndrome, too much protein is lost in the urine. Since vitamin D attaches to certain proteins in the blood, this protein loss can lower vitamin D levels as well.

Health and Life Expectancy in Kidney Disease

Research suggests that taking or consuming extra vitamin D may provide several health benefits for people with kidney disease. However, its effects depend on a person’s overall health, how serious their kidney disease is, and how well their treatment plan is managed.

Potential Benefits of Vitamin D for Those With Kidney Disease:

• Bone health — Vitamin D helps the body absorb calcium, which keeps bones strong and lowers the risk of fractures (broken bones).
• Parathyroid hormone (PTH) levels — Vitamin D supplements can help reduce high PTH levels, lowering the risk of bone-related problems.
• Immune function — Vitamin D has anti-inflammatory properties that may support overall immune health, which is particularly important for people with reduced kidney function.
• Heart health — Some studies suggest that vitamin D may help reduce heart disease risks, but larger studies are needed to confirm this.

Does Vitamin D Help People Live Longer?

While vitamin D supplements may improve quality of life and reduce the risk of complications, their direct impact on life expectancy is unclear. So far, research has not strongly proved that vitamin D extends life, but many factors — like other health conditions — may play a role.

Regular checkups with a doctor or nephrologist (kidney specialist) are important to ensure the best possible outcomes.

Important Points About Vitamin D Supplementation

Although vitamin D supplements can be beneficial for people with kidney disease, it’s important to use them carefully. Taking too much vitamin D can cause hypercalcemia (high calcium levels), especially in people undergoing dialysis. This can lead to serious health issues, such as vascular calcification (hardening of blood vessels) and kidney stones.

Consult a Healthcare Provider

If you have kidney disease, always talk to a doctor or nephrologist before starting any supplement. They can determine the right type and dosage for your specific condition. They can also monitor you with regular blood tests.

Avoid Over-the-Counter Supplements

Many people with kidney disease require specific prescription forms of vitamin D, such as cholecalciferol, ergocalciferol, calcifediol, calcitriol or doxercalciferol. These medications are carefully chosen based on a person’s kidney function and vitamin D levels.

Choose Carefully

If your doctor does recommend an over-the-counter vitamin D supplement, ask for guidance on choosing a trusted brand. Unlike prescription medications, supplements are not strictly regulated by the U.S. Food and Drug Administration (FDA). Some products may contain more or less vitamin D than the label states or have unlisted ingredients or contaminants.

How Can People With Kidney Disease Get Vitamin D?

Besides supplements, people with kidney disease can increase their vitamin D levels through food and safe sun exposure. However, some food choices may need to be limited due to kidney-friendly diet restrictions. Those with kidney disease should consult a dietitian to ensure these foods fit within their diet guidelines.

Food Sources

Some food sources of vitamin D include:

• Fatty fish (salmon, mackerel, and sardines)
• Egg yolks
• Fortified foods like milk, orange juice, and cereal

Sunlight

Spending from five to 30 minutes in the sun a few times a week can boost vitamin D production. However, individuals should balance this with the risk of skin cancer and other sun-related concerns. Wearing sunscreen with an SPF of 30 or higher and avoiding outside time during peak hours (10 a.m. to 4 p.m.) can help reduce the risk of sun damage.

Talk With Others Who Understand

MyKidneyDiseaseTeam is the social network for people with rare kidney diseases and their loved ones. On MyKidneyDiseaseTeam, members come together to ask questions, give advice, and share their stories with others who understand life with rare kidney disease.

Have you wondered about vitamin D supplementation with kidney disease? Share your experience in the comments below, start a conversation by posting on your Activities page, or connect with like-minded members in Groups.