Vitamin D supplements do not increase risk of kidney stones

Kidney stones are considered a possible complication of daily vitamin D supplementation. A new study debunks this hypothesis and points to its advantages.

Lynn Zimmerman/t-online

Vitamin D is an important substance. The body needs it to maintain a strong immune system and produce certain hormones. However, only about half of adults and adolescents have an adequate supply of vitamin D, according to the Robert Koch Institute (RKI).

That's why many people turn to vitamin D supplements, especially during the dark seasons. But critics point out that taking vitamin D regularly could carry the potential risk of overdose, especially if taken without a doctor's prescription. A current DKFZ study shows that this fear is unfounded. Experts say daily intake of vitamin D does not increase the worrisome risk of kidney stones or atherosclerosis. The study was published in the journal Nutrients.

Vitamin D affects calcium balance

The reason for warning about too much vitamin D is that it has a significant impact on calcium metabolism. On the one hand, vitamin D causes the intestines to absorb more calcium, and on the other hand, the kidneys excrete less calcium. If you overdose on vitamin D, you run the risk of what's called hypercalcemia, which is an increase in calcium levels in the blood. In the worst cases, this can lead to kidney stones and hardening of the arteries (atherosclerosis).

To study how different amounts of vitamin D affect calcium levels, DKFZ researchers analyzed data from more than 400,000 people. 4.3% of participants said they took vitamin D supplements regularly. Another 20.4% take multivitamin supplements that also contain vitamin D.

How much vitamin D do we need?

In theory, the body can produce enough vitamin D on its own as long as the skin is exposed to adequate sunlight. However, the RKI notes that vitamin D production mainly takes place at this latitude between March and October. One way to improve your vitamin D status is to take supplements (food supplements).

However, the German Nutrition Society has so far only recommended this for members of certain risk groups, such as the elderly or dark-skinned people. The reference value for vitamin D intake is 20 micrograms per day, which is equivalent to 800 international units (IU) if the body cannot produce it naturally. This estimate, derived from DGE research, applies to all age groups over one year old. Infants under 12 months of age need 400 IU per day.

No kidney stones despite high calcium content

The results were surprising: The subjects who took vitamin D regularly had higher average calcium levels. However, over a nearly 13-year observation period, they were no more likely to develop atherosclerosis or kidney stones than those who did not take vitamin D.

“This is the largest study in the world to date to examine the dose-response relationship between vitamin D supplementation and safety in calcium metabolism. “Happily, we were unable to identify a link to increased calcium concentrations in the blood that can be traced There is any link to the disease,” study author Dr. Ben Shottke.

Therefore, the authors concluded that high calcium levels may not be caused by taking vitamin supplements. They suspect there are other reasons behind the symptoms, such as genetic factors. Another possibility: Health-conscious people who take vitamin D regularly may also make greater use of calcium supplements.

Overdose starting from 10,000 IU per day

According to lead author Dr. Shasha, the study results show that taking vitamin D supplements is considered safe. This was not surprising to her, as vitamin D overdose only occurs when taking “extremely high doses” over a long period of time.

According to her, the usual vitamin D dose in the EU is 400 to 4,000 international units (IU) per day. On the other hand, overdose side effects have only been observed in clinical studies with daily doses of 10,000 IU, Dr. Sasha.

Instead, the German Cancer Research Center noted that it was able to find another important advantage in summarizing all meaningful clinical studies on vitamin D. Therefore, cancer patients taking vitamin D can reduce the risk of dying from cancer by 12% if taken daily.

“Adequate vitamin D supplementation, tailored to needs, can make an important and very cost-effective contribution to preventing cancer deaths and various diseases,” adds co-author Professor Hermann Brenner.

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