With the help of sunlight, a healthy body can produce the extremely important vitamin D itself. Nevertheless, many people take preparations, especially in winter. Experts warn: A vitamin D overdose can be dangerous.
It’s the same thing with dietary supplements: millions of people swear by them, a gigantic industry makes good money from them – while most experts advise against them. The opinion of the experts: Vitamin preparations etc. should only be taken by those who have a medically diagnosed deficiency or increased need. And even then you have to pay attention to the correct dosage – because an overdose can have consequences, and not just with vitamin D.
Vitamin D: Why it’s so important
Vitamin D is essential for building and maintaining strong bones and is also involved in other metabolic processes. The body can produce most of the vitamin itself with the help of sunlight; the rest is obtained through food. The scientific consensus is: A healthy body that regularly exposes the skin to sunlight can store vitamin D produced in muscle and fat tissue in summer and draw on this storage in winter.
However, an undersupply can occur. The risk groups for this include people who rarely or never go out in the sun with uncovered skin and older people, especially women. Certain illnesses and medications can also cause a vitamin D deficiency. Anyone who starts the winter with a poorly filled storage tank can develop a deficiency in the dark months. Long-term vitamin D deficiency can lead to serious health consequences such as muscle weakness, bone pain and osteoporosis.
Anyone who has reason to believe that they are suffering from a vitamin D deficiency should definitely seek medical advice. The vitamin D level can be determined using a blood test. On medical advice, it may then be necessary to take vitamin D preparations in a predetermined dose.
Vitamin D preparations: often unnecessary, often overdosed
Vitamin D is one of the most popular dietary supplements and vitamin D blood tests are one of the most common IGel services, i.e. privately paid examinations by family doctors. At some point, people apparently became aware of how important vitamin D is for health. But it seems that many people are overstepping the mark.
Medical specialist organizations and consumer protection organizations regularly advise against taking dietary supplements on your own. Institutions such as Öko-Test, Stiftung Warentest and consumer advice centers have been warning about excessively high doses of vitamin D preparations for years. Both Öko-Test and Stiftung Warentest repeatedly find doses of vitamin D in many dietary supplements that are too high. At Öko-Test, almost half of the products fail the current vitamin D test.
Vitamin D overdose: Current warning from the Federal Institute for Risk Assessment
In December 2023, the Federal Institute for Risk Assessment (BfR) published a new statement: “High-dose dietary supplements with vitamin D can have long-term health effects” is the title.
In agreement with other leading nutrition, health and consumer protection organizations such as the DGE, the RKI and the consumer advice centers, the BfR assumes: “Healthy people in Germany generally consume sufficient vitamins and minerals through a balanced and varied diet. “As a result, you don’t need any nutritional supplements, including vitamin D.
But it’s not just about not using it: overdoses can be dangerous. With regard to vitamin D, the BfR writes:
“In particular, long-term use of high-dose dietary supplements can pose health risks.”
What happens if you overdose on vitamin D?
First of all: Too much sunlight cannot cause a vitamin D overdose. This can only happen by taking supplements or medicines. Vitamin D is extremely important for strong bones – but a lot of vitamin D does not lead to particularly strong bones and muscles.
On the contrary: Too high amounts can lead to calcium being dissolved out of the bone substance. The calcium can then accumulate in the body’s vessels, tissues and organs and thus impair their function.
The BfR bases its assessment on documented cases of vitamin D “poisoning” in children and adults – a so-called hypercalcemia. This means extremely high calcium levels in the blood.
Symptoms of a vitamin D overdose (hypercalcemia) include:
- fatigue
- Muscle weakness
- Loss of appetite
- nausea
- Vomit
- constipation
- Cardiac arrhythmias
- weight loss
- Kidney stones (with persistent hypercalcemia)
- Renal calcification (with persistent hypercalcemia)
- Decrease in kidney function (with persistent hypercalcemia)
Older women in particular are often advised to take vitamin D pills because studies have shown that they have an increased risk of vitamin D deficiency. However, the BfR warns, citing a large number of studies: There is evidence from clinical studies that just 100 micrograms (4,000 IU) daily could reduce bone density and increase the risk of falls. The same dose, taken over a longer period of time, can make people with heart disease even sicker and has led to increased hypercalcemia in observations.
How much vitamin D is safe?
There have been debates among experts for years about the correct daily dose of vitamin D, especially when supplemented. According to the BfR and DGE, daily doses should not exceed 20 micrograms (800 IU) of vitamin D – this value applies to people who cannot produce or store vitamin D themselves. If you take preparations on your own, this dose is within a reasonably safe range.
“The use of high-dose vitamin D-containing food supplements to supplement the daily diet cannot be justified from a nutritional perspective, since consuming 20 μg (800 IU) of vitamin D per day is sufficient even without the skin being exposed to sunlight,” writes the BfR. Higher dosages should therefore be avoided or at least only taken under medical supervision.
The recommendations of the National Institutes of Health in the USA roughly correspond to those of the German BfR. The European Food Safety Authority (EFSA) sees the Tolerable Upper Intake Level (UL), i.e. the maximum daily intake that does not lead to health problems, at 100 micrograms (4,000 IU). Please note: This refers to the total amount, not the dosage of tablets – i.e. the amount of vitamin D that the body produces itself is included.
Experts agree that if a deficiency or increased need is diagnosed, higher doses are sometimes needed to ensure or restore an optimal vitamin D supply.
What does that mean for me?
- The best way to ensure healthy vitamin D levels and avoid an overdose is to expose yourself to the sun regularly – in moderation, of course, to protect your skin from sunburn.
- If you have reasonable doubts that your vitamin D level is OK, talk to your doctor and have a test done.
- If there is no evidence of a vitamin D deficiency or increased need, you probably do not need to take supplements.
- If you are taking vitamin D – due to a corresponding diagnosis – make sure to take a maximum daily dose of 20 micrograms, unless your doctor recommends higher doses, for example due to a severe deficiency.
- If you are currently taking higher doses, we recommend seeking medical advice.
- If you are taking vitamin D supplements and experience one or more of the above symptoms of a vitamin D overdose, seek medical advice.
- Babies and toddlers up to their first birthday (some experts recommend up to their second birthday in the winter months) should receive daily vitamin D doses of ten micrograms.
- In addition, according to the BfR, “a general vitamin D intake of up to 20 micrograms per day should only be considered” for nursing home residents.
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