Vitamin D is produced by the body itself with the help of UV radiation. But how much vitamin D does the body actually need and how long should you stay outside?

The body needs vitamin D to utilize calcium and phosphorus properly and thus contributes to healthy bones, teeth and muscles. vitamin D also has a special status among vitamins: it is produced by the skin itself with the help of sunlight. But how much vitamin D does the body need per day?

How much vitamin D does the body need per day?

The German Nutrition Society (DGE) has published estimates for the daily requirement of vitamin D. According to the DGE, anyone who spends enough time in the sun every day does not need additional vitamin D. The following values ​​therefore only refer to days when the body cannot produce vitamin D itself:

  • Infants (0 to less than 12 months): 10 µg/day
  • Children (1 to under 15 years): 20 µg/day
  • Adolescents and adults (15 to under 65 years): 20 µg/day
  • Adults (65 years and older): 20 µg/day
  • Pregnant women: 20 µg/day
  • Breastfeeding women: 20 µg/day

Many vitamin D preparations are not given in µg/day, but in international units (IU). According to the DGE, these are converted as follows:

  • 1 µg = 40 International Units (IU); 1 IU = 0.025 µg

In other words, this applies to children and adults: According to the DGE, anyone who has not spent enough time in the sun for a long period of time could contribute to an adequate vitamin D supply by taking preparations with a dosage of 800 IU.

The guidelines for daily requirements vary greatly internationally: The National Health Service (NHS) in the United Kingdom, for example, gives a guideline value of 400 IU – half of the DGE. The National Institute of Health in the USA recommends 600 IU. The Endocrine Society states that adults may need 1500 to 2000 IU to keep blood levels above 30 ng/ml. This shows that even official authorities worldwide are not yet in complete agreement on the subject. The need for vitamin D is very individual. This is also why the dosage is adjusted to body weight in the event of a deficiency. As a rough guideline: 10,000 IU increases the vitamin D level by 1 ng/ml.

Internist and metabolism expert Helena Orfanos-Boeckel writes in her book “Nutritional Therapy” that the need for vitamin D is very individual and therefore varies greatly. According to the doctor, some people can maintain blood levels of 50 ng/ml with 800 IU, while others need 10,000 IU to achieve the blood levels. On average, patients in her practice with skin types II to IV need around 4,000 IU daily. According to Helena Orfanos-Boeckel, all doses over 2,000 IU should be in the hands of a doctor. A sensible therapy can only be developed with laboratory diagnostics.

There are also some vitamin D tablets on the market that have a very high dosage of 20,000 IU. These should only be taken after consulting a doctor. The first symptoms of a vitamin D overdose can be nausea or vomiting. Long-term use can have serious consequences, as vitamin D is a fat-soluble vitamin that is stored in the body.

Video: SAT.1

Sun rays: This is how much vitamin D the body needs

To ensure a sufficient supply of vitamin D, the DGE recommends spending a total of five to 25 minutes in the sun per day, depending on the season. Since vitamin D is produced through the skin, the face, hands and arms should not be covered with clothing.

The amount of time you can spend in the sun without turning red depends on your skin type. Lighter skin types (1 to 3) should be careful when sunbathing. According to the Federal Office for Radiation Protection, you should estimate the UV dose that would cause you to get sunburn and only spend half the time in the sun accordingly.

According to the Robert Koch Institute (RKI) are at risk for vitamin D deficiency. Due to the higher pigmentation of the skin, the UV rays that are necessary for the production of vitamin D cannot penetrate well. So you have to spend significantly more time in the sun to have a sufficient vitamin D level in your body. According to the Swiss Federal Office of Public Health, you can use the following times as a guide depending on your skin type:

Special UV-sensitive people with fair skin and children

Late morning Midday Afternoon
January and December >4 hours 1.5 to 2.5 hours too little Exposure
February and November 2.5 to 3.5 hours 30 min to 1.5 h 2 to 3 hours
March and October 1 to 2 hours 15 minutes to 30 minutes 30 min to 3 hours
April and September 30 to 45 minutes 10mins 15 to 30 minutes
May and August 15 to 30 minutes 5 to 10 minutes 10 to 15 minutes
June and July 15 to 20 minutes 5 to 10 minutes 10 to 15 minutes

Vitamin D for normal UV-sensitive people with medium-light skin

Late morning Midday Afternoon
January and December >5 hours 2 to 7 hours too little Exposure
February and November 3 to 5 hours 45 min to 2.5 h too little Exposure
March and October 1 to 2 hours 30 to 45 minutes 45 min to 2.5 h
April and September 45 to 60 minutes 10 to 20 minutes 20 to 60 minutes
May and August 20 to 45 minutes 10 to 15 minutes 15 to 30 minutes
June and July 20 to 30 minutes 10 to 15 minutes 15 to 20 minutes

People with dark skin who are less sensitive to UV rays

Late morning Midday Afternoon
January and December >7 hours too little Exposure too little Exposure
February and November 4 to 8 hours 1.5 hours to 5 hours too little Exposure
March and October 2 to 4 hours 45 min to 1.5 h too little Exposure
April and September 60 to 120 minutes 20 to 60 minutes 45 min to 3.5 h
May and August 45 to 90 minutes 20 to 30 minutes 30 to 60 minutes
June and July 40 to 75 minutes 20 to 30 minutes 30 to 60 minutes

As can be seen from the table, people in Germany who are not very sensitive to UV rays cannot get enough vitamin D from the sun’s rays between October and March. Even people with lighter skin would sometimes have to spend four hours outdoors to produce a total of 600 IU of vitamin D – which is not the case for many people because of the cold temperatures. Although the body draws on its vitamin D stores in fat and muscles in winter, taking additional supplements can be useful.

These tables should only serve as a guideline. The DGE also states that the individual need for UV light varies greatly. The duration of sun exposure also depends on the latitude.

Vitamin D levels: When does the body need more?

To check how much vitamin D is present in the body, a blood test is carried out. According to the RKI, the level is measured using 25-hydroxyvitamin D, a precursor to active vitamin D. Depending on the source, the values ​​are given in nanograms per milliliter (ng/ml) or nanomoles per liter (nmol/l). Here is the overview:

25(OH)D in ng/ml possible effects
<12

Vitamin D deficiency

Risk for:

  • Bone disease in children and adolescents (rickets)
  • Disorders of bone formation (osteomalacia)
  • Porous bones (osteoporosis)
12 to <20 Suboptimal care
20 to <50 Sufficient for bones and general health
≥50

Possible oversupply, with potential health consequences

Risk for:

  • Cardiac arrhythmias
  • Kidney stones
  • Oversupply of calcium

Source: RKI and Institute of Medicine