Which foods contain vitamins D and A.

Selected questions and answers about vitamin D.

Joint FAQ of the BfR, the DGE and the MRI of October 22, 2012

Vitamin D promotes the absorption of calcium from the gastrointestinal tract and the hardening of the bones. It influences muscle strength, regulates calcium and phosphate metabolism and is also involved in other metabolic processes in the body. In humans, vitamin D is formed in the skin under the influence of sunlight. In contrast to the body's own production, the supply of vitamin D through the diet only accounts for a relatively small proportion of the vitamin D supply. The German Society for Nutrition e. V. (DGE) offers 20 micrograms of vitamin D per day for children, adolescents and adults. This value applies in the absence of the body's own education.

A general fortification of foods with vitamin D is not recommended. The focus is on the body's own production of vitamin D and thus the recommendation to produce and store vitamin D by exposing the skin to sunlight. The body's own production varies from person to person and is dependent on other factors, such as the latitude and the time of year. It is recommended that you expose yourself to the sun for a total of 5 to 25 minutes a day with your face, hands and larger parts of arms and legs uncovered. The intake of vitamin D supplements is only recommended if a targeted improvement in supply, especially for risk groups, cannot be achieved either through diet or through the body's own vitamin D production through exposure to the sun.

The BfR, DGE and MRI have summarized frequently asked questions and answers about vitamin D below.

1. What is vitamin D and why does the body need vitamin D?

Vitamin D has a special position among the vitamins. In contrast to other vitamins, vitamin D can itself be formed from precursors that are present in the body. The body's own production takes place when the skin is exposed to sunlight (UVB light exposure) and, compared to the supply of vitamin D through food, makes a significantly greater contribution to the supply of this vitamin to humans. Vitamin D regulates the calcium and phosphate metabolism and thereby promotes the hardening of the bones. Vitamin D is also involved in other metabolic processes in the body and also has an influence on muscle strength.

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2. How much vitamin D does a person need and how can one determine the vitamin D supply?

The reference value for vitamin D intake is 20 micrograms per day if the body does not produce it naturally. This estimate, derived from studies by the DGE, applies to all age groups from one year of life. If you stay outdoors regularly, under normal living conditions in this country, the body's own (endogenous) formation in the skin contributes 80 to 90 percent to the vitamin D supply.

In contrast, the vitamin D intake through the diet with the usual foods only accounts for a relatively small proportion (10 to 20 percent) of the vitamin D supply. Therefore, their detection is not suitable for assessing the actual supply status. The concentration of 25-hydroxyvitamin D in the blood serum is used as a marker for assessing the supply, because this reflects the vitamin D supply via the diet and the body's own vitamin D production.

One speaks of a vitamin D deficiency at serum concentrations of the marker 25-hydroxyvitamin-D below 30 nanomoles per liter of serum (30 nmol / l). This corresponds to 12 nanograms per milliliter of serum (12 ng / ml). A good vitamin D supply with regard to bone health is when the blood concentration of this marker is at least 50 nanomoles per liter of serum. This corresponds to 20 nanograms per milliliter. If the body does not produce its own vitamin D, this concentration is achieved with an intake of 20 micrograms of vitamin D per day.

Since a large part of the healthy German population cannot be assumed to have a vitamin D deficiency, the vitamin D supply should only be determined if there is justified suspicion of a deficiency or in persons at risk.

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3. How is the vitamin D supply of the German population? Is there a supply gap?

The majority of the population is not deficient in vitamin D. However, almost 60 percent of German citizens do not achieve the desirable blood concentration of the marker 25-hydroxyvitamin-D of 50 nanomoles per liter. This means that a large proportion of the population does not use the preventive potential of vitamin D for bone health and is therefore not adequately supplied.

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4. How much sun does the body need to produce enough vitamin D through the body's own production? How is it in autumn and winter compared to summer?

The body's own vitamin D production in the skin through sunlight (UVB rays) depends on latitude, time of year and time of day, weather, clothing, length of stay outdoors and skin type and also the use of sunscreens, which reduce the body's own production. This means that the contribution made by the body's own production to vitamin D supply can vary greatly from person to person. Thus, the body's contribution to vitamin D supply cannot be quantified either for individuals or in general for the general population.

In the summer months it is possible to achieve the desired serum concentration of 25-hydroxyvitamin-D of 50 nmol / l through the body's own production. The body's own production through exposure to sunlight depends on the geographic location. The following table gives orientation values ​​for the duration of sun exposure for a good vitamin D supply for latitudes 50 to 75 N °.

Accordingly, in Germany, which extends from latitude 47 to 55 N °, it is sufficient for about half of the year for adults, a quarter of the body surface (face, hands and parts of arms and legs) between 12 and 3 p.m. Expose to the sun for 5 to 25 minutes depending on skin type and time of year.

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Duration of exposure to sunlight for skin types I / II (light to very light skin color, light red or blond hair, blue or green eyes)Duration of sunlight exposure for skin type III (medium skin tone, dark hair, brown eyes)
March to May10 to 20 minutes15 to 25 minutes
June to August5 to 10 minutes10 to 15 minutes
September to October10 to 20 minutes15 to 25 minutes

In the morning from 10 a.m. to 12 p.m. and in the afternoon from 3 p.m. to 6 p.m., the duration of sunlight exposure can be doubled.

In contrast to the summer months, solar radiation in Germany in the months from October to March is not strong enough to ensure adequate vitamin D production. However, vitamin D can be stored in the body. These stores contribute to the vitamin D supply in winter. The storage tanks, which have been reduced over the winter months, can then be replenished from spring onwards.

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5. How is the storage capacity for vitamin D in the organism?

Vitamin D is mainly stored in the fat and muscle tissue of the human body; smaller amounts are also found in the liver. Overall, the storage capacity is relatively large and contributes to the vitamin D supply in winter.

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6. How much vitamin D is there in food?

There are only a few foods, mostly of animal origin, that contain vitamin D in significant quantities. These include in particular fatty fish (e.g. salmon, herring, mackerel) and, to a much lesser extent, liver, margarine (enriched with vitamin D), egg yolks and some edible mushrooms. In Germany, we only supply 2 to 4 micrograms of vitamin D per day through a diet with the usual foods.

FoodVitamin D (micrograms per 100 grams)
herring7,80 – 25,00
salmon16,00
Chicken egg yolk5,60
mackerel4,00
Chicken egg, total2,90
margarine2,5 – 7,5*
Chanterelles2,10
Mushrooms1,90
Beef liver1,70
Gouda cheese, 45% F. i. Tr.1,30
butter1,20
Veal liver0,33
Whole milk, 3.5% fat0,09
*Exemptions for up to 7.5 micrograms per 100 grams have been granted

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7. What are the consequences of a vitamin D deficiency?

With a vitamin D deficiency in infancy and childhood, the bones are insufficiently mineralized, they remain soft and can become deformed (rickets). Bone metabolism disorders can also occur in adulthood. Demineralization of the bone can make the bones soft (osteomalacia). A vitamin D deficiency can contribute to the development of osteoporosis, especially in old age. An actual deficiency in vitamin D with clinical symptoms must be distinguished from the condition of an inadequate vitamin D supply, in which the preventive potential of this vitamin for bone health is not adequately used. This means that the benefits of adequate vitamin D supply - reducing the risk of falls and bone fractures in older people - are not realized.

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8. Which risk groups are there for a vitamin D deficiency?

The risk groups for an undersupply include people who can hardly or not at all be outdoors or - for cultural or religious reasons, for example - only go outside with their bodies completely covered. In addition, the risk groups include people with a dark skin color (high melanin content), as they can produce less vitamin D than people with light skin. Elderly people are another important risk group, as vitamin D formation decreases significantly with age and there are also chronically ill people with restricted mobility, chronically ill people in need of care who are barely or not at all outdoors in the elderly. In addition, infants are among the risk groups for a vitamin D deficiency because, on the one hand, the vitamin D content of breast milk is very low and, on the other hand, infants should not be exposed to direct sunlight, as their skin's own protective mechanism has yet to develop .

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9. Is the body's own vitamin D production sufficient in old age?

In old age, the skin's ability to produce vitamin D decreases significantly and can be reduced to less than half compared to younger people. If, in addition, less time is spent outdoors in old age and the skin's exposure to sunlight is restricted, the body's own vitamin D production also decreases. This is particularly the case with elderly people with restricted mobility, chronically ill and in need of care (nursing home residents, geriatric patients). They are often diagnosed with a vitamin D deficiency. This generally does not apply to (older) people who spend a lot of time outdoors.

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10. Should you go to the solarium to improve your vitamin D supply?

It does not make sense to go to a solarium to improve the vitamin D supply.

According to a recommendation by the Federal Office for Radiation Protection, children and young people in particular should not go to the solarium. According to the Federal Office for Radiation Protection, visits to tanning beds can increase the risk of skin cancer.

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11. Is an oversupply of vitamin D possible through the body's own synthesis?

Vitamin D overdoses and the associated adverse effects are only possible through excessive oral intake (permanently> 100 micrograms per day) and not through excessive exposure to the sun.

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12. What should you watch out for in the event of frequent exposure to the sun?

Too much sunlight increases the risk of developing skin cancer. Therefore, frequent and intensive sun exposure in summer at lunchtime (in accordance with the recommendations of the German Cancer Aid) is not recommended. A recommendation to avoid the sun is not useful or necessary. So outdoor physical activity is highly recommended; but sunburn should definitely be avoided by taking appropriate measures.

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13. Is it necessary to use foods fortified with vitamin D or vitamin D supplements?

Fortifying foods with vitamin D is not recommended. The focus is on the body's own production of vitamin D and thus the recommendation to produce vitamin D through sun exposure of the skin. The intake of vitamin D supplements (i.e. an additional intake beyond the diet) is only recommended if insufficient supply has been proven and if there is a targeted improvement in supply, neither through diet nor through the body's own vitamin D production can be achieved by exposure to sunlight. These risk groups include:

People who are hardly or not at all or only with their bodies fully covered outdoors or people with dark skin color. Those who do not go out into the sun regularly and regularly include, in particular, the elderly with restricted mobility, the chronically ill and in need of care (nursing home residents, geriatric patients, seniors at risk of osteoporosis and falls). In these groups of people there are comparatively more serious states of undersupply or deficiency in vitamin D that require treatment. In addition, the ability of the skin to produce vitamin D decreases significantly with age and the body's own contribution to vitamin D supply in addition, it sinks if the stay in the sun is insufficient. In the case of breastfed and non-breastfed infants, a vitamin D tablet is given to prevent rickets from the first week of life until the end of the first year of life.

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14. Does a vitamin D oversupply have health consequences?

Vitamin D overdoses and the resulting possible side effects are not possible through excessive exposure to the sun, but only through excessive oral intake.

In the case of additional intake of vitamin D via vitamin D preparations, it must be taken into account that the European Food Safety Authority (EFSA) has a tolerable total daily intake of 100 micrograms of vitamin D for adults and children aged 11 and over and for children up to 10 years of age Years of life derived from 50 micrograms of vitamin D. These tolerable total daily intake amounts refer to the vitamin D intake from all foods (including vitamin D supplements and fortified foods).

With a regular daily intake of more than 100 micrograms of vitamin D, which with normal eating habits is currently only possible through excessive intake of vitamin D supplements, undesirable effects such as the formation of kidney stones or kidney calcification can occur. For medical reasons, however, higher amounts of vitamin D may be medically indicated.

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15. Does taking vitamin D supplements protect against cancer or other diseases?

The current data confirms that a good supply of vitamin D in the elderly can reduce the risk of falls, broken bones, loss of strength, loss of mobility and balance, and premature death. On the other hand, there is no high level of evidence that vitamin D reduces the risk of cancer, cardiovascular disease or type 2 diabetes mellitus.

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16. What can consumers do?

Consumers should go out into the fresh air often in both summer and winter. Exercise and outdoor activity, as well as exercise, strengthen muscles and bones. It is recommended to consume fatty sea fish, which contains vitamin D as well as n-3 fatty acids and iodine, once or twice a week. A good supply of vitamin D can be achieved without taking vitamin D supplements if the skin is sufficiently exposed to the open air and the skin is exposed to the sun, as well as a balanced diet.

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