Demnach reicht es auch in Deutschland, das sich von Breitengrad 47 bis 55 N° erstreckt, für ungefähr die Hälfte des Jahres für Erwachsene aus, pro Tag ein Viertel der Körperoberfläche (Gesicht, Hände und Teile von Armen und Beinen) je nach Hauttyp und Jahreszeit 5 bis 25 Minuten der Sonne auszusetzen.

Quelle: http://www.bfr.bund.de/de/ausgewaehlte_fragen_und_antworten_zu_vitamin_d-131898.html

Mehr als 100μg/Tag sollten nicht eingenommen werden. Quelle: https://www.netdoktor.de/ernaehrung/vitamin-d/ueberdosierung/

Im Falle der zusätzlichen Aufnahme von Vitamin D über Vitamin D-Präparate ist zu berücksichtigen, dass die Europäische Behörde für Lebensmittelsicherheit (EFSA) für Erwachsene und für Kinder ab 11 Lebensjahren eine tolerierbare Gesamtzufuhrmenge pro Tag von 100 Mikrogramm Vita­min D und für Kinder bis 10 Lebensjahre von 50 Mikrogramm Vitamin D abgeleitet hat.

Quelle: http://www.bfr.bund.de/de/ausgewaehlte_fragen_und_antworten_zu_vitamin_d-131898.html

Die Deutsche Gesellschaft für Ernährung empfiehlt die Einnahme von 20μg/Tag Vitamin D ab dem ersten Lebensjahr. Das schließt Vitamin D aus normaler Nahrung bereits ein.

Quelle: http://www.dge.de/wissenschaft/referenzwerte/vitamin-d/

Das Scientific Advisory Committee on Nutrition hat 2016 folgende Empfehlung herausgegeben:

SACN Vitamin D And Health Report 2016.pdf

Original: https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/537616/SACN_Vitamin_D_and_Health_report.pdf

Altersunabhängig ab Geburt 10μg/Tag Vitamin D Einnahme in Wintermonaten (Oktober bis März).

• RNI = Reference Nutrient Intakes
• DRV = Dietary Reference Values
• RCT = randomised controlled trial

The small amount of UVB radiation in winter sunlight is insufficient to initiate synthesis of any biologically relevant amounts of vitamin D.

Sunlight-induced vitamin D synthesis in white-skinned populations becomes effective from late March/early April with maximum concentrations observed in September after a summer of exposure. Serum 25(OH)D concentration decreases from October onwards throughout the winter months.

The pigment melanin absorbs so me of the UVB radiation which would otherwise be absorbed by 7-DHC. This means that if the absolute dose of UVB radiation is the same as that given to a person with white skin then people with dark skin will synthesise less. However, darker skin has the same capacity to synthesise vitamin D if the dose of radiation is adjusted for the protective effect of melanin.

Cohort studies suggest an association between increased serum 25(OH)D concentration and decreased fracture risk in adults ≥50y; evidence from RCTs, however, suggests vitamin D plus calcium supplementation is more effective than vitamin D alone in reducing fracture risk. On balance, vitamin D supplements alone appear to have no effect on fracture risk in older men and women.

Evidence from RCTs suggest that vitamin D supplementation may improve muscle strength and function in adults <50y with mean serum 25(OH)D concentration <30nmol/L.

Previously in the UK, an RNI (but not an EAR or LRNI) for vitamin D was set only for population groups at high risk of deficiency (DH, 1991). It was assumed that, for most people, the amount of vitamin D produced by exposure to sunlight containing UVB in the summer months would be adequate for achieving serum 25(OH)D concentrations ≥25nmol/L during winter. It is now known that this is not the case.

An RNI of 10μg/d (400IU/d) is recommended for the general UK population aged 11y and above.
…
This is the average amount needed to achieve a serum 25(OH)D concentration ≥25nmol/L during winter in 97.5% of the population.

Data from the modelling exercise were therefore extrapolated to younger age groups and the RNI of 10μg/d (400IU) recommended for the UK population was considered appropriate for children aged 4 up to 11y.

Since data are not available to clearly relate serum 25(OH)D concentration in the infant to current or long term health, Safe Intakes rather than RNIs are recommended for infants and children aged up to 4y.

Safe Intakes are based on a precautionary approach and reflect the insecurities of the data.

A Safe Intake range of 8.5-10μg/d (340-400 IU), based on concentrations of vitamin D in infant formula, is recommended for infants aged 0-11m.

There is currently no vitamin D RNI for exclusively breastfed infants because it was previously assumed that maternal vitamin D supplementation during pregnancy and then breast milk would provide the infant with adequate vitamin D for the period of exclusive breast feeding. The few available data suggest that it is unlikely that an exclusively breastfed infant in the UK would maintain a serum 25(OH)D concentration ≥25nmol/L for 6 months. Therefore the Safe Intake range of 8.5-10μg/d (340-400IU) is recommended for all infants, including those who are exclusively breast fed and those who are breastfed and part-formula-fed, from birth.

A Safe Intake of 10μg/d (400IU), based on the RNI for the UK population, is recommended for infants and children aged 1-3y.