Vitamin A (Retinol): Stiefkind der Ernährungsmedizin

Zusammenfassung

Wer kennt es nicht, das Bild der Karotte – symbolisch für die wichtige Vitamin-A-Zufuhr. Vitamin A spielt vor allem bei der Entwicklung des Gehirns und der Sehfähigkeit eine zentrale Rolle. Leider existiert auch in der heutigen Zeit immer noch das Problem, dass die Empfehlungen für eine bedarfsgerechte Vitamin-A-Zufuhr über die Ernährung nicht erreicht werden – mindestens 25 % der Bevölkerung leiden unter Vitamin-A-Mangel. Zu den Risikogruppen gehören insbesondere Kleinkinder, Schwangere und Stillende. Der Mangel kann zu erheblichen Beeinträchtigungen und Erkrankungen führen. Mittlerweile zeigen aktuelle Daten, dass die Bildung von Vitamin A aus Carotinoiden jedoch überschätzt wurde, d. h. die Fachgesellschaften sollten ihre Empfehlungen anpassen. Des Weiteren geht der Beitrag auf Vitamin A als Behandlungsoption bei COVID-19 ein.

Abstract

Vitamin A (retinol) is the most important vitamin for the mucosal immunity of the respiratory tract, the gastrointestinal tract, and the urogenital tract. National Surveys on vitamin A (retinol) intake for Germany indicate that at least 25 % of the population do not achieve the recommended daily requirement in their diet. The percentage may even be higher, as the previous nutritional surveys (e. g. NVS) used a conversion factor of 6:1 (6 mg beta carotene = 1 mg retinol) to calculate the vitamin A activity from the beta carotene (provitamin A) intake. A more realistic conversion factor seems to be 36:1 (36 mg beta carotene = 1 mg retinol). In gene transcription, the receptors for vitamin D (VDR) and vitamin A (RXR) merge, so that the actual effect of 1,25(OH)2D often occurs in combination with retinoic acid (RA) (e. g. adaptive immunity). Risk groups for an inadequate intake of vitamin A include elderly people, young children, pregnant women, breast-feeding mothers, and patients, as all these groups have increased requirements.

Schlüsselwörter

Vitamin A - Retinol - Retinsäure - COVID-19 - Hirnentwicklung - Carotinoide

Key words

Vitamin A - retinol - retinoic acid - COVID-19 - brain development - carotenoids

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