According to scientific research, it is clear that vitamin D performs several important actions. Beyond the known effect on calcium metabolism, and therefore on bone health, vitamin D also plays an essential role in modulating the immune system (Aranow et al, J Investig Med., 2012). A deficiency of vitamin D is connected to a greater risk of infection, but that's not all. In fact, as the latest research dedicated to the novel coronavirus is making it clear, vitamin D would also help to avoid an exaggerated reaction of the immune system, also a condition that should be avoided due to its severe effects. In fact, as has been observed in case of the novel coronavirus, if the virus passes the first defenses of the upper airways and reaches the lungs, it may happen that an overwork of the immune response triggers what is called a cytokine storm able to cause serious damage to the lungs, the real problem when we speak about complications induced by novel coronavirus (Ilie et al, Aging Clin Exp Res, 2020). Vitamin D seems able to avoid the overwork of the immune system and the connected consequences. But an adequate supply of vitamin D has proven useful in reducing the risk also of other viral forms such as influenza (Grant et al, Nutrients, 2020). We know that one of the most powerful natural sources of vitamin D is the sun. In fact, the skin produces vitamin D when exposed to sunlight. However, this is not always possible, for example, in winter we have less chance of sun exposure. Supplements are an alternative but you should always ask your doctor for advice to evaluate your personal situation and avoid interactions with the medications you are taking. But diet is also a valid source of vitamin D. Let's see the main foods that bring this very important vitamin.
Vitamin D, food sources
The data are obtained from databases dedicated to the topic, such as the FDA Database, and from the scientific literature (O'Mahony et al, Nutrients, 2011). The numbers shown in brackets are the quantity of vitamin D expressed in micrograms per 100 grams of product. Fish is an excellent source of vitamin D, in particular, cod liver oil (210-250), wild salmon (13-24), herring (5-15), mackerel (9-16), anchovies in oil (2-3). From the point of view of their intake of vitamin D, mushrooms should also be taken into consideration, we can mention winter mushrooms (13.6-30), shiitake (0.4), but also champignons (0.2). As for milk and dairy products, milk provides vitamin D (0.1), as well as yogurt (0.1), cheeses, for example cheddar (0.6) and butter (1.8). Finally, not to forget the eggs, in fact, the egg yolk is a source of vitamin D (4,9-5).
Vitamin D, daily intake
According to a report by the American National Academy of Medicine, the daily intake of vitamin D should be, for children older than one year and adults, 15 micro grams per day, for the elderly 20 micro grams per day (O'Mahony et al, Nutrients, 2011).