The pale spring sun has begun to appear in the sky, revealing unwashed windows and dust in the corners. But we'll have to wait a little while before the rays allow us to produce our own vitamin D.
"In April and May, the sun is high enough that we can produce it again," says Hanna Augustin, professor of nutrition at the University of Gothenburg.
Skeleton and muscles
Vitamin D is necessary, among other things, to regulate the body's calcium and phosphate balance. It is needed for the bones, muscles and immune system. When the sun's UVB rays hit the skin, vitamin D is produced from a precursor. However, because UVB rays are filtered out in the atmosphere when the sun is low, it is only during the summer months that the body can produce it.
For now, you need to head further south for the sun's rays to be strong enough, but depending on where in the country you live, it will soon be the start of the season. In central and southern Sweden, the sun is high enough from April, and in the northern parts it is in May. And there is no minimum time needed to get production started.
During the summer, it's enough to be outside for about 15 minutes a day and let the sun hit your skin, says Hanna Augustin.
Can be stored
We have to take advantage because as early as September-October the sun will be so low again that it cannot produce vitamin D.
But vitamin D is fat-soluble, which means we can store it for a while. At the population level, levels drop again around November, and then the contribution from diet becomes especially important, she says.
Many people do not need to take vitamin D supplements even during the winter. Eating a varied diet goes a long way. Fatty fish such as salmon and herring are examples of foods rich in vitamin D. In Sweden, foods such as milk and other dairy products, as well as plant-based drinks, are also fortified with vitamin D.
But those who don't eat these foods and aren't exposed to the sun may need supplements. The same applies to certain groups such as young children and the elderly, says Hanna Augustin.
Petra Hedbom/TT
Facts: Vitamin D
TT
Facts: Vitamin D
For some, it is difficult to get the daily requirement of vitamin D through food. The Swedish National Food Agency recommends vitamin D supplements for certain groups. This applies to young children and the elderly, but also to those who do not eat certain foods and/or do not get sun.
Anyone who needs to take vitamin D supplements should be careful not to take too high a dose.
The upper limit is:
infants 0–6 months: 25 micrograms per day
infants 7–11 months: 35 micrograms per day
children 1–10 years: 50 micrograms per day
adults and children from 11 years: 100 micrograms per day
How long a person needs to be in the sun to produce vitamin D depends on pigmentation. People with naturally darker skin need more time, and people with lighter skin need less time to achieve optimal vitamin D production.
Source: Swedish National Food Agency, Swedish Radiation Protection Authority
