Vitamin D is a hormone-like vitamin that is very important for good overall health and strong, healthy bones. Vitamin D improves the absorption, transport, and utilization of calcium and phosphorus, which in turn are necessary for bone and tooth formation. It is also a factor in ensuring that your muscles, heart, and lungs function optimally.
Why do we need vitamin D?
Vitamin D plays an important role in the body's cell division process and contributes to the normal function of the immune system. Quite simply, it helps cells throughout the body communicate properly. People with an adequate level of vitamin D are generally much better equipped to fight colds and other illnesses.
How do we get vitamin D?
Vitamin D is mainly found in oily fish, wild mushrooms, and egg yolks. However, it is difficult to get sufficient amounts through the diet. If you are vegetarian or vegan, it is even more difficult.
Otherwise, vitamin D mainly comes from your skin when it is exposed to sunlight. Your body then undergoes a number of chemical processes to alter it so that your body can use it in the best possible way. However, the amount of vitamin D you get from sunlight depends on:
- The time of day – your skin produces more if you expose it around midday.
- Where you live – the closer you live to the equator, the easier it is for you to produce vitamin D from sunlight year-round. In the Nordic countries, we can only obtain vitamin D from the sun during the summer.
- Your skin tone – fair skin produces vitamin D faster than darker skin. For example, if you have very fair skin, it may take about 15 minutes to produce an adequate amount of vitamin D, whereas if you have dark skin, it may take up to 2 hours.
- The amount of skin you expose – the more skin you expose to the sun, the more vitamin D your body produces.
- Because the sun's rays are weaker and the days are shorter during autumn and winter in Sweden – and because we spend less time outdoors and wear more clothes – we in Sweden produce virtually no vitamin D from the sun between October and April. Therefore, a vitamin D supplement can be highly beneficial during this period.
Low levels of vitamin D can affect energy levels, mood, depression, the immune system, and more. One way to find out your exact needs is to measure vitamin D levels in your blood, either through a therapist, at a healthcare centre, or privately through, for example, Werlabs or Blodkollen.
Vitamin D supplements
Vitamin D comes in two forms: D2 and D3.
Both have been shown to be effective in clinical studies for raising vitamin D levels in the blood, but vitamin D3 is preferable because it is utilized much more effectively by the body and is the form that comes from natural sources: the sun and our food.
Vitamin D3 can be extracted in various ways, and today there are primarily two natural sources used in supplements: sheep's wool or lichen. Both are effective and good sources of active vitamin D3, and which one you choose is entirely up to you. The one from lichen is 100% plant-based, which may be an advantage for many people.
One vitamin that may be beneficial to combine with D3 is vitamin K, which is also fat-soluble and works synergistically with vitamin D to build strong bones, as well as being important for the blood's ability to clot.
How much vitamin D do we need?
The best way to find out exactly how much vitamin D you need is to take a supplement for a couple of months and then have a blood test. The absorption of vitamin D supplements varies from person to person and is affected by several factors. Therefore, it is impossible to give a recommendation that applies to everyone.
The test is called 25-OH-D and can be ordered through a healthcare centre or private laboratory.
For most people, the optimal goal is a blood level of 50–80 ng/ml or 125–200 nmol/L (there are two different ways to express vitamin D measurements. In Sweden, ng/ml is the most common).
That said, we recommend these doses as a starting point during the winter months in the Nordic countries:
Adults: 1000–2500 IU daily (alternatively 5000 IU every other day).
Children under 12: 500–1000 IU daily.
