Vitamin D is not only an essential vitamin but is also a hormone-like substance, which affects the immune system.

Why do we need vitamin D?

Vitamin D is found naturally in some foods and in supplements. However, the most common source of vitamin D is sunlight – around 90 percent of the body’s vitamin D actually comes from the sun. It is, however, not sunlight itself that contains vitamin D. Sunlight rather converts the cholesterol in the skin into vitamin D, which can then be stored in the body for future use. This conversion and storage requires sufficient exposure to sunlight, however, and the sun’s UVB rays must make contact with the skin, which only happens when the sun is at an angle of at least 45 degrees above the horizon. In the Nordic countries, the sun is only high enough for this to occur during summer time, (May-August) and even then only for a couple of hours in the middle of the day.

As previously mentioned, vitamin D is stored in the body during the summer months. However, vitamin D has a half-life of six weeks. So the supply of vitamin D therefore gradually decreases from about August/September onwards. For us northerners, it is therefore extra important to keep track of our vitamin D intake by reviewing our diets or supplementing with dietary supplements if necessary.

Some of the functions of vitamin D in the body

• The skeleton: Vitamin D promotes the storage of calcium, phosphate and magnesium in the skeleton. Which helps maintain a normal bone structure and normal calcium levels in the blood.
• Immune system: Vitamin D contributes to the normal functioning of the immune system. In countries with little sunlight where low levels of vitamin D are common, diseases such as MS, diabetes and rheumatism are more common than in countries that are closer to the equator, where sunlight is plentiful.
• Cell division: Vitamin D is an important component in cell formation. Healthy and well-functioning cell formation is an important part of cancer prevention.
• Muscle function: Vitamin D helps maintain normal muscle function. Vitamin D deficiency can manifest itself in the form of muscle fatigue and weakness as well as muscle pain.

Symptoms of vitamin D deficiency

Severe vitamin D deficiency can result in a soft and deformed skeleton, which is also called “rickets” when it occurs in children. This is, however, relatively uncommon nowadays. Even if you do not suffer from an outright vitamin D deficiency, many people have low levels of vitamin D, and there are also studies that have shown that this can affect your general health.

Some signs that you have insufficient levels of vitamin D in the body are:

• Fatigue and depression (especially in the spring when vitamin D stores begin to run out)
• Frequent infections and colds
• Sleeping problems
• Pains, weakness and muscle fatigue
• Inflamed gums

There are also so-called risk factors that increase the likelihood of suffering from vitamin D deficiency. These are: living in the Nordic countries, wearing full-coverage clothing all year round, eating a mainly vegan diet, spending a lot of time indoors, obesity, malabsorption diseases such as celiac disease and Crohn’s disease.

Sources of vitamin D

1. Sunlight: During the summer months, being outdoors in the sun in shorts and a T-shirt for about 15 minutes a day a couple of times a week, results in a sufficient intake of vitamin D. The body can only convert a limited amount of vitamin D at a time and for no longer than about 30 minutes at a time. Vitamin D uptake is also affected by skin colour (the darker the skin, the longer you need to be out in the sun to absorb the same amount of vitamin D), lifestyle, age, sun protection factor and time of day.

2. Diet: It’s difficult to get all the vitamin D you require from your diet alone. Diet should rather be considered a complement to sun exposure. There are two types of dietary vitamin D; D3 and D2. D3 is what your skin produces when you’re out in the sun. D3 is also found in animal foods such as oily fish and fortified dairy products. D2 is not as effective as D3, and is mainly found in various fungi such as chanterelles and porcini mushrooms.

3. Supplements: For people who avoid eating animal products or who, for whatever reason, do not get enough vitamin D through sunlight exposure or diet, supplements are a good solution. The recommended dose of vitamin D varies between 1000-5000 IU per day depending on the source.

Improve your ability to absorb vitamin D

All essential vitamins and minerals work together and are dependent on each other. To optimise the absorption of vitamin D, it is therefore important to have sufficient levels of vitamin K2 and magnesium in the body. Magnesium increases the uptake of calcium, while calcium releases vitamin D into the bloodstream. Vitamin K2, in turn, helps introduce vitamin D into the skeleton. Because vitamin D is also fat-soluble, it should always be taken along with a fat source.

References:

http://www.lakartidningen.se/Functions/OldArticleView.aspx?articleId=6279

https://www.ncbi.nlm.nih.gov/pubmed/20824663

https://www.ncbi.nlm.nih.gov/pubmed/30344276

https://www.vetenskaphalsa.se/solljus-kan-minska-risken-for-diabetes

https://www.vetenskaphalsa.se/d-vitaminbrist-kan-bidra-till-manga-sjukdomar/

The National Food Administration