Vitamin D

Briefly about vitamin D3

• Formed in our skin with the help of sunlight and it is almost impossible to get enough in Sweden during most of the year
• The amount of vitamin D most people get through food is negligible (also basically non-existent in a vegetarian diet)
• According to many researchers, the existing daily reference intake (DRI) is too low

Learn more about vitamin D

Vitamin D3 is produced in our skin with the help of sunlight. Vitamin D is a fat-soluble vitamin and is stored in body fat. In regions with low sun exposure for a significant part of the year, our skin does not receive enough sunlight. Therefore, supplementation of D3 is often needed, at least from September to April. Many people today have a deficiency of vitamin D, and here are some reasons for it:

Higher levels are needed than the recommended daily intake (RDI) to strengthen the immune system and more.

Limited sun exposure and low sun angle in regions with higher latitudes.

Covering clothing that blocks sunlight. Sunscreen filters out UV light.

Hospital patients and residents of institutions spend time indoors and may have poor diets.

Elderly individuals produce less vitamin D in their skin.

Foods with low levels of vitamin D.

Obesity can impair vitamin D absorption.

Individuals with darker skin require more sunlight for vitamin D production.

Magnesium deficiency can prevent the activation of vitamin D3 into its active form.

What is vitamin D good for?

Vitamin D3 has many important functions in the body, and perhaps the most well-known is its role in increasing calcium absorption, thereby contributing to strong bones and teeth. However, it is also crucial for a strong immune system, cell growth, and cellular function. It plays a role in the body’s energy metabolism by participating in the production of the hormone thyroxine in the thyroid gland. Providing supplements to the elderly and immunocompromised groups can be an important measure to support a stronger immune system.

What can a lack of vitamin D mean?

Vitamin D deficiency can cause various symptoms and conditions, including weak bones and teeth, as well as other health issues. Some of the common symptoms of vitamin D deficiency include weakened immune system, fatigue, depression, numbness in the arms and legs, muscle pain and cramps, and general skeletal and joint pain. In children, severe vitamin D deficiency can lead to a condition called rickets, characterized by soft and deformed bones. In adults, long-term deficiency can result in a condition known as osteomalacia, which is characterized by softening of the bones. It is important to maintain adequate levels of vitamin D to prevent these complications and support overall health.

How do we get vitamin D?

• The body’s own production in the skin via the sun
• Via food – Vitamin D3 is found in certain animal foods, for example in fatty fish such as salmon, in egg yolks, fortified milk products and D2 can be found in plants and mushrooms.
• Via vitamin supplements – like D3 or D2.

Vitamin D: In-depth

D-vitamin is a fat-soluble vitamin that is primarily known as the “sunshine vitamin” because it is synthesized in our skin through exposure to UV rays from the sun. It is involved in calcium metabolism and severe deficiency of vitamin D can lead to a condition called rickets. However, rickets is just the tip of the iceberg when it comes to vitamin D deficiency. Recent research on the functions of vitamin D suggests that the recommended levels are often too low to achieve sufficient plasma levels, especially in regions where sunlight is limited for a significant part of the year.

D-vitamin is more than just a vitamin and is now classified as a steroid hormone because our bodies can produce it under the right conditions.

In recent years, there has been a lot of discussion about the relationship between vitamin D and the immune system. In addition to its role in mineral metabolism, vitamin D has various important functions in the body, particularly for the immune system. It has also been found to have protective effects against cancer, cardiovascular diseases, and many autoimmune diseases.

High doses of vitamin D supplements have been shown to protect against viral infections and serious respiratory infections such as pneumonia. It also helps protect against severe cytokine storms. Providing supplements to the elderly and immunocompromised groups can be a cost-effective preventive measure.

Approximately 80% of our vitamin D (excluding supplements) is produced in the skin. In regions with limited sunlight, it can be challenging to obtain sufficient amounts of vitamin D. During the summer months, we need to build up a reserve of vitamin D to sustain us during the winter months when the sun is low, we wear covering clothing, and most people spend less time outdoors.

As we age, our ability to produce vitamin D in the skin decreases. Obesity also impairs the body’s ability to utilize vitamin D effectively.

Elderly individuals residing in nursing homes or hospitals often experience vitamin D deficiency.

To obtain sufficient vitamin D through diet alone, one must consume ample amounts of fatty fish, eggs, and fortified dairy products, which many people do not consume in adequate quantities today.

Receptors for D in most cells

Almost all cells have receptors for vitamin D, where vitamin D can bind and be taken into the cell. Recent research has shown that a large number of different cell types, apart from bone tissue, such as nerve cells, pancreatic cells, prostate cells, breast tissue, intestinal tissue, and various immune cells, have vitamin D receptors and are thus responsive to signals from vitamin D. This shows that vitamin D has many more functions in the body than just the “old” skeletal-related functions!

The metabolism of vitamin D

Most people are aware that vitamin D is produced in the skin when we are exposed to sunlight. All animals and plants can produce vitamin D when exposed to the sun’s ultraviolet B rays. When the sun hits the skin, a reaction occurs where the substance 7-dehydrocholesterol, present in the skin, is converted into vitamin D3 (cholecalciferol). This process takes place in the lower layers of the epidermis. Plants, especially fungi and lichens, can also produce large amounts of vitamin D, but in the form of vitamin D2 (ergocalciferol).

Afterwards, vitamins D3 and D2 need to be activated in the liver to form calcifediol, 25(OH)D (25-hydroxyvitamin D). This is the most common metabolite of circulating vitamin D, and most of it is bound to serum proteins in the blood. It is used as an indicator of the body’s vitamin D stores. 25(OH)D can be measured in serum through a blood test and is measured in nmol/liter. Calcifediol has a turnover time of 2-3 weeks. However, it is not the most physiologically active form; the vitamin needs to undergo another conversion in the kidneys to become fully active. In the kidneys, the final active form (1,25-dihydroxyvitamin D), the steroid hormone calcitriol, is produced.

So, what is the difference between a vitamin and a hormone? The definition of a hormone is that it is a substance produced by the body in one tissue/organ and has its effects on other places, in other cells, in the body, where it is transported through the bloodstream.

The definition of a vitamin is that it is an organic compound, an essential nutrient that is needed in certain amounts and must be obtained through food. Therefore, for example, vitamin C is not a vitamin for a horse, but rather a hormone.

Do we need to take vitamin D supplements?

The majority of people need to take additional supplements of vitamin D! According to recent research, supplementation of 4000 – 10000 IU/day is recommended to maintain optimal serum levels and achieve a well-functioning immune system.

It may be appropriate to regularly test vitamin D levels, for example, once a year, to ensure that the supplement dosage is adequate. The measurement typically done is the amount of calcifediol, 25-hydroxyvitamin D (25OH-D), in the serum. See below.

But why are supplements needed?

• Higher levels than the Recommended Daily Intake (RDI) are needed to strengthen the immune system, among other benefits. There is insufficient sunlight and the sun is low at our latitudes. Covering clothing reduces the exposure to sunlight. Sunscreen filters out UV rays. Hospital patients and institutionalized individuals spend time indoors and may have poor diets. Older individuals produce less vitamin D in the skin. Foods have low levels of vitamin D. Obesity impairs vitamin D absorption. Darker-skinned individuals have lower production in the skin and require more sun exposure. Magnesium deficiency prevents the activation of D3 into its active form.At our latitudes, the sun’s rays are not sufficient during the winter months, as it is too low for the angle of the sunlight to be sufficiently effective on the skin. The angle should be at least 45 degrees to provide adequate sun exposure to the skin. The highest angle reached by the sun’s rays (around midsummer) in Sweden is 58 degrees, and that is in southern Sweden. Therefore, from October to April, our own production of vitamin D is virtually nonexistent, and even September and April are considered “poor months.”It also requires us to be in the sun with bare skin. Depending on the type of work, most people do not spend much time in the sun except during vacations. If we encounter a rainy period, it can spoil this source of vitamin D. Applying sunscreen, which is recommended for protection against skin cancer, significantly reduces vitamin D production. Similarly, dark-skinned individuals living at our latitudes have greatly reduced production of vitamin D3 in the skin.

  Furthermore, older individuals, over 65-70 years, have a significantly reduced amount of 7-dehydrocholesterol in the skin, which is needed to produce vitamin D3. As a result, older individuals have a diminished capacity to produce D3 in the skin, possibly in combination with reduced sun exposure. Elderly individuals staying in hospitals or institutionalized settings have no or minimal opportunity to produce their own vitamin D, and the food they consume does not provide significant amounts. This results in the majority of older individuals having very low levels of D3 and requiring supplementation.

  Consuming fatty fish is not recommended too often due to the presence of environmental pollutants. Additionally, the most common type of fish consumed is farmed salmon, which contains only 20-25% of the amount of D3 found in wild-caught salmon. It would require large amounts of salmon, eggs, fortified milk, etc., to reach desirable serum levels, so in practice, few people obtain sufficient vitamin D through their diet.

What serum levels of D do we need?

According to current recommendations, serum levels below 25 nmol/liter of calcifediol (25(OH)D) are considered vitamin D deficiency, and insufficient levels range up to 75 nmol/liter.

However, recent research suggests that levels should ideally be between 100 and 150 nmol/liter to achieve optimal immune function.

To reach these higher serum levels, supplementation of 4000 to 10000 IU/day is recommended based on new research studies. Such high doses of vitamin D do not increase the risk of calcium deposition in blood vessels and other cells if vitamin K is consumed alongside vitamin D. Vitamin K helps to direct calcium storage in bone tissue, where it belongs. High calcium intake combined with low magnesium intake is considered the major culprit for calcium deposition in “wrong” cells.

It is advisable to monitor your vitamin D levels in the blood annually.

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