Vitamin D: What is it and how do you recognize a deficiency?

Vitamin D is an important, well-known vitamin (hormone) that many people are deficient in. In this article, you'll learn about the benefits of vitamin D, how to recognize a deficiency, and how to prevent it.

You will also learn which foods contain the most vitamin D and which supplements are suitable for various situations.

Vitamin D is called a fat-soluble vitamin, but it's officially a hormone. The body can produce it itself with the help of sunlight.

You can also get it from certain foods (oily fish, eggs, cheese, butter), but only to a limited extent. Vitamin D plays an important role in the body, including supporting bone health and the immune system.

Research shows that 9 out of 10 people in the Netherlands do not get enough vitamin D[1]

Vitamins are important supplements for various bodily functions. These are listed below.

Vitamin D…

1. Contributes to normal calcium levels in the blood
2. Supports normal growth and development of children's bones
3. Contributes to the maintenance of normal bones
4. Contributes to the normal absorption of calcium and phosphorus
5. Plays a role in the cell division process
6. Contributes to the normal functioning of the immune system
7. Contributes to the maintenance of normal teeth
8. Helps to reduce the risk of falls associated with postural instability and muscle weakness
9. Contributes to normal muscle function

Vitamin D2 and vitamin D3 are the most common forms of vitamin D in supplements.

• Vitamin D3 (cholecalciferol) - This form is naturally produced in the skin when exposed to sunlight and is often used in supplements because of its efficiency and effectiveness in increasing vitamin D levels in the blood.
• Vitamin D2 (ergocalciferol) – This form is produced in plants and fungi when exposed to UV light. It is often used in fortified foods and some supplements, but is generally considered less effective than vitamin D3.

Vitamin D3 also works best when dissolved in fat, as it is better absorbed. This product uses extra virgin olive oil for optimal absorption:

The amount of vitamin D you need varies by age and individual needs. However, there are guidelines for the daily amount.

To get enough vitamin D, it is important to spend enough time outside.

Incidentally, vitamin D3 isn't found in sunlight. Your body uses UVB rays from sunlight to produce vitamin D. So it works a little differently than you might think.

The strength of sunlight also plays a significant role in your vitamin D production. This also varies seasonally, so we've put together some tips to help you ensure you have sufficient vitamin D in your body throughout the year.

• Autumn and spring - 30 minutes of daily sunlight exposure between 11:00 AM and 3:00 PM, covering your hands and head, is often enough to produce sufficient vitamin D.
• Summer - sunlight is often very intense, making other times of the day (besides 11:00 AM - 3:00 PM) also ideal for producing sufficient vitamin D. Be careful not to burn during midday!
• Winter – it's (almost) impossible to produce enough vitamin D. The sunlight is too weak, and you often wear covering clothing, preventing sunlight from reaching your skin. A vitamin D supplement is necessary to prevent deficiencies.

When the skin is exposed to sunlight, especially UVB radiation, a process starts in the body that leads to the production of vitamin D3.

This process works as follows:

Step 1: UVB Ray Absorption - The skin absorbs the UVB rays from sunlight.

Step 2: Building block for vitamin D3 (7-dehydrocholesterol) is converted - The UVB radiation helps to convert the building block into previtamin D3, which is the precursor of vitamin D3.

Step 3: Formation of vitamin D3 - Previtamin D3 is unstable and is converted spontaneously into vitamin D3 (cholecalciferol) by the heat of the skin.

Step 4: Transport to the liver and kidneys - Here, vitamin D3 is converted into the active form (1,25-dihydroxyvitamin D3) so that it can be used in the body.

It's often thought that you can only get vitamin D from sunlight. However, this isn't the case, as food also contains vitamin D. Below are 20 important sources.

A vitamin D deficiency can occur, for example, in winter, when there's little sun. Certain age groups, such as the elderly, are also more likely to develop a deficiency. This can lead to various symptoms.

Some symptoms of a vitamin D deficiency are:

• Fatigue and weakness - A vitamin D deficiency can lead to general fatigue and weakness. People with a deficiency often feel lethargic and have less energy.
• Muscle pain and weakness - Vitamin D contributes to healthy muscle function. Muscle pain and weakness can therefore occur if you have a deficiency.
• Bone problems - Vitamin D contributes to calcium absorption and the maintenance of strong bones. A deficiency can therefore be detrimental to bone health.
• Reduced immunity - Vitamin D contributes to the normal functioning of the immune system. A weakened immune system is associated with reduced immunity.

Vitamin D3 also works best when dissolved in fat, as it is better absorbed. This product uses extra virgin olive oil for optimal absorption:

A vitamin D deficiency isn't acutely dangerous. However, it can negatively impact your health, as you've seen in the list above. Therefore, it's a good idea to address a deficiency. This can be done by spending more time in the sun or taking a supplement.

A vitamin D deficiency can have several causes. A lack of sunlight is an obvious one, but there are other reasons.

Let's start with this reason: you're not getting enough sunlight. This is the cause of the deficiency in most cases. Not getting enough sunlight can occur in winter or autumn, when the sunlight is less intense.

Another reason you might not get enough sunlight is that you always wear covering clothing or spend a lot of time indoors. Your body then can't produce the amount of vitamin D it needs.

If you don't get enough vitamin D from the sun, you could get it from food. See the table under "How do you get vitamin D from food?" If this doesn't happen, you'll still have a deficiency.

Dark or tinted skin produces less vitamin D than light skin. This is because the pigment in the skin blocks UV radiation. Therefore, much more sunlight is needed to produce vitamin D.

Magnesium plays an important role in the production of vitamin D [2]. Without magnesium, it's harder to produce vitamin D, so you need to get enough of it.

Overweight people are more likely to have a vitamin D deficiency [3] . Vitamin D is stored in fat. When a body has more fat, it also needs more vitamin D to maintain healthy levels.

Vitamin D is absorbed in the intestines when it comes from food. When this doesn't work properly due to intestinal conditions such as IBD[4], celiac disease (gluten allergy), or gastric bypass[5], this can lead to a deficiency.

A liver problem can cause a deficiency of the enzyme 25-hydroxylase. This is an enzyme that is necessary for the production of vitamin D[6].

Roughly the same applies to the kidneys. The kidneys normally produce the enzyme 1-alpha-hydroxylase. This enzyme is necessary for the production of vitamin D[7].

An excess of vitamin D can occur if you take too many vitamin D supplements for a long period of time. The tolerable upper limit of vitamin D is as follows[8].

However, these upper limits are still very low, because you really have to take 10 times this dose per day for months to get too much vitamin D.

Symptoms of too much vitamin D may include:

1. Calcium deposits in the body
2. Damage to the kidneys
3. Nausea
4. Decreased appetite
5. Fatigue

In principle, vitamin D3 is the best form to take as a supplement because it works more effectively. You also want a vitamin D supplement that's dissolved in fat for better absorption.

The best dosage and source of vitamin D depends on the individual situation and preferences. These are listed below.

Due to their age, older people are more likely to have a D deficiency. Therefore, vitamin D3 in 75 micrograms is the best option.

If you get enough time outside (at least 30 minutes a day between 11am and 3pm), we recommend a lower dose vitamin D3 supplement of 25 mcg.

If you're an adult looking for regular vitamin D support, 25 micrograms of vitamin D3 is a good option. This is the most common dosage for an average adult.

Personally, I take a 75 mcg capsule daily, as I am prone to vitamin D deficiency.

A daily dose of 25 mcg of vitamin D3 is also a good maintenance dose for children. Children should not exceed 50 mcg per day, so 25 mcg per day is an excellent maintenance dose.

If you prefer a slightly lower dosage, you can also choose to give your child a 25 mcg vitamin D capsule three times a week.

If you follow a vegetarian or vegan lifestyle, we recommend vegan vitamin D. We offer this in our webshop as vegan vitamin D3 in 25 micrograms.

Vegan vitamin D is extracted from algae and is therefore completely plant-based, making it suitable for vegetarians and vegans.

Sources

1. https://www.ivg-info.nl/nieuws/9-op-de-10-nederlanders-krijgt-te-weinig-vitamine-d-binnen/
2. https://pubmed.ncbi.nlm.nih.gov/29480918/
3. https://www.tandfonline.com/doi/full/10.1080/07315724.2018.1538828
4. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6566188/
5. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1570540
6. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5946281/
7. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5946281/
8. https://www.voedingscentrum.nl/encyclopedie/vitamine-d.aspx#blokhoeveel-vitamine-d-heb-je-per-dag-nodig