Introduction: Why is vitamin D so important for your health?
Vitamin D, also known as cholecalciferol or calciferol, is often called the “sunshine vitamin.” And for good reason: our bodies can produce this vitamin naturally under the influence of sunlight. Yet, millions of people worldwide suffer from vitamin D deficiency, which can lead to numerous health problems.
Vitamin D is essential for the absorption of calcium and phosphate, important building blocks for strong bones and teeth. It also supports muscle function, contributes to a healthy immune system, and can even influence your mood and energy levels.
In this ultimate guide, you’ll discover the benefits of vitamin D , which foods contain it, how to recognize a deficiency, which supplements you can use, and the recommended dosages for different age groups. We’ll also discuss vitamin D side effects , the differences between vitamin D and D3, and answer frequently asked questions.
Let’s start with the basics.
What is vitamin D?
Vitamin D is a fat-soluble vitamin and also functions as a hormone. It exists in two main forms:
- Vitamin D2 (ergocalciferol) : Mainly from plant sources and fortified foods.
- Vitamin D3 (cholecalciferol) : Produced in the skin by sunlight (UVB) and also found in animal products such as oily fish, eggs and liver.
Vitamin D3 is more effective at raising blood levels of vitamin D than D2, and is therefore often recommended in supplement form.
The crucial functions of vitamin D in the body
1. Bone health and calcium absorption
Vitamin D increases the absorption of calcium and phosphate from the intestines. Without enough vitamin D, your bones can weaken, which can lead to osteoporosis, osteomalacia (softening of the bones), or rickets in children.
Important for:
- Strong bones
- Healthy teeth
- Preventing bone fractures
2. Muscle function and fall prevention
Vitamin D supports muscle function. A deficiency can lead to muscle weakness and an increased risk of falls, especially in the elderly.
Important for:
- Balance and coordination
- Fall prevention
- Muscle recovery
3. Immune system and infection control
Vitamin D regulates the innate and adaptive immune response. People with low vitamin D levels are more susceptible to respiratory infections and other infectious diseases.
Important for:
- Resistance to viruses and bacteria
- Possible prevention of autoimmune diseases
- Faster healing
4. Cardiovascular health
There’s growing evidence that vitamin D can contribute to a healthy heart and blood vessels. Deficiencies are associated with an increased risk of high blood pressure and cardiovascular disease.
5. Mental health and mood
Low vitamin D is linked to depressive symptoms, seasonal affective disorder (winter depression) and lower energy levels.
Important for:
- Reducing fatigue
- Positive influence on mood
- Improvement of cognitive functions
How does the body produce vitamin D?
The body produces vitamin D in the skin under the influence of sunlight, particularly UVB radiation. Production depends on:
- The amount of sunlight
- The latitude where you live
- The season (less production in winter)
- Skin type (dark skin produces less vitamin D)
- Age (older skin is less efficient)
- Clothing and sunscreen
How do you get vitamin D through food?
Although sunlight is the most important source, you can also get vitamin D from food.
Foods rich in vitamin D:
- Fatty fish such as salmon, herring, mackerel and sardines
- Cod liver oil
- Egg yolks
- Enriched margarine and baking and frying products
- Fortified dairy products
It is more difficult for vegetarians and vegans to get enough vitamin D from food, which is why supplementation is often recommended.
How much vitamin D do you need per day?
The recommended daily amount (RDA) varies by age and situation:
| Age group / situation | Recommended amount |
| Babies and children up to 3 years old | 10 mcg (400 IU) |
| Adults up to 70 years old | 10 mcg (400 IU) |
| Elderly people aged 70 and over | 20 mcg (800 IU) |
| Pregnant women | 10 mcg (400 IU) |
| People with dark skin | 10-20 mcg (400-800 IU) |
| People who rarely go outside | 10-20 mcg (400-800 IU) |
In case of an established deficiency, higher doses may be prescribed, sometimes up to 50 mcg (2,000 IU) per day or a booster course of 25,000 to 50,000 IU per week.
Symptoms of a vitamin D deficiency
A vitamin D deficiency can cause various symptoms. Common symptoms include:
- Fatigue and listlessness
- Muscle weakness and muscle pain
- Bone pain, especially in the back and hips
- Slow wound healing
- Increased susceptibility to infections
- Hair loss
- Mood swings or depressive symptoms
- Increased risk of bone fractures
- Intestinal complaints
In children, a deficiency can lead to rickets, which manifests itself in crooked legs and retarded growth.
Who is at greater risk of a deficiency?
The following groups have a higher risk of vitamin D deficiency:
- People with dark skin (more melanin inhibits production)
- Elderly people over 70 years old
- People wearing fully covering clothing
- People who rarely go outside (e.g. elderly people in nursing homes)
- People with obesity
- People with certain intestinal disorders (such as celiac disease or Crohn’s disease)
- Vegans and strict vegetarians
Benefits of Vitamin D Supplementation
Stronger bones and teeth
Vitamin D prevents osteoporosis and helps form strong teeth, which is important to prevent osteoporosis and dental problems later in life.
More energy and better mood
Supplementation can help combat fatigue and make you feel more energetic, especially during the winter months when sunlight is limited.
Better resistance
Fewer infections and a faster recovery from colds or flu are often cited benefits of a healthy vitamin D status.
Improved muscle strength
In the elderly, vitamin D can contribute to increased muscle mass and strength, which significantly reduces the risk of falls.
Different forms of vitamin D supplements
Tablets and capsules
The most popular form, available in different dosages such as 800 IU, 5600 IU, and even 25,000 IU per capsule (e.g., colecalciferol capsules).
Drops
Convenient for babies and people who can’t swallow tablets. Often available in oil or water bases.
Chewable tablets
A tasty option for children and adults who have difficulty swallowing. Also available in combination with calcium.
Ampoules and injections
Prescribed for severe deficiencies or for people with absorption problems. For example, d-cura ampoules containing 25,000 IU or 100,000 IU.
When should you take vitamin D?
Although vitamin D can be taken at any time of the day, it is often recommended to do so with a meal as absorption is better then (fat promotes absorption).
For people who are sensitive to sleep problems, morning intake is recommended.
Side effects of vitamin D
With normal use, side effects are rare. However, excessive doses may cause symptoms such as:
- Nausea
- Decreased appetite
- Vomiting
- Constipation
- Thirst
- Lots of pee
- Kidney stones
- Cardiac arrhythmias
This is due to hypercalcemia (too much calcium in the blood). If in doubt, always consult a doctor.
Vitamin D during pregnancy and breastfeeding
Vitamin D is crucial for pregnant women. It supports the baby’s skeletal development and prevents pregnancy complications such as gestational diabetes and preeclampsia.
When breastfeeding, a daily intake of 10 mcg is recommended. Babies are often given extra vitamin D drops to prevent rickets.
Vitamin D and children
From birth to age 4, it is recommended to give 10 micrograms of vitamin D daily, regardless of whether the child is breastfed or bottle-fed. This is essential for healthy bone and tooth growth.
Vitamin D and the elderly
The risk of falls and fractures is high in older adults. Supplemental vitamin D improves muscle function and increases bone density. Therefore, a higher dose, usually 20 micrograms per day, is recommended for those over 70.
Vitamin D and people with dark skin
Due to the higher melanin content in the skin, less vitamin D is produced. Therefore, it’s important for this group to take extra supplements, especially during the fall and winter months.
Difference between vitamin D and vitamin D3
- Vitamin D3 (cholecalciferol) : The active form that the body produces itself under the influence of sunlight, and which is found in animal products.
- Vitamin D2 (ergocalciferol) : Plant source, less effective at increasing blood levels.
Supplements preferably contain D3 because of its better bioavailability.
What happens if you have too much vitamin D?
Vitamin D deficiency is rare, but can occur with prolonged high doses (>100 micrograms per day). Symptoms may include:
- Weakness
- Fatigue
- Nausea
- Cardiac arrhythmias
- Kidney failure
Stop taking supplements immediately and consult a doctor if you experience the above symptoms.
When is vitamin D reimbursed?
Since 2023, vitamin D is no longer covered by basic health insurance in the Netherlands. However, supplements are inexpensive and available without a prescription at pharmacies, drugstores, and supermarkets.
For people with medical indications, reimbursement through supplementary insurance may sometimes still be possible.
The relationship between vitamin D and magnesium
Vitamin D and magnesium work together. Magnesium helps activate vitamin D. A magnesium deficiency can make vitamin D less effective.
Combining vitamin D with magnesium supplements may therefore have benefits, especially for people with muscle cramps or fatigue.
Combination with calcium
Many calcium supplements also contain vitamin D. This combination is effective for osteoporosis because calcium strengthens bones and vitamin D optimizes their absorption. Examples include calcium/vitamin D chewable tablets (such as Costero or Calci Chew D3).
Vitamin D and nutrition: tips for daily use
- Eat oily fish 1-2 times a week
- Use margarine or half-fat margarine enriched with vitamin D
- Drink fortified milk or plant-based milk
- Choose eggs and meat in balance with vegetables
The role of vitamin D in skin problems
A vitamin D deficiency can contribute to skin problems like eczema and psoriasis. Although more research is needed, some people report improvement in their skin symptoms after optimizing their vitamin D status.
Frequently Asked Questions (FAQ)
How quickly does vitamin D work?
In case of a deficiency, it can take several weeks to months for the levels to recover. A booster treatment can accelerate this process.
What is the difference between vitamin D and D3?
Vitamin D3 is the most effective form and is recommended for supplementation. Vitamin D2 is less commonly used .
How do you know if you have a deficiency?
A blood test (25(OH)D) is the best way to measure your vitamin D status. Normal value: 50-100 nmol/L.
Can I take vitamin D with other vitamins?
Yes, vitamin D works well with vitamin K2, calcium and magnesium.
When should I take vitamin D: morning or evening?
Preferably in the morning with a meal for optimal absorption and to avoid possible sleep problems.
Conclusion: Vitamin D as the basis for your health
Vitamin D (cholecalciferol) is much more than a simple vitamin. It’s a powerful regulator of bone and muscle health, immune function, and energy levels. Especially in climates with limited sunlight, such as in the Netherlands and Belgium, supplementation isn’t a luxury for many people, but a necessity.
Sufficient sunlight, a vitamin D-rich diet and targeted supplementation can strengthen your health, resistance and vitality.