The Netherlands sits at 52 degrees north latitude. Between October and March, the sun is too low to provide sufficient UVB radiation for vitamin D production in your skin. This makes vitamin D deficiency one of the most common nutritional deficiencies in the country, affecting an estimated 40-60% of the population.
How vitamin D works
Vitamin D is technically a hormone. Your body produces it when UVB rays reach your skin. It is then converted in the liver and kidneys to its active form. Key functions: calcium absorption for bone health, immune system modulation, muscle function and mood regulation.
Why the Netherlands is at extra risk
Geographic latitude (insufficient UVB October-March), indoor lifestyles (90% of time spent indoors), sunscreen use (blocks 95-99% of UVB), limited dietary sources, and declining skin production with age all contribute. These factors stack, making deficiency almost inevitable without conscious supplementation.
Risk groups
- People with darker skin - melanin blocks UVB, requiring longer sun exposure
- Older adults (70+) - reduced skin production, less outdoor time
- People wearing covering clothing - insufficient UV exposure
- Indoor workers - glass blocks UVB completely
- Pregnant women - increased requirements
- People with obesity - vitamin D is sequestered in fat tissue
Symptoms of deficiency
Mild deficiency often produces no clear symptoms. More significant deficiency can cause fatigue, bone and muscle pain (especially lower back and hips), muscle weakness, low mood, increased susceptibility to infections and slow wound healing.
Supplementation
The Dutch Health Council recommends: 10 ug (400 IU) daily for most adults, 20 ug (800 IU) for those over 70, and 10-25 ug for people with dark skin or covering clothing. Vitamin D3 is preferred over D2. Take it with a meal containing fat for better absorption.
When to test
Testing is worthwhile if you have symptoms consistent with deficiency, belong to a risk group, have osteoporosis, or want to verify your supplementation is adequate. The test measures 25-hydroxyvitamin D. Above 50 nmol/L is sufficient, 30-50 is insufficient, below 30 is deficient.
Vitamin D and calcium work closely together. Without adequate vitamin D, calcium absorption drops, so it is worth checking both when deficiency is suspected.
Frequently asked questions
How much vitamin D per day?
10 ug (400 IU) for most adults, 20 ug (800 IU) for over-70s. Your doctor may prescribe higher doses temporarily for confirmed deficiency. Do not self-medicate above 100 ug/day.
Can you take too much?
Yes, though rare at normal doses. Vitamin D is fat-soluble and stored in the body. Chronic excessive intake (above 100 ug/day for months) can cause hypercalcaemia. Stick to recommended doses.
Can I get enough from food?
Difficult in the Netherlands. Oily fish is the richest source but provides only 5-10 ug per portion. Eggs and fortified products contribute small amounts. For most Dutch residents, supplementation is necessary, especially in winter.
Do sunbeds help?
Sunbeds primarily emit UVA, not the UVB needed for vitamin D production. The skin cancer risk is significant. Supplementation is safer and more effective.
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