What is vitamin D?
Vitamin D is a fat-soluble hormone that the body needs to absorb calcium and phosphorus from food. Its best-known role is keeping bones and teeth strong, but receptors for vitamin D have been found in nearly every tissue. It also supports muscle function, immune regulation, and mood.
Most of our vitamin D comes from sunlight: ultraviolet B (UVB) rays trigger its production in the skin. Only a small share comes from food — fatty fish, egg yolks, fortified dairy.
The Cypriot paradox
You might expect vitamin D deficiency to be a problem of the cold north. In fact, studies in Cyprus repeatedly find deficiency in 30–50% of adults and an even higher share among older people, women who veil for cultural reasons, and patients with darker skin or chronic illness.
The reasons are intuitive once stated:
- Modern lives are spent mostly indoors, even in sunny countries
- Clothing, sunscreen, and the avoidance of midday sun (sensible against skin cancer) all reduce UVB exposure
- After about age 50, the skin's capacity to produce vitamin D drops by half
- Obesity sequesters vitamin D in fat tissue, reducing what is available
Symptoms
Mild deficiency is often silent. As levels fall further, symptoms include:
- Persistent fatigue and low mood
- Muscle weakness and aches
- Bone pain, especially in the lower back, hips and ribs
- More frequent infections
- In children: delayed growth and rickets (bone deformities)
- In adults: osteomalacia (soft, painful bones) and accelerated osteoporosis
Diagnosis
A simple blood test for 25-hydroxyvitamin D [25(OH)D] is the standard. Common thresholds:
- Below 20 ng/mL (50 nmol/L): deficiency
- 20–30 ng/mL (50–75 nmol/L): insufficiency
- 30–50 ng/mL (75–125 nmol/L): adequate
- Above 100 ng/mL: potentially toxic
What helps
A pragmatic approach combines safe sun, food, and supplements:
- 10–20 minutes of midday sun on bare arms and legs, several times a week, outside peak summer hours
- Oily fish twice a week (sardines, salmon, mackerel — all readily available in Cyprus)
- Eggs and fortified dairy
- For confirmed deficiency, oral vitamin D3 (cholecalciferol) supplementation, dosed by a clinician based on your blood level
Self-prescribing very high doses is unwise: vitamin D toxicity is rare but real, causing dangerous calcium build-up.
Who should be tested
Ask your doctor about a vitamin D test if you:
- Are over 65
- Are pregnant or breastfeeding
- Have darker skin
- Spend most of your day indoors
- Have osteoporosis, fractures, or chronic kidney or liver disease
- Take medications that affect vitamin D metabolism (e.g. certain anticonvulsants)
A general practitioner is the right first stop. Endocrinologists, rheumatologists, and orthopaedic specialists may be involved when bone disease is established.