Vitamin D Deficiency in the UAE: Why It Is So Common Here

The paradox: sunshine everywhere, deficiency everywhere

It is one of the more counter-intuitive findings in regional medicine. In a country with sunshine almost every day of the year, published studies across the UAE and the wider Gulf have consistently reported high rates of vitamin D deficiency.

The explanation is not mysterious once you look at how people actually live here.

• The heat drives people indoors. For a large part of the year, the outdoors is genuinely uncomfortable in the middle of the day — which is precisely when the sun produces vitamin D most efficiently.
• Air-conditioned life is indoor life. Home to car to office to mall, often without meaningful sun exposure at any point.
• Clothing covers the skin, for cultural, professional or practical reasons. Vitamin D synthesis requires skin actually exposed to UVB.
• Sunscreen, correctly used, reduces synthesis — which is not an argument against sunscreen, but it is part of the picture.
• Darker skin needs longer exposure to produce the same amount, because melanin reduces UVB penetration.
• Glass blocks UVB. Sitting by a sunny window produces essentially none.

None of these are failings. They are a reasonable response to the climate. But together they explain why "we live somewhere sunny" does not translate into adequate vitamin D.

What vitamin D actually does

Its best-established role is in calcium and phosphate handling, and therefore in bone. Vitamin D allows the gut to absorb calcium properly. Without enough, bone mineralisation suffers — severely in children, and in adults contributing to bone softening, bone pain and increased fracture risk over time.

It also has a role in muscle function, and deficiency is associated with muscle weakness, particularly in the large muscles around the hips and shoulders.

Beyond bone and muscle, vitamin D receptors are found throughout the body, and this has generated an enormous amount of research and an even larger amount of claim. The distinction between "is associated with" and "supplementing improves" is where most of the confusion lives, and it is worth being careful about.

The symptoms, and an honest caveat

Deficiency can cause:

• Fatigue and low energy
• Muscle aches and weakness, particularly around the hips and thighs
• Bone pain or tenderness, often in the lower back, pelvis or legs
• Low mood
• Frequent or slow-healing problems in some cases

Here is the caveat that matters. Every one of those symptoms has many possible causes, and vitamin D has become a popular explanation for feeling generally unwell.

Sometimes it is genuinely the answer. Often it is not, and treating a borderline vitamin D level while an anaemia, a thyroid problem, sleep deprivation, or something else goes unexamined is a real risk of the current enthusiasm for it. Persistent fatigue deserves a proper assessment, not just a single number.

Who should actually be tested

This is where we differ from the "test everything annually" approach, and it is consistent with what we say elsewhere on this site about over-testing.

Testing is reasonable when there is a reason to expect a problem or when the result will change what you do:

• Symptoms consistent with deficiency, particularly bone pain or proximal muscle weakness
• Very limited sun exposure, or skin routinely covered
• Osteoporosis, a fragility fracture, or a bone health assessment
• Malabsorption conditions — coeliac disease, inflammatory bowel disease, after bariatric surgery
• Chronic kidney or liver disease
• Certain medications that affect vitamin D metabolism
• Pregnancy and breastfeeding, and in infants and young children
• Confirming a response after treating a known deficiency

Testing is usually not necessary for a healthy adult with no symptoms and no risk factors who is simply having an annual check. If the intention is to take a modest maintenance dose anyway, the test frequently does not change the decision — and a test that cannot change the decision is not earning its place.

What the numbers mean

Vitamin D status is measured as serum 25-hydroxyvitamin D.

Laboratories and guidelines differ on exact thresholds, which is a common source of confusion — the same result can be reported as "deficient" by one lab and "insufficient" by another. Broadly, there is a level below which deficiency is clear and treatment is warranted, a middle band described as insufficiency where the picture is less certain, and a sufficient range.

Two practical points. First, treat the person and the symptoms, not the number in isolation. Second, being marginally below a threshold in a well person with no risk factors is not the same clinical situation as a clearly low level in someone with bone pain.

How it is corrected

Sunlight is the natural source, and in this climate it is best sought outside the middle of the day — early morning or later afternoon, for short periods, with skin actually exposed. This is more realistic in the cooler months, which is one reason status here often varies with the season in the opposite direction to Europe.

Diet contributes modestly. Oily fish is the best natural source; egg yolk and fortified products contribute smaller amounts. It is difficult to correct a genuine deficiency by diet alone.

Oral supplementation is the reliable way to correct a confirmed deficiency. Dosing regimens vary — daily, weekly, or a loading course followed by maintenance — and the right one depends on how low the level is and on any underlying cause. This is worth getting from a clinician rather than from a shelf, because the correct dose for treating deficiency and the correct dose for ongoing maintenance are not the same.

What supplementation will, and will not, do

This is the section most likely to differ from what you have read elsewhere.

It will correct a deficiency, support bone health, and — where deficiency was genuinely causing them — improve bone pain and proximal muscle weakness. In people at risk of fragility fractures, adequate vitamin D and calcium are part of established bone health management.

What has not been demonstrated is that giving supplements to people who are not deficient produces the broad benefits often claimed for it. Several large randomised trials have tested vitamin D supplementation in general populations for outcomes including cardiovascular disease and cancer, and did not find the benefits that observational associations had suggested.

That gap between association and causation is the honest heart of the vitamin D story. Low vitamin D is associated with poor health outcomes — but people who are unwell, indoors, inactive and eating poorly also tend to have low vitamin D. Correcting the number does not necessarily correct the situation that produced it.

So: correct a real deficiency. Do not expect a supplement to substitute for sleep, movement, or a proper assessment of why you feel tired.

Can you take too much?

Yes, and this is worth stating because vitamin D is widely available in very high-dose forms.

It is fat-soluble and accumulates. Excessive intake over time can raise blood calcium, producing nausea, excessive thirst and urination, constipation, confusion, and — if prolonged — kidney damage and kidney stones.

This is not a reason for fear at sensible doses. It is a reason not to self-prescribe very high doses indefinitely, and not to assume that if some is good, more is better. High-dose regimens should be prescribed and, where relevant, monitored.

How often to retest

Once a deficiency has been treated, rechecking to confirm the response is reasonable.

After that, repeating the test annually out of habit in a person who is stable, supplemented and symptom-free rarely changes anything. Retest when something changes — new symptoms, a new condition, a change in medication, or a change in how you live.

What we would do at IDUNN

We would ask why the question has come up before ordering the test. If there are symptoms, risk factors, or a bone health reason, testing is appropriate and we would do it.

If the answer is that you feel persistently tired, we would want to look wider than one vitamin. Fatigue has many causes, and finding a borderline vitamin D level is an easy way to stop looking too early.

Where a deficiency is confirmed, we would correct it properly with an appropriate regimen and confirm the response, then move to sensible maintenance rather than indefinite high-dose treatment.

And we would be straightforward about what it will do. Correcting a real deficiency is worth doing. It is not a general-purpose remedy, and we would rather say that than sell it as one.