Vitamin D in the UAE: why sunshine is not the whole story

A sunny country with low vitamin D

Skin makes vitamin D from sunlight¹. The UAE has abundant sunlight², so it might seem an easy place to get enough. Research from the UAE shows otherwise.

A 2025 systematic review pooled 35 studies with 28,260 participants in the UAE². For adults, the pooled average blood level was 17.63 ng/mL. That is below 20 ng/mL, the cut-off the review used for deficiency².

A large Abu Dhabi study looked at 12,346 Emirati participants in the Weqaya screening programme between 2011 and 2012³. Using a cut-off of 50 nmol/L, 72% were deficient and a further 10% insufficient³.

The picture is similar across the Gulf. A 2019 review reported that close to 86% of the Qatar Biobank population had vitamin D inadequacy. It cited UAE figures of up to 82.5% with deficiency or insufficiency⁴.

A note on the numbers: studies use different cut-offs. The US Office of Dietary Supplements (ODS), part of the National Institutes of Health, links levels below 30 nmol/L (12 ng/mL) with deficiency. It describes 50 nmol/L (20 ng/mL) or more as adequate for most people¹. The Abu Dhabi study counted anything below 50 nmol/L as deficient³. So percentages depend on the definition used.

Why sunshine is not enough

The authors of the 2025 UAE review point to four likely reasons²:

• clothing practices that leave less skin exposed to the sun
• very hot weather that discourages outdoor activity
• darker skin tones, which reduce vitamin D production
• low intake of foods rich in vitamin D

Individual studies in the review show how these play out. In one, Emirati women of childbearing age had a mean level of 8.6 ng/mL, against 64.3 ng/mL in Europeans living in the UAE. The difference was linked to clothing that covered most of the body². In another, people who spent most of their working day sitting had the lowest average levels².

The seasonal pattern is the reverse of what many people expect. In the Abu Dhabi study, average levels were highest in January, February and April, the short winter season. They were lowest in July and August, the hottest months³.

ODS explains the skin effect: more of the pigment melanin reduces the skin's ability to produce vitamin D from sunlight¹. It also lists season, time of day, cloud cover, smog and sunscreen as factors¹. It names people who wear long robes, dresses or head coverings, and people who are homebound, as having limited sun exposure¹.

The 2019 Gulf review adds two more factors. One is the link between higher body weight and lower vitamin D levels. The other is gene variants associated with vitamin D levels⁴.

Food sources

The best natural sources are fatty fish, such as trout, salmon, tuna and mackerel, and fish liver oils¹. Beef liver, egg yolks and cheese also contain some¹.

Amounts vary widely. Examples from the ODS food table¹:

• farmed rainbow trout, cooked, 3 ounces (about 85 g): 16.2 µg
• sockeye salmon, cooked, 3 ounces: 14.2 µg
• white mushrooms exposed to UV light, half a cup: 9.2 µg
• one large egg, scrambled: 1.1 µg
• canned light tuna in water, 3 ounces: 1.0 µg

The Gulf review notes that diet usually supplies less than 10% of the body's vitamin D⁴.

Test first, then talk to your doctor

The main way to check vitamin D status is a blood test for 25-hydroxyvitamin D, or 25(OH)D¹. It has a fairly long half-life of about 15 days in the blood¹.

Abu Dhabi's Department of Health uses the same bands as ODS in its vitamin D coverage policy for Thiqa members. Below 30 nmol/L is associated with deficiency, which can lead to rickets in children and osteomalacia in adults. Above 125 nmol/L is linked to potential adverse effects⁵.

The same policy sets out when testing is covered⁵. Examples include:

• bone conditions such as osteoporosis
• chronic kidney disease, liver failure or malabsorption
• some medicines, such as glucocorticoids and anti-seizure drugs
• a yearly test for people over 65

In other words, testing is tied to medical need.

More is not always better. Too much vitamin D can raise blood calcium, which can cause nausea, vomiting, muscle weakness and kidney stones¹. ODS lists the adult upper limit as 100 µg (4,000 IU) a day¹. The European Food Safety Authority also set 100 µg a day for adults, including during pregnancy and breastfeeding⁶.

Medicines matter too. ODS notes that orlistat, together with a reduced-fat diet, can reduce vitamin D absorption. It adds that statins may reduce the body's own vitamin D production¹.

A doctor can tell you whether you need a test, explain the result, and advise whether a supplement makes sense for you.

This article is general information, not medical advice. Talk to your doctor or pharmacist before starting a supplement, especially if you are pregnant, breastfeeding, taking medicines or managing a health condition.