Vitamin D Deficiency - Why Almost Every African in the UK Is Deficient and What to Do

If I had to name one blood test result I wish I had ordered sooner for every African patient I have seen in the UK, it would be vitamin D.

Not because it is dramatic. Not because it causes rare, exotic disease. But because of how consistently - almost universally - it is severely deficient in patients who have been tired for two years, achey for three, struggling with their mood for longer than they can pinpoint. Patients who have had thyroid function tests, full blood counts, inflammatory markers - all returned normal - and who have been told there is nothing to explain how they feel.

Then I check vitamin D. And there it is: 14 nmol/L. 19 nmol/L. Once, memorably, 8 nmol/L in a 34-year-old who had been seen by three different doctors over two years and been told repeatedly that her fatigue was stress-related.

It is not complicated biology. Dark skin evolved in equatorial regions where UV radiation is intense year-round. Melanin evolved as natural sunscreen. In Nigeria, in Zimbabwe, in Ghana, that melanin is an advantage - protecting against UV damage in intense sunlight. In Birmingham, in Edinburgh, in Manchester, at latitudes where UVB radiation is weak for most of the year and absent between October and March, that same melanin efficiently blocks the limited UV that reaches you. The result is biologically predictable: African adults living in the UK cannot synthesise adequate vitamin D from sunlight for approximately 6-8 months of the year. Supplementation is not optional. It is physiologically necessary.

What vitamin D actually does

The classical role of vitamin D is calcium and phosphate regulation - it increases calcium absorption from the gut and is essential for bone mineralisation. Severe deficiency causes rickets in children (soft, deformed bones) and osteomalacia in adults (bone pain, weakness, and increased fracture risk).

But these classical manifestations are seen at very severe deficiency. The effects of moderate deficiency - the level that most African adults in the UK are at - are more subtle and more diffuse:

Musculoskeletal: Diffuse bone aching and muscle weakness. Often described as aching all over, particularly in the back, hips, and legs. Frequently attributed to ageing, stress, or fibromyalgia before vitamin D is checked.

Fatigue: Often profound, disproportionate to activity levels or sleep. One of the most commonly reported improvements after vitamin D repletion.

Immune function: Vitamin D is essential for the normal function of both innate and adaptive immunity. Deficiency is associated with increased susceptibility to respiratory infections and has been linked in multiple studies to higher risk of autoimmune conditions.

Mood: Vitamin D receptors are present throughout the brain. Deficiency is associated with higher rates of depression and seasonal affective disorder. Whether repletion improves mood in deficient individuals remains an active research area, but the association is consistent.

Cardiovascular: Multiple studies show associations between vitamin D deficiency and higher blood pressure, insulin resistance, and cardiovascular risk.

Fertility and pregnancy: Vitamin D plays roles in reproductive health and pregnancy. Deficiency during pregnancy is associated with higher rates of pre-eclampsia, gestational diabetes, and low birth weight.

Fibroid growth: Emerging evidence suggests vitamin D may inhibit fibroid development. Given the near-universal deficiency in Black women in the UK and the dramatically higher fibroid rates, this is an area of active investigation.

Understanding your result

The 25-hydroxyvitamin D (25-OHD) blood test measures your vitamin D status. Interpretation:

Note that many NHS laboratories report the reference range as above 50 nmol/L as adequate. Many vitamin D specialists and the evidence base suggest that for symptomatic benefit, levels above 75 nmol/L are the target.

Case study: Grace's mystery fatigue resolved

Grace, 38, a secondary school teacher from Ghana based in Leeds, came to me with eight months of persistent fatigue. She was sleeping 8-9 hours per night and waking unrefreshed. She was experiencing significant hair shedding. She felt cold much of the time.

Previous investigations: thyroid function normal, full blood count showed mild anaemia from low ferritin (iron was supplemented - with partial improvement), inflammatory markers normal. Vitamin D had not been checked at any point.

I added it. Her 25-hydroxyvitamin D: 18 nmol/L. Severely deficient.

I prescribed a loading dose regime: 40,000 IU vitamin D3 weekly for 7 weeks (a standard loading regimen for severe deficiency), followed by 2,000 IU daily maintenance.

At her six-week review, before we had even recharged her stores to the optimal range, she described significant improvement in energy, mood, and the bone aching she had not mentioned but had been living with. At her 12-week review, with a level now at 82 nmol/L: "I feel like myself again. The fatigue I thought was just part of my life is almost gone."

"I am slightly annoyed it took this long for someone to check," she said.

I understood her frustration entirely. A test costing a few pounds had, within weeks, substantially resolved symptoms that had been investigated unsuccessfully for eight months.

What to take and how

Vitamin D3 (cholecalciferol): Always take D3, not D2. D3 is significantly more effective at raising and maintaining 25-OHD blood levels - approximately 2-3 times more effective than D2 at equivalent doses.

For deficiency correction (under GP supervision): Loading doses of 40,000-60,000 IU per week for 6-8 weeks, followed by maintenance dosing.

For ongoing maintenance (all Black adults in UK): 1,000-2,000 IU daily. The NHS recommendation of 400 IU is the minimum to prevent deficiency in the general population - for dark-skinned adults it is inadequate to maintain optimal levels. 1,000-2,000 IU is safe and appropriate.

Vitamin K2: Some evidence suggests taking vitamin K2 alongside vitamin D3 may improve calcium deposition in bone and reduce arterial calcification. While not essential, combined D3/K2 preparations are available and reasonable.

With food: Vitamin D is fat-soluble. Take with your largest meal of the day to maximise absorption.

Ask your GP to check your level. If they are reluctant (some GPs test only when symptoms are clearly present), private testing via a home blood spot kit is available for approximately 30-40 pounds. Given the near-universal deficiency in dark-skinned UK adults, testing is almost always worthwhile.

Sources: Darling AL et al, American Journal of Clinical Nutrition 2021 (vitamin D deficiency in UK Black adults); Webb AR et al, Nutrients 2018 (UVB and vitamin D synthesis at UK latitudes); Holick MF, NEJM 2007 (landmark vitamin D review); Scientific Advisory Committee on Nutrition - Vitamin D and Health Report 2016; NHS - Vitamin D; Heaney RP et al, American Journal of Clinical Nutrition 2011 (vitamin D supplementation recommendations).