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UK/FLY/2023/2636 v3| November 2023


The ABC of Vitamin D

Now available on demand - This event outlines the role of vitamin D within the human body, along with the effects of vitamin D deficiency on health. It explores the evidence base for the pharmacological management of vitamin D deficiency and examines the clinical benefits of different treatment options for hypovitaminosis D.

Vitamin D Deficiency in the UK

Vitamin D is essential for calcium absorption and bone mineralisation which is positively associated with bone mineral density (BMD)1. Even though the human skin produces vitamin D following sun exposure, food and supplementation can also be a source of vitamin D.2,3 The biologically active form of vitamin D in the body is 1,25-dihydroxyvitamin D [1,25(OH)2D], however, assessing the vitamin D levels in the blood is done by testing for 25-hydroxyvitamin D [25(OH)D] levels in the blood serum. The criterion of Public Health England for vitamin D deficiency is 25(OH)D levels lower than 25nmol/L.2

According to the criteria of Public Health England and NICE for vitamin D, almost 55.4% of the population in the UK are either insufficient (serum 25(OH)D levels of 25-50 nmol/L) or deficient (serum 25(OH)D levels below 25nmol/L).

41.9% of the UK population suffers from vitamin D insufficiency and 13.5% of the UK population are vitamin D deficient.2

Some people are at greater risk of having a lack of vitamin D. Several studies in the past have shown that 40 - 100% of European elderly men and women living in the community (not in nursing homes) are deficient in vitamin D, and more than 50% of post-menopausal women have suboptimal levels of vitamin D.3 People with dark skin and Asian ethnic background also have a greater risk of vitamin D deficiency/insufficiency.2

Vitamin D deficiency is more common in the winter and spring compared to summer (4.5%) and autumn (7.6%). Not only elderly patients suffer from vitamin D deficiency. An additional British cohort study indicated that the average of vitamin D deficiency (in the winter and spring) is 15.5% among people who are 45 years old. When looking at demographic factors such as sex, the prevalence of vitamin D deficiency is approximately 24% in men and 21.7% in women aged 19-64 years. In spring, autumn and winter, the proportion of vitamin D deficiency in the northern part of the UK is higher than in the southern part of the country. Participants in Scotland have the highest proportion of vitamin D deficiency (23.5%) compared with other UK centres.2

Vitamin D deficiency is more prevalent among current smokers and people that spend less time outdoors in winter.

The proportion with vitamin D deficiency is lower among people with healthy weight and normal BMI. Deprivation increases the odds of vitamin D deficiency or insufficiency, while taking vitamin D is associated with a lower risk of vitamin D deficiency or insufficiency in the participants.2

This article draws on information from the UK Biobank which was compiled from 2006-2010 by recruiting participants aged 40-69 years throughout the UK.


1. Eamon Larid, et al. Vitamin D and Bone health: Potential Mechanisms. Nutrients 2010, 2, 693-724.

2. Lin L-Y et al. Distribution of vitamin D status in the UK: a cross-sectional analysis of UK Biobank. BMJ Open 2021.

3. Michael F. Holick. Vitamin D Deficiency. N Engl J Med 2007 357:266-81