Vitamin D deficiency

Vitamin D and its active metabolite 1,25-dihydroxyvitamin D (1,25(OH)2D) have classical actions on calcium balance and bone metabolism (1).

• Insufficient 1,25(OH)2D leads to inadequate absorption of calcium and phosphate which results in secondary hyperparathyroidism and lack of new bone mineralisation - rickets in children and osteomalacia in adults.
• A consensus statement representing the unified views of a number of organisations (the British Association of Dermatologists, Cancer Research UK, Diabetes UK, the Multiple Sclerosis Society, the National Heart Forum, the National Osteoporosis Society and the Primary Care Dermatology Society), states that the evidence suggesting that vitamin D might protect against cancer, heart disease, diabetes, multiple sclerosis and other chronic diseases is still inconclusive. Furthermore, there is no standard definition of what constitutes an optimal level of vitamin D (2).

Vitamin D deficiency is common in northern UK.

• In a recent cross-sectional study (3), results showed that vitamin D status varied among different ethnic groups and by season and geographical area within the UK:
  • vitamin D deficiency was more common in winter and spring, and its prevalence was higher in the northern UK than the southern UK
  • male sex, abnormal BMI, Asian and black ethnic backgrounds, and tobacco smoking were associated with higher odds of vitamin D deficiency
  • taking vitamin D supplements and drinking alcohol were associated with lower odds of vitamin D deficiency
  • these results provide some evidence supporting the Public Health England recommendation for taking vitamin D supplementation in winter and for people with black or Asian ethnic background
• Prevalence of vitamin D deficiency in commonly encountered clinical patient populations is as follows (4):
  • nursing home or house bound residents (mean age 81 years): 25-50%
  • elderly ambulatory women aged >80 years: 44%
  • women with osteoporosis aged 70-79 years: 30%
  • patients with hip fractures (mean age 77 years): 23%
  • African American women aged 15-49 years: 42%
  • adult hospitalised patients (mean age 62 years): 57%

Vitamin D deficiency and chronic obstructive pulmonary disease (COPD).

• Men with COPD were more likely to be vitamin D deficient than those with normal lung function (5).
  • Vitamin D deficiency is associated with increased all-cause mortality in older men with no lung impairment as well as in those with restrictive or obstructive lung impairment.

Opinions on optimal vitamin D serum concentrations in adults vary (1).

• According to the Endocrine Society Task Force guidelines vitamin D deficiency is defined as a serum 25-hydroxycholecalciferol (25OHD) <50 nmol/L but advocated that 25OHD concentration should exceed 75 nmol/L, to maximise the effect of vitamin D on calcium, bone and muscle metabolism.
• The UK Royal Osteoporosis Society recommends the following vitamin D thresholds for UK practitioners in respect to bone health:
  • serum 25OHD < 25 nmol/L is deficient
  • serum 25OHD of 25–50 nmol/L may be inadequate in some people
  • serum 25OHD > 50 nmol/L is sufficient for almost the whole population (1)

References

• (1) Royal Osteoporosis Society (2020). Vitamin D and Bone Health: A Practical Clinical Guideline for Patient Management.
• (2) NHS (2010). Vitamin D position statement. Accessible at https://www.nhs.uk/livewell/summerhealth/documents/concensus_statement%20_vitd_dec_2010.pdf (accessed 15 May 2022).
• (3) Lin L, Smeeth L, Langan S, et al. Distribution of vitamin D status in the UK: a cross-sectional analysis of UK BiobankBMJ Open 2021;11:e038503. doi: 10.1136/bmjopen-2020-038503.
• (4) Kennel KA, Drake MT, Hurley DL. Vitamin D Deficiency in Adults: When to Test and How to Treat. Mayo Clinic Proceedings. 2010;85(8):752-758.
• (5) Wannamethee SG, Welsh P, Papacosta O, et al. Vitamin D deficiency, impaired lung function and total and respiratory mortality in a cohort of older men: cross-sectional and prospective findings from The British Regional Heart Study. BMJ Open 2021;11:e051560. doi: 10.1136/bmjopen-2021-051560.