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Do you really need a vitamin D supplement? (Spoiler: probably yes!)


Most of us, including me, like to believe a healthy diet is enough to meet our nutrient needs – and for the most part, it is.

But vitamin D is different.


The latest UK data show that deficiency is common and seasonal, making supplementation a smart move for almost everyone.


If you’re responsible for workplace wellbeing, this is one of the simplest, highest-impact steps you can champion. A small, inexpensive supplement can protect employees’ immunity, energy and musculoskeletal health – helping people feel and perform at their best all winter.  (check complete checklist at the end)


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'Food first' except... when it comes to vitamin D


Vitamin D is the odd one out because food can only give us a little. Our main source is sunshine. And no matter how perfect your diet is, the British winter sun just isn’t strong enough for your skin to make enough vitamin D.


The latest UK National Diet and Nutrition Survey (NDNS, 2019–2023)[1][2] shows that:


  • Around 18% of adults aged 19–64 have vitamin D deficiency (blood level below 25 nmol/L) in the non-winter months, rising to 31% in winter.

  • Teenagers (11–18 yrs) are even more at risk: up to 36% are deficient in winter.

  • Younger children (4–10 yrs) and older adults (65+ yrs) also show deficiency rates of around 10–12% depending on the season.

  • Across all age groups, average intakes are well below the UK recommended 10 µg/day (400 IU).


That’s why UK guidance (SACN)[3][4] recommends that everyone aged 4 years and over takes a daily 10 µg (400 IU) supplement from October to April.


People with darker skin, those who cover their skin, or anyone who rarely gets outdoors are advised to supplement all year round.



What does vitamin D actually do?

Vitamin D has wide-ranging effects on bone, immune, and metabolic health, with ongoing research into many other outcomes[5]


  • Bone & muscle health – Helps absorb calcium and phosphorus, keeping bones, muscles and teeth strong. Deficiency can lead to bone pain, muscle weakness, osteoporosis and higher fracture risk.

  • Immune function – Supports the immune system. Supplementation may reduce the risk of respiratory infections; evidence for COVID-19 benefit is still mixed.

  • Mood & mental health – Low blood levels are common in people with depression. Some studies show benefits from supplementation, though more high-quality trials are needed.

  • Other areas under research – Diabetes, cancer, iron metabolism, metabolic health, cognitive function… there’s potential, but no firm conclusions yet.


Bottom line: keeping vitamin D in a good range is important, even if many of the “bonus” effects are still being investigated.


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Checklist: how to pick a vitamin D supplement


Not all supplements are equal. Here’s what to look for:

  • Type – Vitamin D3 (cholecalciferol) is more effective than D2.

  • Dose – Aim for about 10 µg (400 IU) daily. Slightly higher doses (25 µg / 1,000 IU) are generally safe for most adults but depend on your starting level.

  • Quality – Choose an established brand (ideally with third-party testing or UK/EU pharmacy certification) to ensure dose accuracy and purity. Vitamin D doesn’t need to be expensive though.

  • Format – capsules, pills or spray all work – pick the one you’ll reliably take.

  • Timing – Take with a meal containing some fat to improve absorption.

  • Safety limits – Stay below 100 µg (4,000 IU) per day[6]. If taking several supplements watch for compounding; You can overdo it. Avoid mega-doses unless prescribed.



Take-home message


Good vitamin D levels matter for bones, muscles, immunity and more. Because the UK winter sun can’t provide enough, a daily 10 µg supplement from October to April is a simple, safe way to protect your health.If you’re at higher risk (e.g. darker skin, low sun exposure), you might need one all year round.

 

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References


[2] MRC Epidemiology Unit, Cambridge. NDNS 2019–2023: Dietary Deficiencies Highlight. 2025. https://www.mrc-epid.cam.ac.uk/blog/2025/06/12/ndns-2019-2023-dietary-deficiencies/


[3] Scientific Advisory Committee on Nutrition (SACN). Vitamin D and Health Report  (2016) https://assets.publishing.service.gov.uk/media/5a804e36ed915d74e622dafa/SACN_Vitamin_D_and_Health_report.pdf


[4] Scientific Advisory Committee on Nutrition (SACN). Fortifying Foods and Drinks with Vitamin D: Main Report (Rapid Review). 2024. https://www.gov.uk/government/publications/fortifying-food-and-drink-with-vitamin-d-a-sacn-rapid-review/fortifying-foods-and-drinks-with-vitamin-d-main-report


[5] Lanham-New SA, et al. (2022). Vitamin D – A multi-disciplinary approach to (1) elucidate its role in human health and (2) develop strategies to improve vitamin D status in the UK population. Nutrition Bulletin, 47(4), 515–541. https://onlinelibrary.wiley.com/doi/10.1111/nbu.12547


[6] European Food Safety Authority (EFSA). Vitamin D: scientific opinion on dietary reference values. EFSA Journal2023;21(7):8145. https://www.efsa.europa.eu/en/efsajournal/pub/8145

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