Vitamin D and the immune system is one of the most talked-about topics in nutrition. Let's separate the science from the hype.
The authorised claim
The UK (via the EFSA register) authorises the claim: 'Vitamin D contributes to the normal function of the immune system.' This is a general health claim, meaning that vitamin D is needed for the immune system to work normally. It does not mean vitamin D prevents illness.
What the research shows
Vitamin D receptors are found on many immune cells, and vitamin D plays a role in both the innate and adaptive immune responses. Some studies have suggested that vitamin D supplementation may reduce the risk of respiratory infections, particularly in people who are deficient.
What vitamin D does NOT do
Vitamin D does not prevent colds, flu or COVID-19. No supplement can claim to prevent or treat any disease. If you see a product making such claims, it is not compliant with UK regulations.
The practical takeaway
If you're low on vitamin D — and many UK adults are in winter — supplementing to reach adequate levels supports normal immune function. But taking extra vitamin D beyond what you need won't supercharge your immune system. It's about meeting your baseline, not exceeding it.
How much to take
The NHS recommends 10µg (400 IU) per day in autumn and winter. Our D3 + K2 provides 100µg (4,000 IU). Don't take both without checking with your GP.
Food supplements should not replace a varied, balanced diet and a healthy lifestyle. This guide is general information, not medical advice. If you are pregnant, breastfeeding, take medicine or have a health condition, speak to your GP or pharmacist before taking a supplement.
Sources
- 1.NHS. Vitamin D. nhs.uk.
- 2.EFSA Register of Nutrition and Health Claims. efsa.europa.eu.
- 3.SACN. Vitamin D and Health Report. GOV.UK, 2016.
