vitamin
Vitamin D
The sunshine vitamin most UK residents are deficient in. Essential for bones, immunity and mood.
Overview
Vitamin D is a fat-soluble vitamin that functions more like a hormone in the body. It is produced in the skin when exposed to UVB sunlight. The UK's northerly latitude means that from October to April, sunlight intensity is insufficient to trigger meaningful skin production, making supplementation especially important during winter months. The NHS recommends all UK adults consider taking 10 micrograms (400 IU) daily during autumn and winter. Vitamin D receptors are found throughout the body, reflecting its broad physiological importance for bones, immune regulation, muscle function and mood.
Evidence rating
Vitamin D has exceptionally strong evidence for bone health and calcium metabolism. Evidence for immune function, respiratory infection reduction and mood is moderate to strong. Widespread deficiency in the UK population makes supplementation broadly beneficial for most people.
Common uses
- Strong EvidenceSupporting bone density and calcium absorption
- Moderate EvidenceImmune system support and reducing respiratory infections
- Moderate EvidenceMood support and seasonal affective disorder
- Strong EvidenceMuscle function and reducing fall risk in older adults
Safety & cautions
Worth checking with a pharmacist if you take medication.
Common forms
The preferred form. More effectively raises blood levels than D2.
K2 directs calcium to bones rather than arteries. Good for long-term use.
Plant-based. Less potent than D3. Suitable for vegans.
Food sources
- Salmon (fresh)Approx. 500-600 IU per 100g
- MackerelApprox. 360 IU per 100g
- Egg yolksApprox. 40 IU per yolk
- Fortified dairy and plant milksVaries by brand — check label