Where the worry comes from
The logic looks watertight at first glance. Vitamin D is made in the skin when UVB strikes a cholesterol derivative and converts it. Sunscreen blocks UVB. Therefore sunscreen must block vitamin D synthesis. It is a reasonable chain of reasoning and it appears in headlines every spring.
The reason it does not hold in practice is that each step is weaker than it looks. Sunscreen does not block all UVB, only a proportion. It is applied thinner than the laboratory dose, which lets more through than the label implies. It is applied unevenly, leaving gaps. It is rarely reapplied on schedule. And the amount of UVB required for vitamin D synthesis is small, well below the amount that produces visible reddening.
Put together, these mean that a person applying sunscreen in ordinary conditions is still receiving substantial UVB. Studies of typical sunscreen use, including in sunny climates and among people who use it consistently, have not demonstrated the deficiency that the theory predicts. Trials using laboratory conditions with full test dose application can show reduced synthesis, which is exactly what you would expect and is not how anyone applies sunscreen on a Tuesday.
The UK problem is latitude, not sunscreen
The far larger factor in Britain is where Britain is. The UK sits at a northern latitude where the sun's angle from roughly October to March is too low for sufficient UVB to reach ground level. During those months the skin cannot make vitamin D from sunlight regardless of exposure, clothing or sunscreen. Standing outside in a January field in a t shirt achieves nothing for vitamin D except discomfort.
This is why UK vitamin D deficiency is a winter problem rather than a sunscreen problem, and why NHS advice is framed around supplementation for the darker half of the year. Blaming sun protection for a phenomenon caused by the tilt of the earth misdirects attention from a straightforward and cheap intervention.
What UK guidance recommends
The official position is stable and easy to follow. Adults and children over one are advised to consider a daily supplement of ten micrograms of vitamin D during autumn and winter. Certain groups are advised to take it all year round: people who are rarely outdoors, those in care homes, people who usually cover most of their skin when outside, and people with deeper skin tones, who synthesise vitamin D more slowly from the same exposure.
Babies and young children have their own recommendations, which differ depending on whether they are breastfed or formula fed. The NHS vitamin D page sets out the current figures and the groups they apply to, and it is the reference to use rather than any supplement manufacturer's summary.
Dietary sources contribute but rarely suffice on their own. Oily fish, egg yolks, liver and fortified foods including many breakfast cereals and spreads all provide some. For most people in the UK, food alone does not cover winter requirements, which is why the supplement advice exists.
Deeper skin tones and the double bind
Melanin absorbs UVB, which reduces vitamin D synthesis from the same exposure. People with deeper skin tones living at northern latitudes are therefore at higher risk of low vitamin D status, and UK guidance recognises this by recommending year round supplementation for this group.
This can feel like a trap: protect from the sun and risk deficiency, or expose and risk pigmentation and damage. It is not really a trap, because supplementation resolves the vitamin D side cheaply and reliably, while there is no supplement for photoageing or hyperpigmentation. The rational approach is to supplement and protect, rather than trading one against the other. Our review of sunscreens for deep skin tones covers the protection side, including why visible light matters here.
Is deliberate sun exposure a sensible way to get vitamin D?
The case for short unprotected exposure has some support, and it is usually framed as a few minutes of midday sun on forearms and lower legs, several times a week, in the summer months only. That is a reasonable position for someone with fair skin who does not burn in that period.
Two cautions apply. The first is that the exposure needed for vitamin D is genuinely brief, and the risk arrives with duration. Deliberate exposure is not a licence for an afternoon in a deckchair. The second is that individual requirements vary with skin tone, age, body composition and latitude, so there is no single prescription that fits everyone. A supplement removes the guesswork.
Neither the British Association of Dermatologists nor Cancer Research UK recommends abandoning sun protection to raise vitamin D. Both recommend protection during strong sun alongside dietary and supplemental sources.
The summary worth remembering
Sunscreen used the way people actually use it has not been shown to cause vitamin D deficiency. UK winter latitude does prevent synthesis entirely for around half the year, and that is a real and well characterised problem with a simple and inexpensive answer. Supplement through the darker months, or year round if you have deeper skin or limited outdoor time, and keep using sun protection when the sun is strong.
If you are worried about your own levels, a blood test through a GP is the way to find out, rather than adjusting sun behaviour on the basis of a theory. For the other side of the equation, our guide to how much sunscreen to actually apply explains why most people are receiving considerably more UV through their sunscreen than they imagine.