Vitamin D is important for lots of things including bone health and for keeping your immune system in shape. It’s produced when your skin is exposed to the sun, which can be a serious problem in the winter months. Yes but now it’s sunny I hear you cry, which leads to a common question: “Does using sunscreen block vitamin D absorption?” Time to debunk some myths.
When the sun is shining (every now and then in the UK) and your skin is exposed, it will create vitamin D. How? Science. The ultraviolet B (UVB) rays from the sun interact with a protein called 7-DHC in the skin and through a series of chemical reactions, it’s converted into the active form of vitamin D.
“Thanks for the lesson doc but it’s summer now so…. Does caking myself in sunscreen stop me from producing Vitamin D?”
Well, not really. Here are the facts.
- Ultraviolet radiation is a form of electromagnetic radiation that comes from the sun as well as man-made sources such as tanning beds, and can damage skin. People use sunscreen to protect against skin cancer, specifically as a result of UVB rays (think B for burn).
- Most sunscreens contain chemicals that either block UV rays or absorb them.
- There is little or no clinical evidence to suggest that using sunscreen impacts vitamin D levels or increases the risk of vitamin D deficiency.
- A study from my alma mater, King’s College London, determined that even when used optimally to prevent sunburn, sunscreen allowed excellent vitamin D synthesis.
“Alright fine, I’ll wear my sunscreen then. But do I need to be exposed in the sun every day to produce enough vitamin D to be healthy?”
No. If you’re eating a varied, healthy and balanced diet, chances are you’re getting enough vitamin D. The recommended daily dose is 10 micrograms or 400 IU (International Units) Good sources include red meat, liver, oily fish, eggs and of course, vitamin D-fortified foods. If you’re struggling to eat these every day or you’re plant-based, these might help.
Let’s go a bit deeper, just for the nerds. Vitamin D is fat soluble, meaning that it’s stored in fat cells and the body has a harder time removing it from the system (unlike most vitamins which are water soluble). Consuming too many vitamin D supplements over a prolonged period of time can lead to an increase in calcium build up in the body (hypercalcaemia). I’ll spare you the details but essentially, it can lead to kidney damage, weaken bones and harm the heart. Try not to exceed 100 micrograms (4000 IU) each day and you’ll be absolutely fine. This applies to all adults. Kids aged 1-10 years shouldn’t consume more than 50 micrograms (2000 IU) and infants under 12 months shouldn’t have more than 25 micrograms (1000 IU) each day. Fun for the whole family.
“How do I know if I’m not getting enough vitamin D? Who’s most at risk of deficiency?”
A vitamin D deficiency may sometimes produce no symptoms or take a long time to manifest. Some symptoms include depression, bone pain, weakness and muscle aches.
In terms of who’s at risk, some people won’t make enough vitamin D from sunlight because they don’t go outside. This could be because they’re frail, they may wear clothes that cover up most of the skin or they might have dark skin. If this is you or someone you know, taking a daily supplement containing 10 micrograms of vitamin D all year round can help.
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Dr Zobir Alexander, MB ChB, BSc (Hons) - Senior writer