Key points
- Vitamin D is made in the skin when UVB from sunlight reaches it. In the UK, UVB is strong enough for this roughly from late March to the end of September.
- NHS guidance is 10µg, or 400 IU, a day. Everyone is advised to consider a supplement through autumn and winter. Some groups are advised to take one year round.
- Those groups include people who spend little time outdoors, people who cover most of their skin when outside, and people with dark skin, who may not produce enough from UK sunlight even in summer.
- The upper limit for adults is 100µg a day. Vitamin D is fat-soluble and accumulates in the body, so higher intakes are worth discussing with a GP or practitioner rather than assumed to be better.
- Sunscreen reduces UVB reaching the skin in laboratory conditions. In everyday use, where it is applied thinly and unevenly, the effect on vitamin D status appears to be much smaller. Sun protection still comes first.
- Vitamin D contributes to the normal function of the immune system, the maintenance of normal bones, teeth and muscle function, and to normal absorption and utilisation of calcium and phosphorus.
When the sun finally comes out, it's tempting to think you are getting all the Vitamin D you need just by being outside. But is that true?
While summer sun can support your body’s production of vitamin D, the full picture is a little more…shaded. Here’s why it might still be worth keeping that supplement in your daily routine, even in July.
Vitamin D: The Sunshine Nutrient
Vitamin D contributes to:
• Normal immune system function
• The maintenance of bones and teeth
• Normal muscle function
• Support for mood and general well-being
Your body produces vitamin D naturally when UVB rays from sunlight reach your skin. But there are a few caveats.
Can Sunscreen Use Reduce Your Body’s Vitamin D Synthesis?
Sun safety is essential, but it comes with a trade-off. Sunscreen with SPF 30+ can block up to 95%-98% of UVB rays, which means your body may not produce much vitamin D, even on sunny days.
This does NOT mean skip sunscreen, just be aware you might need a supplement.
Are You Getting Enough Sunlight Living Indoors?
Even in summer, many people spend most of their time indoors, working, commuting, caring for children or avoiding peak UV hours. If your skin isn’t getting direct sun exposure, your vitamin D production may be limited.
So if you’re working in an office, avoiding the heat or simply love the shade ( no judgment), you might still benefit from a supplement.
How Much Do Location and Skin Tone Impact Your Vitamin D Status?
People living in northern latitudes may not get enough UVB exposure for adequate vitamin D synthesis, even during summer months.
Individuals with darker skin tones have more melanin, which can reduce the skin’s ability to produce vitamin D from sunlight. As a result, they may require more consistent dietary or supplement intake.
Is Vitamin D Deficiency a Concern Even in Sunny Seasons?
Surprisingly, vitamin D deficiency is still common during summer. Many people start the season with low levels from winter, and a few sunny weekends aren’t always enough to replenish stores.
Should You Keep Supplementing in Summer?
For many people, the answer is yes, especially if you:
• Wear sunscreen regularly
• Spend a lot of time indoors
• Have a darker skin tone
• Live in a northern climate
• Want to support consistent immune, muscle or bone health
NHS guidance is 10µg, or 400 IU, of vitamin D a day. That applies year round for anyone in the groups above, and through autumn and winter for everyone else. The upper limit for adults is 100µg a day, so more is not automatically better: vitamin D is fat-soluble and accumulates in the body rather than being flushed out. Higher-strength products exist and have their place, but they are worth discussing with a GP or practitioner rather than choosing by the number on the label.
Get Your Sunshine Safely
You can enjoy the sun and support your health with a vitamin D supplement that fits your lifestyle. Look for:
• Vitamin D3 (cholecalciferol) is the active form preferred by the body
• Formulations with Vitamin K2 - for added support with bone health
• Convenient forms like liquid drops or easy-to-take capsules
