There is a classic summer illusion: as soon as temperatures rise above +25°C and a T-shirt replaces a jacket, the bottle of vitamin D automatically goes “on vacation” to the back of the drawer. The logic seems flawless: there is sun, so the body produces everything on its own.
But biology does not follow our summer plans. And this is where it gets interesting: even in the middle of July, many people still have a vitamin D deficiency. Yes, even those who think: “I get a tan, so everything is fine”.
Let’s break down why the sun is not always a guarantee and who should not stop supplementation in summer.
Why summer sun is not a “vitamin recharge”
For the body to produce vitamin D, it is not enough to simply be in the sun — it requires UVB ultraviolet rays. And this is where the nuances begin that completely destroy the myth “summer = enough vitamin D”.
SPF cream: protection that blocks synthesis
Sunscreen is a must-have of the modern lifestyle. It truly reduces the risk of skin aging and skin cancer. But it has a side effect that is often overlooked:
- SPF 15 blocks up to 93% of vitamin D synthesis
- SPF 30 — up to 97%
In other words, you protect your skin… but almost switch off the “vitamin factory”.
Office lifestyle
Modern summer often looks like this: home → car → office → car → home.
The peak sunlight hours (11:00–15:00) are spent under artificial lighting and air conditioning. UVB rays do not pass through glass. So sitting by a window is comfortable, but it does not support vitamin D synthesis.
“Safe sun” is not a solution either
Morning and evening hours are correct from a dermatological point of view. But there is a catch: at these times the sun is low, and UVB rays are almost inactive.
Result:
when it’s safe — it’s ineffective,
when it’s effective — it’s risky.
Urban air as a filter
Smog, dust, and cloud cover in big cities act as a natural “screen”. A portion of ultraviolet radiation simply does not reach the skin. And you may not even notice it: you can still tan, but vitamin D synthesis remains minimal.
Who sunlight is not enough for
There are groups of people for whom summer does not guarantee adequate vitamin D levels:
Darker skin
Melanin protects against sun exposure but slows down vitamin D synthesis. More time in the sun is needed for the same effect.
Age 50+
With age, the skin’s ability to produce vitamin D decreases by 3–4 times.
Overweight individuals
Vitamin D is fat-soluble: it gets “stored” in fatty tissue and enters the bloodstream less efficiently.
Children, pregnant and breastfeeding women
They have higher needs, which increases the risk of deficiency.
Take it or not in summer: the key point
The biggest mistake is not taking vitamin D, but doing it or stopping it blindly.
Deficiency does not appear immediately. It works silently:
- chronic fatigue
- weakened immunity
- joint pain
- low mood and “brain fog”
In summer, this is often blamed on heat, work, or lack of sleep.
Smart approach instead of guessing
The only correct strategy is diagnosis, not intuition.
- Blood test for 25(OH)D
- Assessment of the real level
- Dosage adjustment with a doctor
Only after that is a decision made: continue or adjust supplementation in summer.
