Summer arrives. We ditch the coats. The days get long, lazy, and golden. It feels like a health reset. A freebie. You step outside for a soccer kickabout, a beach nap, or just to feel that warmth on your skin. You assume your Vitamin D stores are refilling.
They probably aren’t.
Not really. And definitely not if you have dark skin, or if you are older, or if you live north of the equator where the sun stays shy.
A new study from Newcastle University in the UK just dropped in the European Journal of Clinical Nutrition. The findings are blunt: even in the peak summer months, most people remained dangerously low on Vitamin D.
Why the sun is lying to you
Here is the setup. Bernard Corfe, a nutrition researcher, led a team that tested 299 people. The timeline ran from the dead of winter in December 2024 straight through to the height of summer in August 2025. They used finger-prick tests. Simple.
The subjects? Half were over 65. The other half had darker skin tones. Both groups start out with a disadvantage in these Northern latitudes.
The results?
Among those 65 and older, 55 percent still fell below the recommended threshold in summer.
For adults with darker skin, the number hit 72 percent.
That’s not a “let’s get out more” problem. That’s a structural biology issue. The numbers barely budged as the calendar flipped from snowy January to sweaty July.
Corfe says it plainly: “Vitamin D levels didn’t improve… when we would usually expect them to recovery.”
Expectations, it seems, are the real problem.
Three reasons your skin isn’t a factory anymore
Vitamin D is weird. Unlike every other vitamin, your body makes it. Your skin uses Ultraviolet B (UVB) rays as fuel.
In theory, summer = more UVB = happy bones.
In practice, three things get in the way.
- Age. Your skin gets thinner, less efficient. It just stops listening to the sun. Plus, older adults spend less time outdoors generally. Double whammy.
- Melanin. This is the pigment that gives skin its color. It is brilliant. It protects against cancer, against damage. It blocks UV rays like a force field. The trade-off? People with darker skin need significantly more exposure to synthesize the same amount of Vitamin D as lighter skin. The natural sunscreen works too well for vitamin production.
- Geography. You can’t cheat physics. Northern Britain sits at a latitude where the angle of the sun is weak for months on end. Even summer UVB can be insufficient.
Is it safe to just lay there longer?
Some people think: “Okay, if 72% are deficient, I’ll just tan longer.”
Do not do that.
Researchers looking at sunny Spain offer a cautionary tale. To get adequate Vitamin D in July in Valencia, you’d need to sit in noon sunlight for 7 minutes. Sounds easy. Right?
Except it is 38°C (100°F+) in the shade.
Sunbathe long enough to fix your blood work, and you might get sunstroke or burns. It is uncomfortable. It is potentially dangerous. The math on skin cancer risk usually loses against the benefits of a quick blast, unless you are trying to treat severe deficiency without supplements.
Then there is the winter comparison. In the same Spanish locale, meeting requirements in winter requires 2 hours a day of exposure. Nobody does that. Nobody wants to.
The supplement reality check
This brings us to the uncomfortable truth the authors highlight: for high-risk groups, sunshine alone is a myth.
“You can’t assume that spending more time outside in summer will solve the problem,” Corfe warns.
The solution? Supplements. Year-round ones.
A critical nuance here: every single person in this study had low Vitamin D at the start. Everyone who already took supplements was kicked out of the trial. So, the 72 percent figure doesn’t mean 72% of all Black Britons are deficient right now. It means those who rely only on food and sun are in deep trouble.
But the direction is clear. UK guidance already pushes a 400 IU daily dose for everyone over age 4 from October to March. The researchers are pushing for a rethink. Why stop in April?
In the US, the rules differ.
– Children and adults: 600 IU
– Over 70s: 800 IU
Don’t overdo it
A warning. Vitamin D is fat-soluble.
Water-soluble vitamins like C or B? Your pee carries away what you don’t use. Harmless. Mostly.
Vitamin D stores up. It accumulates. If you chug massive doses because you “want to be super healthy,” you can hit toxicity levels. Hypercalcemia is no joke. It damages kidneys and blood vessels.
The funding source also merits a glance. The study was paid for by BetterYou Ltd, a supplement company. That doesn’t automatically mean the data is fake—scientific journals have editors—but it means the narrative favors the pill over the beach.
Is that bad?
For someone in Manchester or Glasgow or New York during the shorter days, probably not. The sun is weak. Your skin is slow. The bottle on the counter is reliable.
We keep treating summer like a cure. It isn’t. Not for everyone. And pretending otherwise might leave us walking into autumn with brittle bones.
