Vitamin D isn't a vitamin. And you almost certainly don't have enough.
More than four in five Italians test below the optimal range, even in July. Here is what that costs you, and what to do about it.
Here is something most people don't know: vitamin D isn't a vitamin. It is a hormone.
Your body makes it from sunlight, and almost every tissue you own has a receptor for it: immune cells, brain, muscle, heart, bone. That is why, when it is low, you don't feel it in one place. You feel it everywhere.
And in Italy, four adults in five don't have enough of it. Even in July.
The Italian paradox.
Italy gets more than 2,600 hours of sunshine a year. So why do we have some of the highest deficiency rates in Europe?
A 2019 study in Nutrients found that 76% of Italian adults had vitamin D below 30 ng/mL in winter. By summer, more than 40% were still deficient. (Minisola et al., Nutrients 2019.)
The reason is geometry. UVB rays, the only ones your skin can actually use, reach you only when the sun is more than 35 degrees above the horizon. In Milan or Rome, between October and March, that never happens, not even at noon. And in summer, most of us spend daylight hours indoors anyway.
If you live north of Naples and you don't supplement, the odds are you are deficient right now. Season alone won't fix this.
What you are actually losing.
- Your immune system runs slower. More colds, more flu, a higher risk of autoimmune conditions.
- Your bones weaken quietly. Without vitamin D you can't absorb calcium properly, and bone density falls for years before a fracture tells you why.
- Your mood takes a hit. The brain has vitamin D receptors in the exact regions that make serotonin. Deficiency and depression travel together.
- Your muscles lose strength. Low vitamin D is one of the most common causes of unexplained weakness after 50.
- Your heart pays the price. A meta analysis in the European Heart Journal linked deficiency to 33% higher all cause mortality.
Why "in range" isn't enough.
Italian labs flag deficiency below 30 ng/mL. But 30 is a floor, not a goal. The clinical evidence on immunity, mood, and cardiovascular health points to an optimal window of 50 to 80 ng/mL.
Most of the people we test sit somewhere between 18 and 28. Technically deficient, on a report that usually goes uncommented.
What the right dose looks like.
Most deficient adults need 2,000 to 4,000 IU of vitamin D3 a day to reach the optimal window. But this is one of those numbers where guessing doesn't work: some people absorb beautifully and overshoot, others supplement for years and barely move.
The only honest answer is: test, supplement, retest after three months.
What to do now.
If you are a Rosa member, vitamin D is already in your panel, alongside D binding protein and your calcium to phosphate ratio, which tell us how well your body is actually using it. We tell you where you are, where you want to be, and how to get there. Then we check again.
If you are not a member yet, at least ask your doctor to add 25(OH)D to your next draw. It is a cheap test that changes conversations.
