The Sunshine Hormone You're Probably Running Low On
Why vitamin D matters far beyond your bones — and why so many of us don't get enough.
nutrition
Vitamin D isn't really a vitamin in the way we usually think of one. It behaves more like a hormone — your skin makes it from scratch when sunlight hits it, and your liver and kidneys then have to activate it in two separate steps before your body can actually use it. That's a more involved supply chain than almost any other nutrient you eat, which is part of why it goes wrong so easily and so quietly.
How it's actually made. UVB rays hitting bare skin start the process. From there, the liver converts it into 25-hydroxyvitamin D — the form measured in a blood test — and the kidneys convert that into its final active form. A break anywhere along that chain, not just 'not enough sun,' can leave you deficient.
Why it's so common. Living above roughly 37° latitude — which includes all of Bulgaria — means winter sunlight is often too weak to trigger meaningful production, no matter how much time you spend outside. Darker skin, sunscreen, older age, and simply spending most daylight hours indoors all compound the same problem.
Bones and muscles — the classic story. Vitamin D drives and absorption, so low levels show up as bone aches, muscle weakness, and cramping. This is also the symptom picture most often mistaken for fibromyalgia or chronic fatigue syndrome, since the pain is diffuse and doesn't point anywhere specific.
Immune function and mood — the less obvious story. Vitamin D receptors sit on immune cells too, which is part of why deficiency tracks with getting sick more often. Low levels have also been linked to low mood and seasonal affective disorder, particularly through the darker months.
Getting it back, sensibly. Short midday sun exposure helps for many people, though it depends heavily on skin tone, latitude, and season. Vitamin D3 (from animal sources or supplements) raises blood levels more effectively than D2 (the plant-based form). Fatty fish and egg yolks help, but realistically, food alone rarely closes a real deficiency — this is usually where testing and a doctor's guidance matter more than guessing.
The tricky part about this particular deficiency is that it rarely announces itself clearly. Fatigue, aches, low mood, catching every cold that goes around — each of those has a dozen possible explanations, so vitamin D is easy to overlook until a blood test actually names it. If any of this sounds familiar, the honest first step isn't more sunlight or a bigger supplement dose — it's finding out your actual number.
Your homepage already shows you the day's weather — worth glancing at not just for an umbrella, but as a quiet reminder of how much real sun exposure a stretch of cloudy days has actually left you.
Vitamin D is fat-soluble, which means — unlike vitamin C or the B vitamins — your body stores it, and taking large doses without knowing your levels can push you too high, not just too low. Get tested before you supplement seriously, and let a doctor guide the dose.