The “Sunshine vitamin” and why you might be missing out
Vitamin D is often dubbed the “sunshine vitamin,” but don’t let the cheerful name fool you—deficiency is widespread, especially during the gloomy winter months. Our bodies mainly make vitamin D when ultraviolet B (UVB) rays from the sun hit our skin. In countries like the UK or Ireland, especially above cities like Manchester or Liverpool and throughout the winter, sunlight exposure just isn’t enough to meet our needs. According to epidemiological studies in France (and findings are similar across Northern Europe), nearly 80% of people have insufficient vitamin D levels during the winter, and 40 to 50% are clearly deficient.
Certain groups are especially at risk: older adults (who spend less time outdoors and produce less vitamin D through their skin), pregnant women, growing children, people with darker skin, and anyone living in urban areas or who just doesn’t see the sun all that much.
Vitamin D: Not just a vitamin, but a hormone superstar
Vitamin D is not your average nutrient. It acts more like a hormone, playing a fundamental role in how your body absorbs calcium for healthy bones, supports your immune system, regulates mood, and may even help stave off certain chronic illnesses. Think of vitamin D as a “key” that lets calcium into your bones or as the “conductor” guiding the orchestra of your immune system.
Foods rich in vitamin D (we’re looking at you, oily fish, egg yolks, and liver) generally don’t provide enough to hit your daily requirements—especially in winter. That’s why supplementation is often recommended once the sunshine dwindles.
The four subtle signs of a vitamin D deficiency
Here are the four most frequent signs linked to low vitamin D. They’re often subtle, easy to brush off, and can linger below the radar for months:
- 1. Unexplained fatigue: You wake up already tired, even after what should be a good night’s sleep. You have frequent energy slumps, feel like you’re running on empty, and nothing seems to explain it. Vitamin D is involved in the functioning of mitochondria—the “power plants” of your cells. A lack of vitamin D can lead to persistent muscle and general fatigue, often becoming chronic.
- 2. Achy bones and muscle cramps: You get a dull, nagging pain in your bones, especially in your legs, hips, or lower back. There may be recurring muscle cramps or a general feeling of weakness in your limbs. Vitamin D regulates the absorption of calcium, and when you’re deficient, your body may start pulling calcium out of your bones, causing pain and making your bones split. Meanwhile, your muscles need vitamin D to function properly—it’s a full team effort.
- 3. Repeat infections: You’re constantly catching colds, bronchitis, sore throats—if there’s a virus about, you seem to find it. Even minor infections seem to drag on forever. Vitamin D is a powerful modulator of the immune system. It boosts the production of antimicrobial peptides and helps manage inflammation. Without enough vitamin D, your natural defences take a hit. Studies have shown that regular supplementation can reduce the risk of respiratory infections, especially in people who are already running low.
- 4. Low mood and “Winter Blues”: Feeling more down, less motivated, or irritable? Dreading winter? Some call it “winter blues” or seasonal low mood. Vitamin D plays a part in making serotonin—the neurotransmitter for wellbeing and keeping your mood level. Not enough vitamin D is linked with a higher risk of depression, especially in older adults.
What should you do?
If you recognise several of these signs, talk to your doctor. A simple blood test can clear up any doubts. And in the meantime, remember: a few minutes of sunlight every day, eating plenty of oily fish, and the right supplement in winter can make all the difference for your energy and overall wellbeing.
