Vitamin D and Your Health; Why It Matters More in Winter
- JDR nutrition
- Oct 3
- 2 min read
What is Vitamin D and why is it important?
Vitamin D is often called the “sunshine vitamin” because our bodies produce it when skin is exposed to sunlight. But Vitamin D is not just a vitamin – it acts like a hormone, influencing hundreds of processes in the body.
Vitamin D's main roles include:
Supporting bone strength by helping us absorb calcium and phosphorus.
Regulating the immune system, reducing susceptibility to infections.
Supporting mood and mental wellbeing – low levels are linked with seasonal affective disorder (SAD).
Helping regulate insulin sensitivity and blood sugar balance.
Supporting muscle strength and cardiovascular health.
Whose health is most at risk of Vitamin D deficiency?
Certain groups are particularly vulnerable:
People who spend little time outdoors or cover their skin for cultural reasons.
Individuals with darker skin tones (as melanin reduces Vitamin D production).
People who are overweight or obese (Vitamin D is fat-soluble and can be “trapped” in fat tissue).
Older adults, as skin becomes less efficient at producing Vitamin D.
Babies and young children, who need Vitamin D for growth and bone development.
How to test your Vitamin D levels
If you suspect your Vitamin D levels are low, for example, if you experience low mood, frequent infections, bone or muscle aches, or persistent fatigue, you can ask your GP to test Vitamin D with a simple blood test. Private finger-prick tests are also available and provide a reliable reading.
Food sources of Vitamin D
Vitamin D is found naturally in only a few foods, such as:
Oily fish (salmon, sardines, mackerel, herring).
Egg yolks.
Liver.
Fortified foods (some cereals, dairy alternatives, and spreads).
Diet alone is rarely enough to meet needs, particularly in winter.
Supplementation guidance, to boost Vitamin D for winter health
Adults: The NHS recommends 400 IU (10 µg) Vitamin D daily as a minimum. In practice, many adults benefit from 1,000–3,000 IU daily through winter.
Children:
Babies (if breastfed) should have 8.5–10 µg Vitamin D daily from birth.
Children aged 1–4 should be given 10 µg Vitamin D daily.
Children over 5 are advised to take a Vitamin D supplement during autumn and winter.
What about Vitamin K2?
Vitamin D helps us absorb calcium, but Vitamin K2 directs calcium into bones and teeth, rather than allowing it to build up in arteries.
Supplementing with K2 with Vitamin D can be beneficial, especially if dietary intake is low.
Good sources include cheese, butter, egg yolks, and fermented foods.
Key takeaway
Vitamin D deficiency is common in the UK, especially in the winter months. Testing is simple, supplementation is effective, and addressing deficiency can make a remarkable difference to immunity, mood, and energy.
If you’re concerned about your Vitamin D status or want help choosing the right supplement for yourself or your family, click here to book a free health chat...
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