Vitamin D deficiency affects a substantial portion of the UK population during the autumn and winter months, when UV-B radiation levels are too low for our bodies to make enough vitamin D naturally.
At Royal Oak Health, we’ve developed a comprehensive vitamin D portfolio to address the unique nutritional demands of the UK’s winter climate, with each formulation engineered to provide complete seasonal coverage.
The Clinical Case for Winter Vitamin D Supplementation
This seasonal drop in vitamin D production can have measurable impacts on multiple physiological systems. Key health implications include:
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Bone health optimisation – Vitamin D facilitates calcium absorption and bone mineralisation, supporting structural integrity.
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Immune system modulation – Adequate vitamin D levels are linked with enhanced immune response and reduced susceptibility to respiratory infections.
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Musculoskeletal function – Sufficient vitamin D supports muscle strength and balance, particularly important for older adults.
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Neurological wellness – Research indicates correlations between vitamin D status and cognitive function and mood regulation.
Understanding IU – What It Means
You’ll often see vitamin D doses described in IU, which stands for International Units. This is a standardised measure of the biological activity of vitamins and hormones.
For vitamin D:
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1 microgram (µg) = 40 IU
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1000 IU = 25 µg
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2000 IU = 50 µg
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5000 IU = 125 µg
Using IU helps you compare potency across products regardless of how the label is written.
How Much Vitamin D Do We Need in Winter?
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Public Health England notes that higher doses such as 25 µg/day (1000 IU) are acceptable for adults who want more robust coverage in autumn/winter (PHE/NICE Statement).
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Higher intakes (2000–3000 IU/day) are often used for people at greater risk of deficiency or to maintain optimal blood levels.
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5000 IU/day is considered a high dose used for deficiency correction under professional supervision; baseline and follow-up blood tests are recommended before long-term use (NHS).
Our Vitamin D Range – Tailored to Your Needs
Our vitamin D range reflects evidence-based dosing protocols and optimal delivery systems.
Vitamin D3 1000 IU Softgels – Enhanced Maintenance for Winter
Ideal for people with limited sun exposure or indoor lifestyles who want reliable winter coverage. Oil-based softgels support better absorption.
Vitamin D3 2000 IU Softgels – Robust Maintenance for Higher-Risk Adults
For adults wanting a solid evidence-based winter dose. 2000 IU daily supplementation aligns with public health recommendations for maintaining healthy vitamin D status in higher-risk individuals. A single bottle provides 6-month winter coverage. Also available in 360-count bottles for annual programmes or multi-user households.
Vitamin D3 + K2 Combination (3000 IU) – Elevated Seasonal Support with Cardiovascular Benefits
Designed for individuals with limited sun exposure or increased seasonal requirements. Combines vitamin D3 with vitamin K2 (menaquinone-7) to optimise calcium utilisation and support cardiovascular health through improved calcium trafficking.
Shop > £8 for high-level vitamin D coverage for 3 months, protecting you through the peak of winter.
Vitamin D3 + K2 High-Potency (5000 IU) – Deficiency Correction Under Professional Supervision
A high-dose option for deficiency correction or populations with minimal UV exposure. 5000 IU/day (125 µg/day) is considered a high dose. The inclusion of K2 supports safe calcium metabolism at higher vitamin D intakes.
Multivitamins Are Great, But Don’t Rely on Them for Vitamin D Alone
Our Multi Vitamins and Minerals range provides comprehensive daily support, containing 14 vitamins, 8 minerals (including vitamin D), and Lutein. It’s perfect for supporting immunity, energy, bone health, and overall wellness.
However, most multivitamins only contain modest amounts of vitamin D—usually around 5–10 µg (200–400 IU) per day. While this contributes to your overall intake, it may not be sufficient to meet your winter needs, especially in the UK when sunlight is limited.
That’s why many people take vitamin D separately, at doses of 1000–5000 IU depending on lifestyle, risk factors, and professional guidance. Combining a multivitamin with a targeted vitamin D supplement ensures both broad nutritional support and reliable winter coverage.
By understanding IU, choosing the correct dose, and combining targeted vitamin D with a multivitamin, you can protect your health throughout the winter months with confidence.
