How do you get vitamin D?

Vitamin D is essential for supporting bone health, muscle function and the immune system.¹ You may have heard it described as the ‘sunshine vitamin’ since it’s well known that getting out in the sunshine helps your body to produce vitamin D – but how exactly does this work? And, what can you do during the winter months to keep your vitamin D levels up when the sun is less powerful?

Below, we explore the link between vitamin D and the sun, as well as highlighting potential alternative sources to ensure you get enough vitamin D even during the winter. Keep reading to learn more.

How do you get vitamin D from the sun?

Vitamin D production starts when the skin is exposed to ultraviolet B (UVB) rays from sunlight. These rays trigger a chemical reaction in the skin, converting a cholesterol derivative into previtamin D3, which the body then transforms into vitamin D3 (cholecalciferol).¹ Several factors influence how much vitamin D your body can make, including geographic location, skin tone, time of year and the amount of sun exposure you get.

Short periods of sun exposure—generally 10 to 30 minutes a few times per week for fair-skinned individuals—are often enough to produce sufficient vitamin D during the summer months. People with darker skin tones have more melanin, which acts as a natural barrier against UVB rays. While this protects the skin from sun damage, it also reduces vitamin D production, meaning more time in the sun may be needed.²

Vitamin D is a fat-soluble vitamin, which means your body can store it and does not require daily sun exposure to maintain adequate levels. A cloudy day or a missed session in the sun is unlikely to have a major effect, but prolonged lack of exposure over weeks or months can lead to deficiency.

Season and latitude also play a role. In northern parts of the UK, such as Scotland, the angle of the sun in autumn and winter is too low for the skin to synthesise enough vitamin D. This is less of an issue in southern areas, where limited winter sun may still contribute slightly, but supplementation or dietary sources can be helpful during these months. For those who travel to sunnier destinations in winter, short sun holidays can temporarily boost vitamin D levels, though relying on this alone may not fully maintain optimal status throughout the colder months. Understanding these seasonal, geographic and storage factors can help people manage their vitamin D intake and avoid deficiency.

Does sunscreen block vitamin D?

Sunscreen helps protect the skin from harmful UV radiation, and it does reduce the amount of UVB that reaches the skin.³ However, even when using sunscreen, some UVB rays can still penetrate, so vitamin D production is not completely blocked. Lower-strength sunscreens, such as SPF 15, allow more UVB through than higher SPF products, meaning small amounts of vitamin D can still be synthesised.³

Balancing sun safety with vitamin D needs is important. Brief periods of unprotected sun exposure, followed by proper use of sunscreen for longer time outdoors, can help maintain vitamin D levels while reducing the risk of skin damage.

Can you receive vitamin D through a window?

Vitamin D production in the body depends on direct exposure to ultraviolet B (UVB) rays from sunlight.² Most types of glass, including the windows in homes, offices, and cars, block nearly all UVB radiation. This means that even if you are sitting by a sunny window, your skin is not able to produce vitamin D. While sunlight streaming through glass can provide warmth and bright light, it cannot substitute for direct sun exposure when it comes to making this essential nutrient.

For people who spend the majority of their time indoors, this can be an important consideration. Office workers, students, or those who stay home most of the day may not get enough UVB exposure to maintain adequate vitamin D levels, especially during the autumn and winter months or in locations at higher latitudes where sunlight is weaker.

In such cases, relying on dietary sources or supplements becomes key. Foods rich in vitamin D, such as oily fish, fortified dairy products, and egg yolks, can help fill the gap. For some individuals, particularly those with limited sun exposure or higher needs, taking a vitamin D supplement under the guidance of a healthcare professional can ensure levels remain sufficient year-round.

Do sunbeds give you vitamin D?

Sunbeds do give off UV radiation, mainly UVA, with just a small amount of UVB that your body could use to make vitamin D.³ However, the truth is that any potential boost in vitamin D comes with a significant risk. Using sunbeds regularly increases the chance of skin damage and skin cancer, which is why health experts, including the British Association of Dermatologists, strongly advise against relying on them for vitamin D.

If you’re looking to maintain healthy vitamin D levels, it’s much safer to focus on short periods of natural sunlight, fortified foods, or supplements. These options provide the benefits without putting your skin at unnecessary risk.

Can you get vitamin D from food?

While sunlight is the primary source of vitamin D, diet can help to support levels, particularly in periods of low sun exposure. Fatty fish, eggs and fortified foods such as cereals and plant-based milk can provide vitamin D. 

For those who cannot achieve adequate levels through sunlight and food alone, supplementation is a safe and effective option. Nutraxin’s Vitamin D3 + K2 tablets are designed to support daily intake and maintain healthy vitamin D levels throughout the year.

Maintaining adequate vitamin D levels is essential for overall health. Short, safe periods of sun exposure, a balanced diet and supplementation when needed can help to support normal bone health, muscle function and immunity.¹ Understanding how sunlight, dietary intake and lifestyle factors interact allows individuals to manage their vitamin D status effectively throughout the year.

References 

1. Great Britain Nutrition and Health Claims Register. (2024). Authorised nutrition and health claims. Available at: https://www.gov.uk/government/publications/nutrition-and-health-claims-great-britain-register
   
2. Holick, M. F. (2007). Vitamin D deficiency. New England Journal of Medicine, 357(3), 266–281.
3. British Association of Dermatologists. (n.d.). Sunbeds and skin cancer. Available at: https://www.bad.org.uk/for-the-public/skin-cancer/sunbeds