Does sunscreen block vitamin D production? This common concern often leads people to question whether sun protection might compromise their vitamin D status. Whilst sunscreens are designed to filter ultraviolet B (UVB) radiation—the same wavelengths that trigger vitamin D synthesis in the skin—real-world evidence suggests that typical sunscreen use does not cause clinically significant vitamin D deficiency in most people. In the UK, where seasonal sunlight is limited and skin cancer rates continue to rise, understanding how to balance effective sun protection with maintaining adequate vitamin D levels is essential for long-term health.

How Sunscreen Affects Vitamin D Production

Sunscreen does have the potential to reduce vitamin D synthesis in the skin, though the relationship is more nuanced than many people realise. Sunscreens work by absorbing, reflecting, or scattering ultraviolet (UV) radiation, particularly UVB rays, which are the same wavelengths responsible for triggering vitamin D production in the epidermis. Laboratory studies have demonstrated that when applied at the recommended thickness (2 mg/cm²), high sun protection factor (SPF) sunscreens can theoretically block up to 95–98% of UVB radiation, which would significantly impair cutaneous vitamin D synthesis.

However, real-world evidence suggests that typical sunscreen use does not lead to clinically significant vitamin D deficiency in most populations. This apparent paradox occurs because people rarely apply sunscreen as thickly or as frequently as recommended in controlled studies. Research conducted in various settings, including the UK and Australia, has found that regular sunscreen users do not have substantially lower vitamin D levels compared to non-users when other factors are controlled. The incomplete coverage, delayed reapplication, and missed areas during typical application allow sufficient UVB exposure for some vitamin D production to occur.

It is important to note that individual factors significantly influence this relationship, including baseline vitamin D status, skin phototype, geographical latitude, season, and duration of sun exposure. People with darker skin, older adults, those with limited outdoor activity, and individuals living at higher latitudes (such as much of the UK) may be more vulnerable to vitamin D insufficiency, regardless of sunscreen use. The NHS, British Association of Dermatologists and UK Health Security Agency emphasise that sun protection (including sunscreen, shade, clothing and avoiding peak UV hours) remains essential for reducing skin cancer risk, whilst vitamin D requirements can be met through other strategies.

Understanding Vitamin D Synthesis and Sun Exposure

Vitamin D synthesis is a complex photochemical and metabolic process that begins in the skin upon exposure to UVB radiation (wavelengths 290–315 nm). When UVB photons penetrate the epidermis, they convert 7-dehydrocholesterol, a cholesterol precursor present in skin cells, into previtamin D₃. This compound then undergoes thermal isomerisation to form cholecalciferol (vitamin D₃), which enters the bloodstream and is transported to the liver. In the liver, vitamin D₃ is hydroxylated to 25-hydroxyvitamin D [25(OH)D], the major circulating form and the biomarker used to assess vitamin D status. A second hydroxylation occurs in the kidneys, producing the active hormone 1,25-dihydroxyvitamin D, which regulates calcium homeostasis, bone metabolism, and numerous other physiological processes.

The efficiency of cutaneous vitamin D synthesis depends on multiple variables. Skin pigmentation is particularly important: melanin absorbs UVB radiation, meaning individuals with darker skin (Fitzpatrick skin types IV–VI) generally require longer sun exposure to produce equivalent amounts of vitamin D compared to those with fair skin. Age also plays a role, as the capacity for vitamin D synthesis tends to decline with advancing years; older adults may produce significantly less vitamin D than younger individuals for the same UV exposure.

Geographical and seasonal factors are especially relevant in the UK. At latitudes above 50°N (which includes most of Scotland and northern England), the angle of the sun during winter months (October through March) means that insufficient UVB radiation reaches the earth's surface for adequate vitamin D synthesis, regardless of sun exposure duration. Even in summer, factors such as cloud cover, air pollution, and time spent indoors significantly limit opportunities for vitamin D production. This seasonal variation explains why the NHS and UK health authorities recommend that everyone in the UK consider vitamin D supplementation during autumn and winter months.

Balancing Sun Protection with Vitamin D Needs

Achieving an appropriate balance between adequate sun protection and maintaining vitamin D sufficiency requires a personalised, evidence-based approach. The primary principle endorsed by UK health authorities is that sun protection should not be compromised in pursuit of vitamin D, as the risks of excessive UV exposure—including melanoma, non-melanoma skin cancers, photoageing, and exacerbation of certain photosensitive conditions—substantially outweigh the benefits of unprotected sun exposure for vitamin D synthesis.

For most individuals in the UK, brief, incidental sun exposure to the face, arms, and hands during daily activities is often sufficient for some vitamin D production during spring and summer months. The concept of a 'safe' duration varies considerably depending on skin type, time of day, and UV index. Fair-skinned individuals may synthesise vitamin D more quickly than those with darker skin, but there is no official recommendation to seek unprotected sun exposure specifically for vitamin D production.

Practical strategies for balancing these considerations include:

• Applying broad-spectrum sunscreen (SPF 30 or higher) before going outdoors to areas at risk of sun damage

• Using sunscreen as part of a comprehensive approach including seeking shade, wearing protective clothing, and avoiding peak UV hours (11:00–15:00)

• Timing outdoor activities during periods of lower UV intensity (before 11:00 or after 15:00) when appropriate

• Taking care never to burn, regardless of vitamin D considerations

• Monitoring individual vitamin D status through blood testing if at higher risk of deficiency or symptomatic (not as routine screening)

Certain populations require particular attention, including pregnant and breastfeeding women, infants and young children, older adults, individuals with limited mobility or sun exposure, those with darker skin living in the UK, and people with conditions affecting vitamin D metabolism. For these groups, supplementation is often more reliable and safer than attempting to obtain vitamin D through sun exposure.

It is important to note that sunbeds should never be used as a way to boost vitamin D levels, as they emit harmful UV radiation and increase skin cancer risk.

UK Guidelines on Sunscreen Use and Vitamin D

UK health authorities, including the NHS, UK Health Security Agency, Office for Health Improvement and Disparities, and the British Association of Dermatologists, provide clear, evidence-based guidance on both sun protection and vitamin D adequacy. The official position is that sunscreen should be used as part of a comprehensive sun protection strategy, and that vitamin D requirements should be met primarily through diet and supplementation rather than unprotected sun exposure.

Regarding sunscreen use, UK guidelines recommend:

• Using a broad-spectrum sunscreen with SPF of at least 30 and high UVA protection (indicated by the UVA star rating of 4–5 stars or the UVA circle logo)

• Considering higher SPF (50+) for children and those at higher risk of sun damage

• Applying sunscreen generously (approximately 2 mg/cm² or about 6–8 teaspoons for an average adult body)

• Reapplying every two hours and after swimming, sweating, or towel drying

• Using sunscreen as one component of sun protection, alongside seeking shade, wearing protective clothing, and avoiding peak sun hours

For vitamin D, the NHS and Scientific Advisory Committee on Nutrition (SACN) recommend:

• All adults and children over one year should consider taking a daily supplement containing 10 micrograms (400 IU) of vitamin D, particularly during autumn and winter (October through March)

• Certain groups should take a daily supplement year-round: infants (receiving 8.5–10 micrograms daily from birth to one year if not consuming 500 ml of infant formula), people with limited sun exposure, those with darker skin, and individuals at risk of deficiency

• Pregnant and breastfeeding women should take 10 micrograms daily throughout pregnancy and whilst breastfeeding

There is no official guidance suggesting that people should reduce sunscreen use or seek unprotected sun exposure to maintain vitamin D levels. The Scientific Advisory Committee on Nutrition (SACN) reviewed the evidence extensively and concluded that the UK population cannot rely on sun exposure alone for adequate vitamin D, particularly given the country's latitude and climate. Healthcare professionals should reassure patients that appropriate sunscreen use, when combined with dietary sources and supplementation, allows for both skin cancer prevention and vitamin D sufficiency.

Alternative Sources of Vitamin D

Given the limitations of cutaneous vitamin D synthesis in the UK climate and the importance of sun protection, alternative sources of vitamin D are essential for maintaining adequate status. These sources fall into two main categories: dietary intake and supplementation.

Dietary sources of vitamin D are relatively limited, as few foods naturally contain significant amounts. The richest natural sources include:

• Oily fish (salmon, mackerel, sardines, herring): providing 5–25 micrograms per 100g serving

• Cod liver oil: approximately 25 micrograms per 5 ml teaspoon (note: pregnant women should avoid cod liver oil supplements due to vitamin A content)

• Egg yolks: about 1–2 micrograms per egg

• Wild mushrooms exposed to UV light: variable amounts of vitamin D₂

• Red meat and liver: modest amounts (0.3–1 microgram per serving) (note: pregnant women should avoid liver due to high vitamin A content)

In the UK, certain foods are fortified with vitamin D to help improve population intake. Fortified foods include:

• Infant formula (mandatory fortification)

• Some fat spreads and margarines (voluntary fortification; check labels)

• Some breakfast cereals (voluntary fortification)

• Some plant-based milk alternatives (voluntary fortification)

• Some yoghurts and dairy products (voluntary fortification)

However, even with a diet including these sources, it is challenging to obtain the recommended 10 micrograms daily from food alone, which is why supplementation is advised for most UK residents.

Vitamin D supplements are available in two forms: vitamin D₃ (cholecalciferol), derived from animal sources, and vitamin D₂ (ergocalciferol), derived from plant sources. Evidence suggests that vitamin D₃ is more effective at raising and maintaining 25(OH)D levels. Supplements are widely available over the counter in various formulations, including tablets, capsules, oral sprays, and liquid drops for infants. The standard recommended dose is 10 micrograms (400 IU) daily for most adults and children over one year.

Certain individuals may require higher doses under medical supervision, including those with malabsorption disorders (coeliac disease, Crohn's disease, cystic fibrosis), chronic kidney disease, obesity, or confirmed vitamin D deficiency. NICE Clinical Knowledge Summaries provide guidance on treating deficiency, typically involving loading doses followed by maintenance therapy. Patients should consult their GP if they suspect deficiency, particularly if experiencing symptoms such as bone pain or muscle weakness. Blood testing to measure 25(OH)D levels can confirm deficiency (typically defined as <25 nmol/L) or insufficiency (25–50 nmol/L), allowing for appropriate treatment. It is important to note that excessive vitamin D supplementation can lead to toxicity, though this is rare with standard doses and typically only occurs with very high intakes (>100 micrograms daily) over prolonged periods.

Patients who experience suspected side effects from vitamin D medicines should report them through the MHRA Yellow Card Scheme (yellowcard.mhra.gov.uk).

Frequently Asked Questions