The sun paradox: vitamin D, photodamage, and sensible choices

During a consultation with a dermatologist, vitamin D often sparks an uncomfortable conversation: on the one hand, we know that the skin can synthesize it with UVB radiation; on the other, that same sun exposure—especially if it results in tanning or sunburn—increases photodamage and the risk of skin cancer. Between «it’s natural to get some sun» and «avoid the sun at all costs,» there’s a middle ground: practical, evidence-based decisions to protect overall health without making your skin the price to pay.

UV radiation helps produce vitamin D, but it also damages DNA and increases the risk of skin cancer: the benefit does not outweigh the risk. IARC 1992

What is vitamin D and why does it matter?

Vitamin D functions like a hormone: it helps regulate calcium absorption and the maintenance of bone and muscle. The problem arises when it becomes a kind of «health catch-all» and it’s assumed that more is always better. The prudent interpretation today is this: there are solid reasons to prevent deficiency , but that doesn’t justify turning sun exposure (without protection) into «therapy,» nor normalizing high levels of supplementation without a clear reason. May 2024

Your skin can produce vitamin D when it’s exposed to sunlight (specifically UVB radiation). And here’s the crux of the problem: UV radiation (from the sun and artificial sources) produces acute effects like sunburn and DNA damage, and is associated with chronic effects like photoaging and skin cancer. WHO 2022 IARC 1992

So, what is the sensible strategy? (concrete steps)

There’s no single rule that works for all skin types, seasons, and latitudes. But there is a sensible plan.

Step 1: Change the target

• • Don’t seek to «sunbathe for vitamin D.» Seek outdoor life with reasonable protection , without intentional tanning and without sunburn.

  • If you are going to be exposed for a sustained period (sports, beach, mountains, outdoor work): prioritize shade, clothing, hat, glasses and sunscreen.

Step 2: Ensure vitamin D through consistent means

• • For most people, the most stable and controllable way to meet needs is through food + fortified foods + supplements if appropriate , especially when skin synthesis is unpredictable.

  • As a population reference, the recommended intakes were established assuming minimal sun exposure , precisely because of the variability in synthesis and the skin risk. Ross 2011

  • Avoid chronic megadoses without supervision: Vitamin D toxicity is usually related to excessive supplementation, not sun exposure. NIH SDGs 2025

Step 3: Decide if you need (25(OH)D) analysis based on context

• • Measuring 25(OH)D may be useful in people at clinical risk (osteoporosis, frailty, malabsorption, kidney/liver disease, certain medications, etc.). However, routine screening in asymptomatic adults has not shown clear benefits and is not generally recommended. USPSTF 2021 DeMay 2024

Common mistakes

1. Look for a “minimum daily amount of sun without sunscreen” as a universal rule.

2. “Compensate” between weekdays and weekends: little daily exposure and then get burned on Saturday.

3. Self-medicating with high doses «just in case» and maintaining them for months.

4. Using tanning beds as a shortcut.

Myths vs. Facts

Myth: “There is a ‘safe’ UV exposure that maximizes vitamin D without increasing the risk of cancer.”
Fact: There is no scientifically proven threshold for maximizing vitamin D without increasing skin risk; therefore, if vitamin D is needed, diet, fortified foods, or supplements are usually preferred. American Academy of Dermatology 2009

Myth: “Sunscreen causes vitamin D deficiency.”
Fact: Overall, the evidence suggests that sunscreen use does not significantly compromise vitamin D status under real-world conditions, and that other behaviors (shade/clothing, limited time spent outdoors) have a greater influence. Passeron 2019

Myth: “More vitamin D is always better.”
Fact: There are reasonable ranges; sustained excess can have adverse effects, particularly hypercalcemia associated with excessive supplementation. NIH SDGs 2025

Vitamin D is important for bone health; however, its «all-around» preventive benefits (immunity, cancer, heart health) are more uncertain than is sometimes reported. Ross 2011

When should I consult a dermatologist?

Consult a dermatology specialist if:

• You experience burns with blisters, severe pain, fever, or general malaise after sun exposure.

• You have photosensitivity (rashes in low light) or you take photosensitizing medication.

• There is osteoporosis, fragility fractures, malabsorption, kidney/liver disease, or clinical suspicion of deficiency.

• Are you pregnant, breastfeeding, elderly with little outdoor exposure, or have a history of hypercalcemia? (Supplementation should be individualized.)

• You notice changes in moles or new lesions that grow, bleed, or do not heal.

Frequently Asked Questions

Should I «sunbathe» if I’m worried about vitamin D?

• As a deliberate strategy, it’s usually not the wisest approach. If there’s a risk of deficiency, a manageable plan (diet/fortified foods/approved supplement) without unnecessarily increasing UV exposure is preferable.

When is it most difficult to produce vitamin D with sunlight?

• When UVB levels are low or actual exposure is limited (indoor work, winter, little time spent outdoors), it’s advisable to consider more consistent alternatives.

What level of vitamin D is “normal”?

• It is measured as 25(OH)D, but cut-off points vary between laboratories and guidelines. The important thing is to avoid clinically relevant deficiencies and to contextualize the result.

Do I need to have my vitamin D measured routinely?

• Generally, no. It is individualized according to risk factors or clinical suspicion.

Can I get vitamin D poisoning?

• It is uncommon due to sun exposure. The risk usually comes from sustained high-dose supplements.

Bibliography and sources

• National Institutes of Health, Office of Dietary Supplements. Vitamin D: Fact Sheet for Health Professionals [Internet] . Bethesda (MD): National Institutes of Health; 2025 [consultado 30 may 2026] . Available from: NIH Office of Dietary Supplements .
• National Institutes of Health, Office of Dietary Supplements. Vitamin D: Fact Sheet for Consumers [Internet] . Bethesda (MD): National Institutes of Health; 2022 [consultado 30 may 2026] . Available from: NIH Office of Dietary Supplements .
• World Health Organization. Ultraviolet radiation [Internet] . Geneva: World Health Organization; 2022 [consultado 30 may 2026] . Available from: World Health Organization .
• American Academy of Dermatology Association. Sunscreen FAQs [Internet] . Rosemont (IL): American Academy of Dermatology Association; 2025 [consultado 30 may 2026] . Available from: American Academy of Dermatology Association .
• American Academy of Dermatology Association. Vitamin D stats and facts [Internet] . Rosemont (IL): American Academy of Dermatology Association; sf [consultado 30 may 2026] . Available from: American Academy of Dermatology Association .
• Neale RE, Khan SR, Lucas RM, Waterhouse M, Whiteman DC, Olsen CM. The effect of sunscreen on vitamin D: a review . Br J Dermatol. 2019;181(5):907-915. doi:10.1111/bjd.17980.
• Demay MB, Pittas AG, Bikle DD, Diab DL, Kiely ME, Lazaretti-Castro M, et al. Vitamin D for the prevention of disease: an Endocrine Society Clinical Practice Guideline . J Clin Endocrinol Metab. 2024;109(8):1907-1947. doi:10.1210/clinem/dgae290.
• National Institute for Health and Care Excellence. Sunlight exposure: risks and benefits. NICE guideline NG34 [Internet] . London: NICE; 2016 [consultado 30 may 2026] . Available from: NICE .
• Cancer Council Australia. Vitamin D [Internet] . Sydney: Cancer Council Australia; 2026 [consultado 30 may 2026] . Available from: Cancer Council Australia .
• Tran V, Duarte Romero BL, Andersen H, Clarke M, Collins LG, Dawson T, et al. Effect of daily sunscreen application on vitamin D: findings from the open-label randomized controlled Sun-D Trial . Br J Dermatol. 2025;193(6):1128-1137. doi:10.1093/bjd/ljaf310.