Over the last two decades researchers have tried to untangle a tricky question: can modest sun exposure reduce the risk of certain internal cancers while also increasing the risk of skin cancers? Possibly yes for some cancers, but the relationship is complex, dependent on dose, timing, skin type and other factors and it does not mean reckless tanning is safe. Several ecological and cohort studies find that regions or people with higher sun exposure and higher blood levels have lower incidence or mortality for some cancers. That has spurred hypotheses that sunlight largely via vitamin D production helps protect cells and the immune system. But observational studies can't prove cause-and-effect.
Newer approaches show signals that sunlight or higher vitamin D could reduce risk for particular cancers but the verdict isn't final. This area remains active research territory. Sunlight is a major risk for skin cancer. High and intermittent intense UV exposure (sunburns) and indoor tanning are clearly linked to higher melanoma and non-melanoma skin cancer risk. So any advice on “get more sun to reduce cancer risk” must be balanced against the well-proved harms of too much UV.
How might sunlight protect against internal cancers?
- Vitamin D production: UVB in sunlight converts skin precursors into vitamin D, which modulates cell growth, programmed cell death and immune responses, all relevant to cancer biology.
- Other sunlight effects: Sunlight may influence circadian rhythms, nitric oxide release which affects blood pressure and immune function and local skin-produced hormones.
- But remember, low vitamin D may sometimes be a marker of poor health rather than its cause. That is why high-quality trials are needed before declaring a simple “sun cures cancer” message.
Advice for safe sun exposure
If you want to gain possible health benefits of sunlight without unduly raising skin-cancer risk, follow a cautious plan:
1. Aim for short, regular exposures not long sunbathing sessions
For many people, brief exposure of arms and face. For example 10–30 minutes, 2–4 times a week, during non-peak hours can raise vitamin D. Amount varies with skin tone, season, latitude and age. Darker skin needs more time; older adults make less vitamin D. Avoid midday sun in hot months if it causes burning.
2. Avoid sunburn at all costs
Sunburns especially in childhood are a major risk for melanoma. If a session will cause redness or blistering, stop immediately and protect the skin.
3. Use sunscreen when you'll be out long enough to burn
Proper sunscreen use prevents sunburn without meaningfully blocking vitamin D in real-world use; sunscreen effectiveness at preventing squamous cell carcinoma is supported in trials. Apply correctly and reapply after swimming/sweating.
4. Expose larger skin areas occasionally
Exposing more skin briefly, for instance forearms and lower legs increases vitamin D synthesis compared with face-only exposure but balance this with sun safety to prevent burns.
5. Consider supplements if risk is high or sun exposure is limited
People at high risk for skin cancer, those living at high latitudes, vegetarians/vegans, older adults, and those who can't get safe sun should check vitamin D levels and consider supplementation as advised by a clinician.
6. Get regular skin checks and cancer screening
Sun protection doesn't replace skin surveillance. See a dermatologist for suspicious moles and follow population cancer-screening recommendations, e.g., colorectal screening, breast screening, relevant to your age and risk.
7. Sunlight has both risks and potential benefits
Evidence suggests sun exposure may be linked to lower risk or better outcomes for certain internal cancers but the data is mixed and causality isn't established for every cancer type. The safest, pragmatic approach is short, regular, non-burning sun exposure combined with sensible sun protection, dietary sources or supplementation of vitamin D when needed, and routine health screening. That way you can aim for the possible long-term benefits without paying the immediate price of sun damage.
Disclaimer: This content including advice provides generic information only. It is in no way a substitute for a qualified medical opinion. Always consult a specialist or your doctor for more information. NDTV does not claim responsibility for this information.
References
Benefits and Risks of Sun Exposure to Maintain Adequate Vitamin D Levels. — NCBI / NIH — 2023.
Vitamin D and Cancer: An Historical Overview of the Epidemiology and Mechanisms. — NCBI / NIH — 2022.
Vitamin D3 for reducing mortality from cancer and other causes: meta-analysis of RCTs. — NCBI / NIH — 2022.
Melanoma Epidemiology and Sun Exposure. — NCBI / NIH — 2020.
A causal analysis of the relationship between exposure to sunlight and colorectal cancer risk. — NCBI / NIH — 2024.
