From the Guidelines
To minimize the risk of skin cancer while maintaining adequate vitamin D levels, it is recommended to avoid exposure to the sun during peak hours (10 a.m.–4 p.m.) and instead seek shade or use protective measures such as clothing, hats, and sunglasses 1. When considering ultraviolet (UV) radiation exposure, it's essential to weigh the benefits of vitamin D synthesis against the risks of skin cancer.
Key Considerations
- The timing of sun exposure should be adjusted based on skin type, location, and season.
- People with darker skin may need longer exposure times, while those with very fair skin should start with just 5-10 minutes.
- In summer months or locations closer to the equator, shorter exposure times are needed, while winter months in northern latitudes may provide insufficient UVB for vitamin D production regardless of time spent outdoors.
Protective Measures
- Use a broad-spectrum sunscreen with a sun-protection factor of >15 1.
- Wear clothing, hats, and sunglasses that protect the skin 1.
- Avoid sunlamps and tanning beds 1.
Balancing Benefits and Risks
According to the US Preventive Services Task Force, behavioral counseling interventions can moderately increase the use of sun-protective behaviors in children, adolescents, and young adults aged 10 to 24 years with fair skin 1. However, it's crucial to note that the USPSTF found inadequate evidence to determine the effect of counseling on the use of sun-protective behaviors in adults older than 24 years 1. Ultimately, the optimal time for UV radiation exposure is one that balances the need for vitamin D synthesis with the risk of skin cancer, and individuals should prioritize protective measures and seek shade during peak hours.
From the Research
Optimal Time for UV Radiation Exposure
The optimal time for ultraviolet (UV) radiation exposure is a topic of ongoing research, with various studies providing insights into the best times for sun exposure to maximize vitamin D production while minimizing the risk of skin cancer.
- The time of day and year can significantly impact UV radiation exposure, with factors such as latitude, time of day, and season influencing the spectra and fluence rates of UV radiation 2, 3.
- Studies suggest that the best time for sun exposure to optimize vitamin D synthesis while minimizing the risk of cutaneous malignant melanoma (CMM) is between 10 a.m. and 1 p.m. 2, or around noon 3.
- However, the optimal time for sun exposure may vary depending on the location and time of year, with a study in Saudi Arabia finding that the best times for vitamin D production were between 9:00 a.m. and 10:30 a.m., as well as after 2:00 p.m. until 3:00 p.m. during summer, and between 10:00 a.m. and 2:00 p.m. during winter 4.
- It is also important to consider the duration of sun exposure, with a study in Switzerland finding that exposure durations between erythema risk and 1000 IU vitamin D production varied between 9 and 46 minutes, and that daily doses of vitamin D (1000 IU) were not reachable in autumn and winter months without additional oral vitamin D supplementation 5.
- Additionally, a study highlighted the importance of sun exposure for overall health, suggesting that insufficient sun exposure may be responsible for a significant number of deaths and increased incidence of various diseases, and recommending that people living outside the tropics ensure they expose their skin sufficiently to the sun, while taking care to avoid sunburn 6.