Personal sun exposure and serum 25-hydroxy vitamin D concentrations

Area of Science:

• Dermatology
• Endocrinology
• Public Health

Background:

• Solar ultraviolet-B (UVB) radiation is crucial for vitamin D synthesis in the epidermis.
• Vitamin D plays a vital role in numerous physiological processes.
• Maintaining adequate vitamin D levels is a public health concern.

Purpose of the Study:

• To quantify the relationship between personal solar UV exposure and serum 25-hydroxy vitamin D (25[OH]D) concentration.
• To determine the optimal level of solar UV exposure for maximizing vitamin D levels in adults.

Main Methods:

• A study involving 207 South Australian adults aged 27-61 years.
• Blood samples were collected for serum 25(OH)D analysis.
• Participants completed a questionnaire recalling sun exposure over the preceding 16 weeks.
• Statistical modeling using multiple linear regression, controlling for age, sex, and BMI.

Main Results:

• Estimated erythemal solar UV exposure in the 6 weeks prior to blood collection was the strongest predictor of serum 25(OH)D.
• Serum 25(OH)D levels increased with personal solar UV exposure, plateauing at approximately 89 nmol/L.
• This maximum concentration was reached at an estimated mean weekly solar erythemal UV exposure of about 1230 mJ/cm².
• The maximum was consistent even after accounting for clothing coverage.

Conclusions:

• Personal solar UV exposure is a key determinant of serum 25(OH)D concentration in Australian adults.
• An average maximum serum 25(OH)D of approximately 89 nmol/L can be achieved through sun exposure.
• These findings have implications for public health recommendations regarding sun exposure and vitamin D sufficiency.