J Korean Med Sci.  2020 Mar;35(8):e50. 10.3346/jkms.2020.35.e50.

Can Current Recommendations on Sun Exposure Sufficiently Increase Serum Vitamin D Level?: One-Month Randomized Clinical Trial

• Lee YM
• Kim SA
• Lee DH

• KMID: 2471055
• DOI: http://doi.org/10.3346/jkms.2020.35.e50

Abstract

BACKGROUND
Lack of sunlight exposure is the primary reason for the worldwide epidemic of vitamin D deficiency. Although recommended sunlight exposure guidelines exist, there is no evidence regarding whether current guidelines are optimal for increasing vitamin D levels among individuals with vitamin D deficiency.
METHODS
Sixty Korean adults aged 20-49 years with serum 25-hydroxyvitamin D (25[OH]D) levels of < 20 ng/mL were randomly assigned to three groups: sunlight exposure (n = 20), vitamin D supplementation groups (n = 20), and daily living (n = 20) for 1 month. The sunlight exposure group had sunlight exposure on 20% to 30% of their body surface areas for 30-60 minutes per day, 3 times a week during the summer season. Vitamin D supplementation was prescribed with 800 IU/day of vitamin D. The serum levels of 25(OH)D were measured at baseline and at 1-month follow-up examinations.
RESULTS
The largest change in serum 25(OH)D was observed among the vitamin D supplementation group (+3.5 ng/mL, P < 0.001). The sunlight exposure group showed a slight increase in serum 25(OH)D level, but the absolute increase was less than one-third that of the vitamin D supplementation group (+0.9 ng/mL, P = 0.043). Only two participants in the sunlight exposure reached serum concentrations of 25(OH)D ≥ 20 ng/mL at follow-up. The daily living group showed no difference in vitamin D levels (−0.7 ng/mL, P = 0.516).
CONCLUSION
Sunlight exposure was not sufficient to overcome vitamin D insufficiency or deficiency in the current study subjects. Effectiveness of current sunlight exposure guidelines among various populations should be reassessed in larger clinical studies. TRIAL REGISTRATION: Clinical Research Information Service Identifier: KCT0002671

Keyword

Vitamin D Deficiency; Sunlight Exposure; Vitamin D Supplementation; 25(OH)D; 1,25(OH)â‚‚D; Randomized Clinical Trial

MeSH Terms

Adult
Body Surface Area
Follow-Up Studies
Humans
Information Services
Seasons
Solar System*
Sunlight
Vitamin D Deficiency
Vitamin D*
Vitamins*
Vitamin D
Vitamins