Beta-carotene does not act as an optical filter in skin

Area of Science:

• Photodermatology
• Nutritional Biochemistry
• Skin Optics

Background:

• Beta-carotene (a carotenoid) has shown photoprotective effects in specific conditions like erythropoietic protoporphyria and UV-induced carcinogenesis in mice.
• Oral beta-carotene supplementation has a minimal effect on sunburn threshold in humans.
• The mechanism of beta-carotene's photoprotection, especially at sufficient skin concentrations, remains under investigation.

Purpose of the Study:

• To investigate the photoprotective properties of beta-carotene by assessing its concentration and optical effects in mouse skin.
• To determine if oral beta-carotene supplementation leads to sufficient skin absorption to provide a sunscreen effect.

Main Methods:

• SKH-HR1 albino hairless mice were fed beta-carotene supplemented diets for two or four weeks.
• Skin optical properties were analyzed using forward scattering transmission spectroscopy.
• Beta-carotene presence and absorption peaks in epidermis and whole skin were measured.

Main Results:

• Mice skin appeared visibly yellow after beta-carotene supplementation.
• Weak beta-carotene absorption peaks were detected in the epidermis but not in full-thickness skin.
• The measured absorbance was insufficient to provide significant photoprotection via radiation absorption.

Conclusions:

• Oral beta-carotene does not reach sufficient concentrations in the skin to act as a sunscreen by absorbing UV radiation.
• The observed photoprotective effects of beta-carotene in photosensitive conditions likely operate through mechanisms other than direct UV absorption in the skin.