From the Guidelines
Retinol is a form of vitamin A that plays a crucial role in vision, reproductive function, and cellular growth and differentiation, as evident from the espen micronutrient guideline published in Clinical Nutrition in 2022 1.
Key Functions of Retinol
- Retinol and its metabolite retinal are responsible for vision and reproductive function.
- Retinoic acid, another metabolite of retinol, controls cellular growth and differentiation, particularly in mucous membranes.
- Vitamin A, of which retinol is a precursor, acts as a prohormone, with its active metabolites binding to nuclear receptors to activate gene expression in over 500 target genes 1.
Importance of Retinol in the Body
- Retinol is essential for the immune system, with its effects often achieved through heterodimerization of nuclear receptors for vitamin A and vitamin D 1.
- Inflammation can lead to a decrease in serum retinol levels due to reduced absorption and increased urinary loss, potentially contributing to vitamin A deficiency 1.
Conversion and Measurement of Retinol
- The conversion of retinol to other units is crucial for understanding its levels in the body, with 1 RAE (Retinol Activity Equivalent) equal to 1 mg of retinol, 12 mg of β-carotene, or 3.33 IU (International Units) 1.
- The measurement of retinol in the blood is also important, with 1 mg/dL of retinol equivalent to 0.0357 mmol/L, and 1 mmol/L equivalent to 28 mg/dL 1.
Deficiency of Retinol
- Vitamin A deficiency, which can result from insufficient retinol, is a public health problem in many developing countries, particularly affecting children and pregnant women 1.
- Deficiency can lead to night blindness, impaired immune function, and increased susceptibility to infections, with severe cases resulting in keratomalacia and blindness 1.
- Certain conditions, such as liver disease, chronic alcohol consumption, and chronic kidney disease, can increase the risk of vitamin A deficiency, highlighting the need for monitoring and potential supplementation 1.
From the Research
Definition of Retinol
- Retinol, also known as all-trans retinol, is a precursor of retinoic acid and is widely used as a topical agent for the improvement of photodamage and acne vulgaris 2, 3.
- It is a form of vitamin A that is commonly used in skin care products to improve the appearance of fine wrinkles and skin texture 4.
Effects of Retinol on Skin
- Retinol has been shown to increase epidermal thickness, upregulate genes for collagen type 1 and collagen type 3, and increase procollagen I and procollagen III protein expression 3.
- It has also been found to improve fine wrinkles associated with natural aging by increasing glycosaminoglycan expression and collagen production 4.
- Retinol has been used in combination with other ingredients, such as salicylic acid, glycolic acid, and niacinamide, to treat mild acne and has been shown to be effective in reducing the number of acne lesions and improving skin appearance 5.
Comparison with Other Ingredients
- Retinol has been compared to retinoic acid, which is believed to provide even greater anti-aging effects, but has been found to be less irritating and more suitable for sensitive skin 3.
- It has also been compared to other topical treatments, such as azelaic acid, salicylic acid, and glycolic acid, and has been found to be effective in improving acne and skin appearance 6.