In a recent review article published in the journal  Antioxidants , scientists from the United States and South Korea examine the benefits of topical and dietary supplementation with blueberries to prevent skin damage mediated by environmental stressors and preserve skin health.

Background

It is known that environmental stressors, including air pollutants, ozone (O ₃ ) and ultraviolet (UV) radiation damage the skin and induce premature aging. Excessive exposure to these stressors can lead to chronic production of reactive oxygen species (ROS), which can suppress the skin defense system, in addition to inducing oxidative stress and premature aging.

Human skin physiology

Human skin is made up of three main layers, including the epidermis, dermis, and hypodermis. The epidermis is the outermost layer of the skin and acts as the first line of defense against environmental stressors, microorganisms, and physical trauma.

The dermis, which lies directly beneath the epidermis, contains blood vessels, lymphatic vessels, nerves, and various immune cells, including fibroblasts. The hypodermis, also known as the subcutaneous layer, is a thick layer of adipose tissue that has many important functions, including water storage, absorption of lipophilic compounds, and protection.

The skin defense system consists of several enzymatic and non-enzymatic antioxidants that act synergistically to eliminate ROS, prevent lipid peroxidation, and suppress inflammation.

Catalase, superoxide dismutase, and glutathione peroxidase are the major enzymatic antioxidants that are present in higher concentrations in the epidermis than in the dermis. Non-enzymatic antioxidants mainly include vitamin C, vitamin E, glutathione, uric acid and ubiquinol, all of which are also present in higher concentrations in the epidermis than in the dermis.

Environmental stressors

A certain level of skin exposure to UV light is essential for producing vitamin D. However, prolonged exposure to UV light can lead to serious skin complications, including skin cancer.

Pollutants emitted by power plants, chemical plants, and automobiles are important sources of O ₃ . Daily exposure to elevated levels of O ₃ It can cause cardiorespiratory complications and skin adversities.

Suspended particulate matter (PM) is the leading air pollutant produced by industrial waste, burning fossil fuels, volcanoes, dust storms and forest fires. Ultrafine PM is known to cause skin barrier dysfunction and atopic dermatitis.

The main mechanisms involved in skin damage mediated by environmental stressors include chronic ROS production, suppression of cellular antioxidants, induction of oxidative stress, and DNA damage.

Bioactive compounds in blueberry

Blueberries are a rich source of many bioactive compounds with antioxidant, anti-inflammatory, immunomodulatory, and antimicrobial properties, including flavonoids and other polyphenolic compounds.

Anthocyanin is the main polyphenol in blueberries, responsible for its blue color. This compound has strong antioxidant, anti-inflammatory and antibacterial properties.

Other polyphenolic compounds in blueberries include flavonols, ellagitannins, proanthocyanidins, hydroxycinnamic acids, gallotannins, and hydroxybenzoic acids. When consuming blueberries, these compounds undergo important modifications during metabolism, leading to the generation of several polyphenolic metabolites that can be detected in the blood.

Catabolism of cranberry-derived metabolites by the gut microbiota may provide protection against several health complications, including gastrointestinal problems, diabetes, cardiovascular and neurodegenerative diseases, as well as cancers.

In addition to polyphenols, blueberries are a rich source of vitamins A, C and E, which have well-established beneficial effects on the skin.

Cranberry topical application

Studies investigating the topical application of phytochemicals have indicated that bioactive compounds present in blueberries, such as vitamin C, vitamin E, and resveratrol, provide protection against common environmental stressors.

According to the available literature, direct topical application of phytonutrients and extracts derived from bilberry reduces O-induced skin inflammation. ₃ and UV radiation. O-induced keratinocyte proliferation and migration ₃ It can also be prevented by pretreatment with cranberry extract.

Treatment of human dermal fibroblasts with cranberry anthocyanin has been found to reduce nuclear factor kappa B (NFkB) activation and prevent collagen degradation. Bilberry extracts also appear to protect the epidermis from O-mediated damage. ₃ and UV radiation by inhibiting inflammation and oxidative stress.

Mechanistically, cranberry extracts have been shown to modulate NFkB and nuclear factor erythroid 2-related factor 2 (Nrf2) pathways to reduce UV radiation-induced inflammation and increase antioxidant defense, respectively.

Another health benefit of topical application of cranberry extract is the improvement of skin barrier function. UV radiation-mediated degradation of the skin proteins filaggrin and involucrin is responsible for the loss of barrier function and the induction of chronic skin inflammation. Topical application of blueberries has been found to increase the levels of these proteins to protect against UV radiation.

Topical application of cranberry extract to the skin of diabetic patients appears to improve the softness and hydration of the skin, in addition to preventing the formation of skin wrinkles.

Blueberry Dietary Supplementation    

Studies directly investigating the effect of dietary supplementation with blueberries on skin health are scarce. This could be due to the low bioavailability of bioactive compounds in the blood after ingestion of blueberries. However, there is evidence to suggest that dietary supplementation with blueberries may improve skin vascular functions.

A study conducted in UVB-irradiated hairless mice has indicated that dietary supplementation with fermented black rice and blueberries with  Lactobacillus plantarum Improves skin hydration and barrier function.

Dietary supplementation with bioactive blueberry compounds also appears to reduce skin roughness and increase elasticity. Furthermore, oral supplementation with cranberry-derived epigallocatechin-3-gallate (EGCG) prevents UV radiation-mediated loss of epidermal barrier function in hairless rats.

An imbalance in the skin and gut microbiota is associated with a variety of skin complications, such as atopic dermatitis, psoriasis, acne vulgaris, dandruff, and skin cancer. The compositions of the skin and gut microbiota are maintained by bidirectional mechanisms.

Dietary supplementation with blueberries appears to increase certain gut microbial species, which could have beneficial effects in patients with psoriasis. Dietary supplementation with blueberries has also been found to increase levels of beneficial metabolites derived from the gut microbiota, including short-chain fatty acids and butyrate, which may improve skin health by reducing oxidative stress and inflammation.