Skin ageing is often characterised by the emergence of wrinkles. This natural process is primarily caused by the passage of time and exposure to the sun. Several active ingredients present in cosmetic treatments targeting skin ageing help to slow it down. What about green tea extract? Can this natural ingredient have an impact on the signs of ageing?
How are wrinkles formed?
Upon reaching a certain age, it is entirely normal and natural to have wrinkles. These form in various areas of the face, particularly on the forehead, around the eyes and around the lips. It's worth noting that we refer to wrinkles when the depth of the furrows exceeds 1 millimetre. If the furrows have a depth between 0.2 and 1 millimetre, they are considered as fine lines.
It is important to understand that the causes of skin ageing are multifactorial. Among these, we can mention the gradual decrease of collagen, elastin and hyaluronic acid in the dermis over the years. Collagen and elastin are support proteins of the skin's extracellular matrix that provide it with flexibility and firmness. Hyaluronic acid, on the other hand, is a macromolecule with a strong moisturising power and is capable of retaining up to 1000 times its weight in water.
The emergence of wrinkles is also promoted by certain external factors to the body, such as the pollution, the UV rays and the tobacco, elements that generate oxidative stress in the skin cells. This particularly damages the DNA, and the collagen and elastin fibres. It should be noted that UV rays alone are responsible for about 80% of premature skin ageing.
The effects of green tea on wrinkles?
The green tea (INCI: Camellia Sinensis Leaf Extract) is extracted from the leaves of Camellia sinensis, a shrub species belonging to the Theaceae family and native to the Far East. In addition to being a beverage appreciated for its flavour and digestive virtues, green tea is a natural ingredient abundantly present in the cosmetics market. Antioxidant, anti-inflammatory... its properties are numerous. Green tea is often incorporated into treatments targeting signs of ageing.
Green tea prevents the onset of fine dehydration lines.
Originating from a lack of hydration and a thinning of the hydrolipidic film, dehydration fine lines can be prevented by sufficient facial hydration. However, a study conducted on 24 volunteers showed that the daily application on the forearm of a moisturising cream containing 6% green tea extract for a month significantly increased the overall skin hydration and its suppleness. Thus, green tea extract would help to reduce dehydration fine lines.
Green tea protects the skin from oxidative stress.
The antioxidant properties of green tea extract are derived from its richness in polyphenols. These compounds act at several levels within the skin cells to prevent and inhibit damage caused by free radicals. They are notably capable of chelating, or binding to, certain metals involved in the generation of these reactive species (copper, iron...). In doing so, the polyphenols prevent them from producing free radicals. Studies have also shown that these compounds have a protective effect on certain antioxidant compounds such as vitamins C and E.
Finally, polyphenols can stimulate the production of certain endogenous antioxidant enzymes, such as superoxide dismutase (SOD) and glutathione peroxidase (GPx), both playing a crucial role in combating oxidative stress. Notably, SOD catalyses the dismutation of superoxide anions O2.- into oxygen O2 and hydrogen peroxide H2O2. GPx, on the other hand, ensures the transformation of organic hydroperoxides before they can damage cells.
Green tea prevents the degradation of collagen, elastin, and hyaluronic acid.
It has been demonstrated that green tea extract is capable ofinhibiting certain enzymes, playing a role in skin ageing. These include metalloproteinases, involved in the proteolytic degradation of extracellular matrix proteins, hyaluronidase, catalysing the hydrolysis of hyaluronic acids, and collagenase, responsible for breaking down the peptide bonds of collagen. By inhibiting these processes, green tea extract helps to delay skin ageing. However, the precise mechanisms through which it operates are still unknown to date.
KUKULA-KOCH W. & al. Applications of Tea ( Camellia sinensis) and its Active Constituents in Cosmetics. Molecules (2019).
TENCOMNAO T. & al. A Review of the Role of Green Tea ( Camellia sinensis) in Antiphotoaging, Stress Resistance, Neuroprotection, and Autophagy. Nutrients (2019).