Green Tea and its Many Health Benefits
By Evelin Maza
Skin cancer is currently one of the most frequent and increasing health-related problems around the world. Every year more and more cases are diagnosed. And the main reason is quite clear: overexposure to ultraviolet radiation (UVR) (1).
While impressive advances have been made in treatment, scientists have recently been focused on developing new and improved ways to prevent skin cancer all together. This is because the current methods of prevention are not very reliable or effective. These include: avoiding exposure to the sun during peak hours of UVR, wearing protective clothing, and the use of sunscreen.
Sunscreen is another controversial issue, because there are many details to touch on. For one, it relies heavily on the proper use by the patient (2). Also, sunscreens have no effect on the damage caused by previous UVR exposure.
So, the study of other possible means of protection against the harmful effects of UV radiation is essential! This includes studying the qualities of green tea.
Green tea: an overview
Green tea comes from the plant Camellia sinensis, and it contains large amount of polyphenols, which are the elements responsible for its protective qualities.
The four main polyphenols: epicatechin (EC), epicatechin-3-gallate (ECG), epigallocatechin (EGC), and epigallocatechin-3-gallate (EGCG) (3). EGCG has proven to produce the most powerful effects!
Studies have shown that consuming tea lowers the risk of certain cancers, including stomach, bladder, and liver cancer. It has even slowed down the growth of tumors in studies in mice.
Another study in mice proved that by applying green tea extracts topically to the skin, tumor growth and development was reduced.
But slowing down tumors isn’t the only beneficial effect polyphenols has on human skin. By treating the skin with EGCG, scientists managed to lower the amount of visible photoaging and immunosuppression (4).
By photoaging, we mean that less wrinkles developed on the skin due to exposure to UV radiation and the destruction of collagen that it can cause. Immunosuppression refers to the fact that normally UVR lowers the skin’s natural defenses against certain irritating substances, much like an allergic reaction.
Photoprotective effects: How and Why?
The main goal of the scientists involved in these studies has been to pinpoint exactly how the components of green tea produce these effects. Which processes and chemicals are involved?
Inside the cells, EGCG is capable of lowering the amount of sunburn cells in the skin after its exposure to UVR. Sunburn cells are skin cells undergoing apoptosis, or cell death. So, EGCG limits the number of cells that die off! It achieves this by increasing the level of proteins which prevent cell death, and lowering the amount of proteins which stimulate it. Easy enough, right?
Green tea also stops the movement of specialized cells like, neutrophils and macrophages, towards the area of skin exposed to radiation. These cells are involved in inflammatory reactions. And, in turn, this inflammation leads to skin damage, the suppression of the immune system, and even the development of cancer (5).
These specialized cells are also a great source of free radicals. Meaning that by halting these cells, the components of green tea also halt oxidative stress.
In a biochemical aspect, it has been proven that radiation from the sun suppresses the immune system by messing with the production of certain molecules, such as cytokines. Some studies have shown that EGCG prevents these changes.
It all depends on the interleukin (IL), proteins that regulate the immune system. The EGCG in green tea slows down the activity of IL-10, which prevents allergic reactions and hypersensitivity, while it boosts IL-12, which stimulates immune responses.
Tumors achieve their great size and speedy growth by constantly creating blood vessels and, surprisingly, EGCG can even slow down tumor growth by preventing the formation of these new vessels (6)!
On a molecular level, it is well known that UVR depletes the body’s natural antioxidants and leads to oxidative stress. EGCG neutralizes these free radicals directly with its own spare electrons. But, also, it avoids damage indirectly by making DNA strands more stable.
UVR also produces health complications by altering the way that damaged DNA leads cells to wither and die. Radiation allows the DNA to continue to reproduce, leading to abnormal growth, aka tumors. But EGCG stops this continuation of deformed growth.
After seeing all of the positive effects that the polyphenols found in green tea can offer, it’s no wonder scientists have developed such an interest.
The combination of the physical barrier created by regular sunscreen and all the biological processes stimulated by EGCG is definitely the future of skin protection and skin cancer prevention!