Can green tea reduce inflammation?

For thousands of years, people from many different cultures have enjoyed drinking tea. The hot beverage is believed to have many health benefits. Is fighting inflammation one of them? 

What is inflammation? 

Inflammation is a swelling that occurs when your immune systems responds to a tissue being injured – whether as a result of bacteria, trauma, toxins, heat, or any other cause. Damaged cells release chemicals that cause your blood vessels to leak fluid into the tissues, causing swelling that is designed to protect other tissues from the source of the damage. [1]

Inflammation doesn’t just begin when you see the swelling or feel the pain, but starts once the body fights off the infection or the foreign object. 

What causes inflammation? 

There are many causes of inflammation. The most common include the following: 

  • Pathogenic microorganisms like fungi, viruses and bacteria
  • Exposure to radiation or chemicals 
  • External injuries like a splinter in your finger 
  • Medical conditions and diseases that lead to inflammation end with the suffix ‘itis’. For example: 
    • Conjunctivitis: inflammation or infection of the thin, transparent membrane covering your eyeball and eyelid. Also known as ‘pink eye’. 
    • Bronchitis: inflammation of the bronchi of the lungs
    • Dermatitis: infection or inflammation of the skin 
    • Otitis media: also known as middle ear infection, an inflammation of the middle ear. 

What are the common signs of inflammation? 

Signs that you have acute inflammation include the following: 

  • Heat
  • Swelling 
  • Redness
  • Pain 
  • Loss of function 

When you experience loss of function, you struggle to move the inflamed body part. For example, you may find it difficult to walk up the stairs if you have inflamed joints.

Types of inflammation 

There are two types of inflammation: 

Acute inflammation 

This inflammation starts quickly and is your body’s response to irritants or infections. This can result in swelling, warmth, redness and pain around tissues and joints. This type of inflammation lasts a few days and the swelling and pain often go away in a few days or weeks. 

Chronic inflammation 

This inflammation lasts longer and does not go away. The body’s immune system continues to produce and send white blood cells to inflamed organs or tissues. These white blood cells may then attack other healthy cells and tissues. 

Factors that can potentially increase your risk of chronic inflammation are the following:

  • Diet high in saturated fats 
  • Diet high in refined sugar
  • Obesity 
  • Smoking 
  • Sleep problems
  • Stress
  • Being older 
  • Low sex hormones level 

The term ‘anti-inflammatory’ means a molecule or compound can reduce inflammation. Substances that can reduce inflammation may be artificial or natural. 

Can green tea reduce inflammation? 

There has been a long history of using green tea as medicine throughout history due to its healing properties. However, it is only recently that the benefits of green tea have been studied extensively.

This type of tea comes from the leaves of the plant Camellia sinensis. Green tea leaves contain catechins and other substances such as theaflavins, quercetin, theanine, gallic acid, chlorogenic acid and caffeine [2, 3]. 

The primary catechin found in green tea extracts is epigallocatechin-3-gallate (EGCG) [2]. As a significant polyphenol, EGCG has been shown in animal and laboratory studies and clinical trials to have anti-inflammatory and antioxidant properties [4, 5]. Due to its properties, it is believed that EGCG may have therapeutic effects on chronic inflammatory diseases such as arthritis, atherosclerosis and dry eye [6, 7]. 

Farmers hand-pluck the tea leaves, which they then immediately preserve using steam or heat after harvest.

A study [8] that examined the effectiveness of green tea extracts in reducing inflammation in eye cells called cornea epithelial cells showed that it could reduce inflammation and prevent cell damage to the cornea. Interleukin-1β is a cytokine, one of the cells secreted by the immune system, that mediates the inflammatory response [9].

Interleukin-1β is critical for the reaction of the human body against pathogens. However, it can exacerbate damage during chronic disease and lead to tissue injury [9]. Increased levels of interleukin-1β, a cytokine, can damage the eye’s cornea. In the study [8], EGCG inhibited multiple cytokines, including interleukin-1β.

This demonstrates that EGCG from green tea extracts may have beneficial effects against corneal inflammatory disease.

Green tea and rheumatoid arthritis 

In addition, EGCG is also shown to have beneficial effects against rheumatoid arthritis, another chronic inflammatory disease.

Rheumatoid arthritis (RA) is a common condition that is described as a chronic, autoimmune disorder that affects the synovial joints’ lining and is associated with socioeconomic burdens, progressive disability and premature death [10].

Patients with RA experience a limited range of motion, swelling and redness of the joints. There is currently no cure for RA, however, treatment strategies may include reducing inflammation to delay the progression of the disease. 

A study [11] discovered that catechins found in green tea extracts interfere with the interleukin-1β (IL-β) signalling pathway. In the body, IL-β signals the production of pro-inflammatory mediators and Cox-2 in cells called human rheumatoid arthritis synovial fibroblasts (FASFs).

So, it appears green tea may reduce the ability of IL-β to signal premature cells lining the synovial joints to produce cells that will lead to inflammation of the joints. Results [11] reinforce earlier findings that green tea extracts can potentially reduce inflammation of the joints in those with rheumatoid arthritis. 

Which green tea is best for inflammation? 

Not all green teas are made equal. 

A group of investigators [12] suggested that unfermented green tea yields the highest catechins level compared to fermented teas. When set side by side with black tea, green tea has a higher content of catechins.

Since black tea is fermented, catechins are oxidized to theaflavins, lowering the content of catechins in the process [12]. Since catechins have antioxidant properties, the higher the content of catechins, the greater the antioxidant and anti-inflammatory properties. Black teas have lower antioxidant and anti-inflammatory properties than green teas. 

Although green tea remains the best source of catechins, the antioxidant and anti-inflammatory properties may still be uneven. It is reported [13] that the origin and type of green tea will influence the level of catechins found in its leaves. How green tea is cultivated and the climate and temperature it grows also affect the level of catechins produced in the leaves [14]. 

Photograph: Deenida/Shutterstock

What are the popular types of green teas? 

Over the years, sencha is probably recognized as the most popular of all the green teas. Sencha is mainly cultivated and produced in Japan [15].

The quality of the leaf, also known as leaf grade and the place in Japan where it is grown will influence its taste. Sencha tea, once treated, can be transformed into Matcha, Bancha and Gyokuro tea species.

Matcha green tea leaf infusion has the highest amount of L-theanine and caffeine compared to Gyokuro and Bancha teas [16]. On the other hand, infusions of Bancha green tea have lower amounts of caffeine and L-theanine compared to Gyokuro tea infusions [16].

L-theanine is described as an amino acid involved in the formation of proteins used to produce insulin, adrenaline and neurotransmitters [17]. A scientific study [18] showed that L-theanine could modify the effects of caffeine, especially the stimulant activities of caffeine. The presence of L-theanine results in improved cognitive function, decreased blood pressure and improved mood and concentration. 

Gyokuro tea infusions may be more effective than Bancha green tea leaves in improving cognitive function.

How much green tea should I consume? 

After consuming green tea, the levels of EGCG in the blood drop for about two hours. Hence, it is recommended that you drink about 7-8 cups of green tea to enjoy the antioxidant and anti-inflammatory properties of green tea extracts.

The number of cups of green tea that you should consume will also depend on which type of tea you prefer. If you like Matcha tea, it is advised that you only drink 1-2 cups a day because it has the highest amount of L-theanine and caffeine compared to other teas.

Are there side effects to drinking green tea? 

Always inform your doctor if you feel any side effects from drinking green tea. Some reported side effects are related to its caffeine content. These can include irritability, tremors, anxiety and sleeping problems [19]. Choosing green tea with lower caffeine levels might help you avoid these common side effects. 

Liver problems are an uncommon side effect associated with green tea. While considered generally safe, there are few cases of liver damage after the intake of high concentrations of green tea extract [20]. 

Although green tea yields several potential benefits, such as anti-inflammatory and antioxidant properties, it is still advisable that you talk to your doctor before making dietary changes. This will help you take charge of your health while also enjoying the benefits of green tea. Making informed and shared decisions with your doctor will empower you to take positive actions regarding your health.  

[1] https://medlineplus.gov/ency/article/000821.htm
[2] https://pubmed.ncbi.nlm.nih.gov/25251944/
[3] https://www.sciencedirect.com/science/article/abs/pii/S0378874115301975?via%3Dihub
[4] https://pubmed.ncbi.nlm.nih.gov/19557821/
[5] https://pubmed.ncbi.nlm.nih.gov/15113942/
[6] https://pubmed.ncbi.nlm.nih.gov/17584048/
[7] https://iovs.arvojournals.org/article.aspx?articleid=2374874
[8] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3044696/#r29
[9] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3714593/
[10] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5920070/
[11] https://pubmed.ncbi.nlm.nih.gov/28532672/
[12] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7084675/
[13] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2998685/
[14] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7084675/
[15] https://www.sciencedirect.com/science/article/abs/pii/S0308814617316023?via%3Dihub
[16] https://doi.org/10.1016%2FS0924-2244(99)00044-8
[17] https://www.sciencedirect.com/science/article/abs/pii/S0924224499000448?via%3Dihub
[18] https://pubs.acs.org/doi/10.1021/jf030127i
[19] https://www.nccih.nih.gov/health/green-tea
[20] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3746392/

Photograph: Aleksey Mnogosmyslov/Shutterstock
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