Green tea extract is a decaffeinated mixture of polyphenols derived from the leaves of Camellia sinensis, a plant native to Asia. It contains antioxidants such as flavonoids, vitamins, and epigallocatechin-3-gallate (EGCG), which may help protect cells from damage. Green tea extract is believed to have antiviral, antioxidant, and potential cancer-preventing properties, and has been studied for its possible role in reducing the risk of cancers like prostate, stomach, and oesophageal cancer.

Is this used to correct a deficiency or achieve supramaximal levels?

Supramaximal

Is it taken for life span or health span?

Both

Is it targeting a specific disease? Or general health?

General health and neurodegenerative disease

Any genetic involvement?

Genes in cell cycle e.g CDK1 and DNA methylation genes like DNMT1

Is there a biomarker to track its effects?

Catechin levels in blood plasma or urine

MOA of supplement

Green tea extract offers several key benefits, primarily through its antioxidant and anti-inflammatory properties. It enhances natural enzymes like SOD and catalase that protect cells from damage and reduces inflammation by blocking pathways such as NF-κB and MAPK. It helps lower blood sugar by slowing carbohydrate breakdown and supports heart health by improving cholesterol levels and increasing nitric oxide to relax blood vessels. Additionally, it protects brain cells, potentially reducing harmful protein buildup associated with Alzheimer’s and Parkinson’s diseases.

Risk vs reward

+ May reduce all cause mortality

+ Reduces oxidative stress which contributes to cancer development

+ Lowers risk of neurodegenerative disease like dementia

+ May improve glucose metabolism

- Little to no effect on weight reduction

- Risk of developing iron deficiency with very high doses

- May have drug interactions like dabigatran and St Johns wart

Evidence for it?

This epidemiological study followed over 13,000 adults in Japan for 12 years to examine whether green tea consumption is linked to dementia risk. Results showed that higher green tea intake was independently associated with a lower risk of developing dementia, with each additional cup per day linked to a 4.8% risk reduction. However, consuming high amounts of both green tea and coffee together did not provide added protection and may reduce potential benefits, possibly due to excessive caffeine or differing effects of polyphenols in each beverage. These findings suggest moderate green tea consumption may support brain health, but excessive intake, especially with coffee, is not recommended.

This study reviewed 38 clinical trials to see how green tea affects inflammation and oxidative stress in the body. The results showed that green tea can improve markers of oxidative stress, such as antioxidant levels and enzymes that protect cells from damage. It also slightly reduced one inflammation marker (IL-1β). However, green tea did not significantly affect other major inflammation markers like CRP, IL-6, or TNF-α. Overall, green tea may help reduce oxidative stress, but there isn’t strong evidence that it lowers inflammation. More research is needed to understand its long-term effects on inflammation.

This case report describes a 48-year-old man with persistent iron deficiency anaemia, eventually linked to excessive green tea consumption—over 1.5 litres daily for two decades. Despite no signs of bleeding, gastrointestinal disease, or other common causes of anaemia, blood tests confirmed iron deficiency, likely caused by green tea's interference with iron absorption. While green tea contains powerful antioxidants like EGCG and is associated with reduced risks of stroke and diabetes, this case highlights that very high, long-term intake may lead to iron deficiency. These findings suggest that moderation is key, even with health-promoting beverages like green tea.

Evidence against it?

This study systematically reviewed clinical trials to assess whether green tea preparations aid in weight loss or weight maintenance. Across 15 weight loss studies and 3 weight maintenance studies involving nearly 2,000 participants, green tea preparations led to only small, statistically insignificant weight changes that were unlikely to be clinically meaningful. Similar results were found for other measures like BMI and waist circumference. While most side effects were mild and unrelated to the intervention, some adverse events required hospitalization. Overall, the evidence does not support a significant benefit of green tea preparations for weight management.

This case report describes a 48-year-old man with persistent iron deficiency anaemia, eventually linked to excessive green tea consumption—over 1.5 litres daily for two decades. Despite no signs of bleeding, gastrointestinal disease, or other common causes of anaemia, blood tests confirmed iron deficiency, likely caused by green tea's interference with iron absorption. While green tea contains powerful antioxidants like EGCG and is associated with reduced risks of stroke and diabetes, this case highlights that very high, long-term intake may lead to iron deficiency. These findings suggest that moderation is key, even with health-promoting beverages like green tea.

Best bioavailable form?

Tea, capsule or powder

Advice on taking it?

With food to reduce GI effects

Green Tea Extract