Green Tea and Prostate Cancer: Prevention, Treatment, EGCG & Safety

What Is Green Tea?

Green tea is made from the leaves of Camellia sinensis, the same plant used to make black and oolong tea.

The difference is mainly how the leaves are processed.

Green tea leaves are heated soon after harvesting, which limits oxidation and helps preserve naturally occurring compounds called catechins.

The major catechins include:

• EGCG — epigallocatechin-3-gallate;
• EGC — epigallocatechin;
• ECG — epicatechin gallate; and
• EC — epicatechin.

EGCG is the compound most frequently studied in prostate-cancer research.

Why Are Green Tea Catechins Studied in Prostate Cancer?

Laboratory studies suggest that EGCG and related catechins can influence several biological pathways relevant to prostate-cancer cells.

Experimental effects have included:

• reduced prostate-cancer cell proliferation;
• changes in androgen-receptor signaling;
• changes in PSA production by cultured cancer cells;
• promotion of programmed cell death;
• effects on gene regulation and methylation; and
• reduced tumor development in some animal models.

These findings explain why green tea continues to be studied.

Does Green Tea Prevent Prostate Cancer?

At this point, we cannot say for sure.

Green tea has attracted considerable interest because it contains natural compounds, particularly catechins such as EGCG, that have shown potentially beneficial effects in laboratory research. When we look at studies involving people, however, the picture is much less clear.

According to the National Cancer Institute (NCI), some observational studies—particularly studies conducted in Asian populations—have found an association between higher green-tea consumption and a lower risk of prostate cancer. Other studies, including prospective cohort studies that follow people over time, have not consistently found the same protective effect.

Some observational research has even reported an association between green-tea consumption and a higher risk of advanced prostate cancer. Findings like these need to be interpreted carefully. Observational studies can identify associations, but they cannot by themselves prove that green tea either increases or decreases prostate-cancer risk.

There are many reasons why studies may reach different conclusions. These include differences in:

• overall diet;
• smoking and alcohol use;
• genetics and ancestry;
• the type and preparation of tea;
• the amount and frequency of tea consumed;
• other lifestyle habits; and
• how each study was designed and conducted.

For patients, the practical message is fairly simple: green tea can certainly be enjoyed as part of a balanced diet, but current evidence is not strong or consistent enough to recommend it as a proven way to prevent prostate cancer.

See our broader prostate cancer prevention guide.

What Do Clinical Trials Show?

Green-tea catechins have been studied in several clinical settings, including men with high-grade prostatic intraepithelial neoplasia (HGPIN), men with prostate cancer who were preparing for surgery, and other groups considered at increased risk of prostate cancer.

So far, the results have been interesting but not consistent enough to establish green tea or green-tea extracts as a prostate-cancer treatment or prevention strategy.

Men With HGPIN or Other Suspicious Prostate Findings

Some of the most discussed studies have involved men with HGPIN or atypical small acinar proliferation (ASAP), findings that may lead to closer prostate monitoring.

In some randomized trials, men taking standardized green-tea catechins showed reductions in PSA or differences in certain biopsy findings. These results have generated interest, but they need to be interpreted carefully.

For example, a randomized placebo-controlled trial of a standardized green-tea catechin preparation found a reduction in PSA and a difference in a secondary combined biopsy outcome in a subgroup of men. However, the study did not show a statistically significant reduction in the overall number of prostate-cancer diagnoses compared with placebo.

Another randomized trial in men with HGPIN also reported a reduction in PSA, but again did not demonstrate a statistically significant reduction in prostate-cancer incidence.

It is also important to understand that HGPIN is not the same as prostate cancer, and it should not be viewed as an inevitable step that will eventually become cancer. This is one reason changes in HGPIN, ASAP, or PSA alone cannot tell us whether a supplement ultimately prevents prostate cancer.

Green Tea Before Prostate Surgery

Researchers have also studied green tea and standardized catechin extracts for a few weeks before radical prostatectomy. These studies allow researchers to examine blood and prostate tissue after exposure to green-tea compounds.

Some studies have reported small changes in PSA or other biological markers related to cancer growth, inflammation, oxidative stress, or growth-factor pathways. Other studies have found little or no significant difference in important tumor-tissue markers.

These findings can help researchers understand what green-tea compounds may be doing biologically, but they do not by themselves show that green tea is treating the cancer.

Most of these pre-surgery studies were relatively small and short. They were not designed to determine whether green tea leads to:

• fewer prostate-cancer recurrences;
• a lower risk of metastasis;
• longer prostate-cancer-specific survival; or
• longer overall survival.

This distinction is important: a change in PSA, IGF-related markers, VEGF, or another laboratory biomarker can be scientifically interesting, but it is not the same as showing that a treatment slows prostate cancer, prevents metastasis, or helps patients live longer.

For now, I would describe the clinical research on green-tea catechins as promising enough to continue studying, but not sufficient to consider them an established prostate-cancer therapy.

Can Green Tea Treat Advanced Prostate Cancer?

Based on the clinical evidence available so far, green tea or green-tea extracts have not shown meaningful activity as a treatment for advanced prostate cancer.

Small clinical studies have looked at concentrated green-tea preparations in men with advanced prostate cancer, including men whose cancer was no longer responding adequately to hormone therapy.

In one study involving 19 men, none achieved the PSA response defined by the researchers, and the disease continued to progress during follow-up. In another study involving 42 men, only one patient had a PSA reduction of at least 50%, and that response lasted for less than two months.

These were small studies, so they cannot answer every question about green tea and prostate cancer. However, the results do not provide evidence that green-tea extract can control established advanced prostate cancer in a clinically meaningful way.

For patients, the important point is that green tea should not be viewed as a replacement for established prostate-cancer care. Modern treatment is selected according to the stage and biology of the cancer and may include active surveillance for appropriate localized disease, surgery, radiation therapy, androgen-deprivation therapy (ADT), newer hormonal therapies, chemotherapy, radioligand therapies such as PSMA-targeted treatment, or treatments chosen according to specific tumor biomarkers.

Drinking green tea as part of a balanced diet is a different matter. But if you are considering a concentrated green-tea or EGCG supplement during prostate-cancer treatment, I recommend discussing the exact product and dose with your oncology team, particularly because supplements can have side effects or interact with medications.

Does Green Tea Lower PSA?

Some small clinical studies have reported modest reductions in PSA after the use of green tea or standardized green-tea catechins. Other studies, however, have found little or no meaningful change.

This is important because a lower PSA does not automatically mean that prostate cancer has been eliminated or brought under control. PSA is a useful marker, but it is only one part of the overall clinical picture.

When I interpret a PSA result, I look at it alongside factors such as:

• the underlying diagnosis;
• the prostate cancer Grade Group;
• the stage of the disease;
• MRI or PSMA imaging when clinically appropriate;
• biopsy findings; and
• previous and current treatment.

A small change in PSA after taking green tea or a supplement should therefore not be interpreted on its own as evidence that the cancer is shrinking or that the risk of progression or metastasis has decreased.

If you would like to understand what your PSA result actually means, including how PSA is interpreted before and after prostate-cancer treatment, see our detailed PSA test guide.

How Much Green Tea Should You Drink for Prostate Cancer?

There is no established prostate-cancer prevention or treatment dose.

Studies have used widely different exposures, including:

• several cups of brewed tea per day;
• standardized catechin preparations;
• hundreds of milligrams of EGCG; and
• very high-dose extracts.

This means it is not medically appropriate to prescribe “3–5 cups” or a specific EGCG dose as proven prostate-cancer treatment.

If you enjoy green tea, moderate beverage intake can fit within a healthy diet unless caffeine or another medical issue makes it unsuitable.

Brewed Green Tea Is Not the Same as Green Tea Extract

Can Green Tea Extract Damage the Liver?

Yes, although this appears to be uncommon.

Green tea as a beverage is generally considered very different from concentrated green-tea extracts sold in capsules or tablets. According to the NCCIH and the NIH Office of Dietary Supplements, cases of liver injury have been reported mainly with these higher-dose extract products.

Most people who use green tea products do not develop liver problems, but some reported cases have been serious, and rare cases of liver failure have occurred.

The risk may depend on the type and concentration of the extract, the dose, and how the product is taken. Some evidence suggests that taking concentrated green-tea extracts on an empty stomach may increase exposure to catechins and could raise the risk of liver-related side effects.

It is sensible to stop the supplement and seek medical advice if symptoms suggesting liver injury develop, such as:

• pain or discomfort in the upper abdomen;
• unusual or persistent fatigue;
• loss of appetite;
• dark urine;
• pale or unusually light-colored stools; or
• yellowing of the skin or the whites of the eyes (jaundice).

If you have existing liver disease, take prescription medicines, or are receiving prostate-cancer treatment, it is particularly important to discuss a concentrated green-tea or EGCG supplement with your doctor or pharmacist before using it.

What Side Effects Can Caffeine Cause?

Green tea naturally contains caffeine unless it has been specifically decaffeinated. Many people tolerate this amount without difficulty, but some are more sensitive to caffeine than others.

Possible caffeine-related effects can include:

• difficulty sleeping or lighter sleep;
• nervousness or feeling unusually restless;
• jitteriness or mild tremor;
• palpitations or a faster heartbeat;
• headache;
• stomach discomfort;
• increased urinary frequency; and
• a temporary rise in blood pressure.

For men who already have urinary frequency, urgency, or nocturia related to benign prostatic hyperplasia (BPH), caffeine may sometimes make bladder symptoms more noticeable.

If you find that green tea seems to worsen urination, sleep, palpitations, or other symptoms, reducing the amount you drink or choosing a decaffeinated version may be reasonable.

Does Decaffeinated Green Tea Work Better for Prostate Cancer?

There is no good evidence that decaffeinated green tea is more effective against prostate cancer than regular green tea.

The main advantage of choosing a decaffeinated product is usually better tolerability rather than a stronger anticancer effect. This may be helpful for people who are sensitive to caffeine or who notice symptoms such as:

• palpitations;
• difficulty sleeping;
• urinary urgency;
• increased urinary frequency; or
• nervousness or anxiety related to caffeine.

Some clinical studies investigating green-tea catechins have used standardized decaffeinated preparations. This allows researchers to study compounds such as EGCG while reducing caffeine-related side effects.

However, removing caffeine does not turn green tea or a catechin extract into a proven prostate-cancer treatment. Decaffeinated green-tea preparations should still be viewed as an area of research rather than an alternative to established prostate-cancer care.

If you are considering a concentrated green-tea or EGCG supplement, particularly during prostate-cancer treatment, it is sensible to discuss the specific product and dose with your doctor or pharmacist.

Does Brewing Time Matter?

Brewing method affects how many catechins and how much caffeine enter the drink.

Longer steeping generally extracts more compounds.

But the exact content varies widely according to:

• tea variety;
• leaf amount;
• water temperature;
• steeping time;
• processing; and
• brand.

There is no validated brewing method that turns green tea into a prostate-cancer medicine.

What About Bottled or Iced Green Tea?

Bottled and ready-to-drink green teas can be very different from freshly brewed tea. The amount of actual tea, catechins, caffeine, and added sugar can vary considerably from one product to another.

Some bottled products contain only modest amounts of green-tea extract but relatively large amounts of added sugar. For general health, plain brewed green tea or an unsweetened bottled version is usually a better choice than a sugar-sweetened tea drink.

It is also worth checking the nutrition and ingredient label rather than assuming that a product contains a meaningful amount of catechins simply because the words “green tea” appear on the front of the bottle.

If you are choosing green tea for its potential health benefits, look for products with little or no added sugar and remember that the catechin content of commercial drinks is not standardized.

Does Green Tea Prevent Other Cancers?

Green tea has been studied in relation to several types of cancer, which is one reason it is often described as having potential anticancer properties. However, the evidence in people is much less certain than this reputation may suggest.

According to the National Center for Complementary and Integrative Health (NCCIH), studies looking at green tea and cancer prevention have produced inconsistent results. Some observational studies have suggested possible associations with lower cancer risk, while others have found little or no clear benefit.

These differences can reflect many factors, including the type of cancer studied, the amount and form of green tea consumed, overall diet, lifestyle, genetics, and differences in study design.

For that reason, green tea should not be presented as a proven way to prevent cancer in general. It can certainly be enjoyed as part of a healthy diet, but it should not replace established cancer-prevention measures such as avoiding tobacco, maintaining a healthy weight, staying physically active, limiting alcohol, and following recommended screening programs.

Does Green Tea Treat Diabetes?

Green tea should not be considered a treatment for diabetes.

Some studies have looked at whether green tea or its catechins may influence blood glucose, insulin sensitivity, or HbA1c. The results have been mixed, and any benefits reported have generally been small and not consistent enough to support green tea as a glucose-lowering therapy.

For people with type 1 diabetes, green tea cannot replace insulin. Insulin is essential because the body is unable to produce enough of it on its own.

For people with type 2 diabetes, drinking unsweetened green tea can certainly fit into a healthy eating pattern, but it should not replace prescribed medication, nutrition therapy, physical activity, or other parts of an established diabetes-management plan.

Claims that green tea can produce a substantial reduction in HbA1c, particularly in type 1 diabetes, go beyond what current clinical evidence supports.

If you have diabetes and are considering concentrated green-tea or EGCG supplements, it is sensible to discuss them with your doctor or pharmacist, especially if you take glucose-lowering medication or have other medical conditions.

Does Green Tea Lower Cholesterol?

Green tea may have a small effect on cholesterol levels, but it should not be viewed as a cholesterol-lowering treatment on its own.

According to the National Center for Complementary and Integrative Health (NCCIH), studies suggest that green-tea products may modestly reduce total cholesterol and LDL cholesterol, often referred to as “bad” cholesterol.

The effect appears to be relatively small, and research has not shown a consistent or meaningful increase in HDL cholesterol, the type commonly referred to as “good” cholesterol.

For someone with elevated cholesterol, drinking unsweetened green tea can be part of an overall heart-healthy eating pattern. However, it should not replace treatments with well-established cardiovascular benefits, such as statins or other lipid-lowering medicines, when these have been recommended based on a person’s cholesterol levels and overall cardiovascular risk.

If you are already taking cholesterol medication and are considering a concentrated green-tea or EGCG supplement, it is reasonable to discuss the product with your doctor or pharmacist because supplements can have side effects and may interact with medications.

Does Green Tea Help With Weight Loss?

Green-tea catechins and caffeine may have a small effect on body weight.

That effect is generally not large enough to treat obesity.

Concentrated “fat-burning” green-tea extracts can expose patients to much larger EGCG doses and are among the products that have been associated with liver injury.

Does Green Tea Treat Hepatitis, Arthritis or Skin Disease?

The broad therapeutic claims in the legacy article should not remain.

Green tea should not be recommended as treatment for:

• viral hepatitis;
• arthritis;
• diabetes;
• skin diseases; or
• other major illnesses

unless there is specific evidence and clinical guidance for the condition in question.

This page should remain focused on prostate cancer.

Does Green Tea Increase Blood Clotting?

The old article states that green tea increases blood coagulation because it contains vitamin K.

That is not a useful general description of normal green-tea consumption.

The more important issue is that green tea and concentrated green-tea products can interact with medicines.

Patients taking drugs with a narrow therapeutic range—including anticoagulants—should tell their clinician or pharmacist about regular herbal/supplement use.

NCCIH also reports interactions between high-dose green tea or extracts and medicines such as:

• nadolol;
• atorvastatin; and
• raloxifene.

Green Tea During Prostate Cancer Treatment

Normal beverage intake is different from taking a concentrated extract.

A man receiving prostate-cancer treatment should tell his oncology team if he is taking:

• EGCG capsules;
• high-dose green-tea extract;
• multi-ingredient antioxidant formulas; or
• “prostate cancer” supplements containing green-tea catechins.

This is particularly important during:

• chemotherapy;
• radiation;
• targeted therapy;
• other systemic cancer treatment; and
• treatment involving multiple prescription medicines.

A Concerning Combination-Supplement Study

NCI describes a randomized study in men with HGPIN or atypical small acinar proliferation that tested a combination supplement containing:

• lycopene;
• selenium; and
• green-tea catechins.

The men receiving the supplement had a higher incidence of prostate cancer on repeat biopsy than men receiving placebo.

That trial does not prove green tea itself caused the increase, because several ingredients were combined.

But it demonstrates an important principle:

Green Tea vs Lycopene: Same Lesson

Green tea and lycopene have both shown interesting effects in laboratory prostate-cancer research.

Both are also components of healthy foods or beverages.

But neither has enough human evidence to be prescribed as prostate-cancer prevention or treatment.

The most defensible approach is to focus on a healthy overall eating pattern rather than trying to identify one “anticancer” food.

What Should a Man With Prostate Cancer Do?

1. Drink green tea if you enjoy it and tolerate caffeine.
2. Choose unsweetened tea rather than high-sugar bottled products.
3. Use decaffeinated tea if caffeine worsens urinary symptoms, sleep or palpitations.
4. Do not expect a specific number of cups to prevent or cure prostate cancer.
5. Do not replace active surveillance or established treatment with green tea.
6. Be much more cautious with concentrated green-tea/EGCG extracts than with the beverage.
7. Tell your clinician about high-dose extracts and supplement combinations.
8. Stop an extract and seek medical advice if possible liver-injury symptoms develop.

Questions to Ask Before Taking EGCG or Green-Tea Extract

1. Why am I taking this—general nutrition, cancer prevention or cancer treatment?
2. How much EGCG does the product contain?
3. Does it contain caffeine?
4. Am I taking it on an empty stomach?
5. Do I have liver disease?
6. Could it interact with my medicines?
7. Does it contain other antioxidants or herbs?
8. Am I using it instead of a proven prostate-cancer treatment?

Medical information notice: Green tea is a beverage, not an established prostate-cancer therapy. Concentrated extracts can have pharmacologic effects and should be discussed with a clinician when cancer treatment, liver disease or interacting medicines are involved.