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Tea and Cancer Prevention: Strengths and Limits of the Evidence

Charles M. Carlsen

Published April 25, 2024
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What gives you the needed boost to start your day stress-free in the morning? What beverage do you take right after breakfast to relieve body fatigue? You got it right – Tea. Tea remains among the most consumed drinks on earth. This implies that it comes second to water which is believed to be consumed more than anything else in the universe.
Scientists and researchers have become highly interested in tea as its consumption rates have soared globally. The source of tea is Camellia Sinensis leaves. Though all teas come from these leaves, they are not processed resulting in the same thing.
The scientific community has told the tale of tea's potential benefits on health, especially in cancer preventive activities.

Study about Tea's Cancer-Fighting Potential

We had noted before that all teas might come from the same leaves but differ in processing; some are processed more than others. Let's talk about the White tea for a moment. The white tea, during its making, is steamed quickly and then dried. Its leaves are said to be "fresh." Green tea, on the other hand, is steamed or fired before being rolled. The black and Oolong teas somehow have an opaque colour. They get this dark colour from additional processing of the dried fermented leaves.
Some researchers are of the opinion that processing may play a part in tea’s cancer-fighting potential. The key is a group/class of chemicals called polyphenols.
Chemical analysis supported their theory. It is said that white tea has the same types of polyphenols that can be seen in green tea; however, they are not in the same proportions. White tea is known to have a more significant amount, which may be responsible for its enhanced cancer-battling potential. Those present in more significant amounts may be responsible for white tea's enhanced cancer-fighting potential.
Dark tea, on the other hand, holds promise in the fight against cancer. Its bioactive compounds, like catechins and alkaloids, are key players. These elements may help tackle inflammation—a cancer growth factor—by impacting specific body pathways. 
For instance, studies have shown that Pu'er tea can hinder inflammatory responses by affecting protein levels within specific cell signalling routes. But there's more to understand about how dark teas work their magic against cancer cells. The quality of evidence varies; hence, we need to do deeper research on its actual impact before recommending it as a reliable adjuvant for prevention or therapy.
So while early signs are hopeful, what you should keep in mind right now is, they're just hints at what could be a larger truth yet uncovered.

The Power of Antioxidants in Tea

The polyphenols in tea are popularly known to be strong antioxidants. Prevention of modulation of carcinogen metabolism, DNA mutation/damage, and oxidative stress have been recommended as possible mechanisms for preventing cancer for tea and tea polyphenols.
The antioxidants in tea work by tackling harmful molecules in your body. These bad players can hurt your cells and up the chances of heart trouble. Studies show that both green and black teas drop low-density lipoprotein—think of it as the "bad" cholesterol, a key player in clogging arteries.
Though this doesn't directly link to dodging heart attacks or strokes yet, keeping those levels down is seen as a step toward better cardiovascular health. 
Reactive Oxygen Species come into play…
Reactive oxygen species (ROS) play a dual role in cancer cells, which includes both promoting and inhibiting carcinogenesis. Tea comes into play with its anti- or pro-oxidative properties. The active compounds in this beverage, tea polyphenols, can directly or indirectly salvage ROS to reduce cancer metastasis and oncogenesis. Interestingly, the excessive levels of ROS incited by drinking tea could influence programmed cell death (PCD) or non-PCD of cancer cells.

Varieties of Tea and Their Benefits

A lot of brews these days are generically called tea; however, purists only see green tea, white tea, black tea, Oolong tea, and pu-erh tea as the real deal. All these teas contain unique antioxidants known as flavonoids. The most dominant is the ECGC. This ECGC helps fight against free radicals responsible for clogged arteries, cancer cell growth and heart disease.
All these teas mentioned above also have theanine and caffeine, which affect the brain and seem to heighten mental alertness. This, as you should know, is responsible for your early morning agility when you wake up from bed and take a cup of tea.
The polyphenol content (Flavonoids) in the tea leaves is reduced once the processing begins. The further the stage of processing, the further it reduces. Black teas and Oolong teas are oxidized or fermented, so they have lower concentrations of polyphenols than green tea, but their antioxidant power is still high.
Some of the benefits of these varieties include :
1. Green tea: Leaves for this type of tea are steamed during its manufacture hence it has a higher EGCG count than others. This may affect growth of lung, breast, bladder, stomach, pancreatic and colorectal cancers through the antioxidizing ability of green tea.
  • It helps prevents arteries from getting blocked, 
  • It helps to burn fat and prevent oxidative stress on the brain, 
  • It reduces the risk of neurological disorders like Parkinson's and Alzheimer’s, and other diseases, 
  • It reduces the risk of stroke, and improves cholesterol levels.
2. Black tea: A research found out that black tea has the highest amount of caffeine per gram and therefore it is used to kick off flavored teas like chai and some instant teas too.
  • Itprotects the lung from harmful chemicals during cigarette smoking.
  • It may also reduce the risk of stroke.
3. White tea: The leaves are not cured or fermented. In a recent study, white tea was found to have the most potent anti-cancer activities when compared with other types of teas.
4. Oolong tea: After feeding animals antioxidants from oolong tea during an experiment, those fed had lower bad cholesterol levels. Another type of Oolong Tea known as Wuji claims to be a weight loss supplement; however, recent studies do not back this notion up.
5. Pu-erh tea: This category of tea is made using aged and fermented leaves which are similar to those used in making black tea but unlike it, they are pressed into cakes. An experiment showed that pu-erh fed animals gained less fat than their counterparts and had reduced low density lipoproteins (LDL).

Understanding the Science Behind Tea Polyphenols

Tea polyphenols, particularly EGCG found in green tea, have shown promise in preventing cancer. They've been tested for efficacy against a range of cancers, including those affecting the skin, lungs, prostate, and breasts. While animal studies suggest potential benefits, translating these results to human prevention is complex since high lab-concentrated doses differ from what people can consume.
These compounds may work by diverse biological mechanisms, which are still under intense study. However, how they function inside humans remains unclear due to variations in bioavailability when ingested through diet or supplements. 

Evaluating the Research on Tea and Cancer

Scientific minds have recently explored tea's impact on health, with a focus on whether it can fend off cancer. Tea packs flavonoids—these may lower inflammation and keep blood sugar even. Experts believe that these elements could help prevent some cancers but admit proof is still thin.
They say drinking more tea might be good for you if your meals lack fruits or grains full of these helpful compounds. 

Strengths of Current Epidemiological Evidence

Now, let's dig into the strengths of our current evidence on tea and cancer. Large-scale studies give us solid data showing how people who drink tea might have different rates of certain cancers compared to those who don't. Top health bodies like NCI - think big-league science labs working hard day in and day out - offer this robust research for you to trust.
You can hit up their website or drop a call to get the low-down straight from them – all thanks to thorough work by experts in cancer prevention and epidemiology providing reliable info with real-world relevance. 

Limitations in Existing Study Designs

Current studies on tea and cancer prevention often show limits. Many don't have a large enough group of people to give strong results. They also may last too short a time to see long-term effects.
Others use self-reported data, which can be less accurate than medical records or direct measures. Plus, they might not account for other lifestyle factors that could impact the outcome like diet or exercise habits separately from tea drinking practices.

Diverse Outcomes Across Different Cancers

As you sip your tea, think about this: not all cancers act the same way. Your lifestyle and genes play big roles in this story of health. Dark teas like Pu’er might help shield you from cancer's reach by calming inflammation that can light a fire under tumour growth. 
These dark leaves bring more to the fight – they push back against destructive free radicals with their antioxidant might. Obesity is another foe, hiking up cancer risk through flames of chronic swelling within our bodies. Yet here too, studies hint at dark tea as an ally that could lower fats in blood—stepping into the battle against obesity’s grip on sickness rates. 
For real protection across different body parts and illnesses, though, we need more clear evidence; human trials are key to confirming these hopeful signs seen so far, mostly in labs or animals alone.

Considerations for Daily Consumption Levels

When you choose to drink tea daily, think about how much. Most individuals in the United States and United Kingdom sip black tea often. In China and Japan, green is the top choice; a bit of oolong or white teas get drunk worldwide. 
The good stuff in your cup comes from how long you brew it, what kind you pick, plus the heat. Hot brewed cups pack more punch than iced or instant kinds, which have fewer benefits because they may not use real brewed leaves. Adding juice cuts down on these perks too.
Can Tea Be Bad for Your Health?
This would be the next question that comes to your mind. Well, most teas are good, but the FDA weighed on this by sending out warnings about those so-called dieter’s teas that pack in aloe, senna, buckthorn, and other plant-derived laxatives.
Since tea contains caffeine just like other caffeinated beverages, you might then ask if it has the same effect as with these beverages. The answer is yes, the effect could range from restlessness, tremors, abdominal pain, tachycardia, palpitations, headache, diarrhea, and even vomiting. However, there is a tiny bit of documentation that says it would be a big risk on the health of an adult if he takes a moderate amount of caffeine – about 300 mg-400 mg (approximately 6 mg per kilogram body weight) in a day.
A research by Health Canada finalized that consuming caffeine in a moderate amount of about 400 mg per day did not show any side effects or threats to the health of adults. The amount of caffeine in tea differs by their type. It is a little bit higher in black tea, ranging from 64-112 mg per 8 fl oz serving. The oolong tea follows suit in terms of caffeine quality. Having about 29 to 53 mg per 8 fl oz serving. White and Green teas contain slightly less (32-37 mg per 8 fl oz serving, and 24-9 mg per 8 fl oz serving, respectively.) For Decaffeinated teas, they have less than 12 mg per 8 fl oz serving. 
Now that we have talked about the adults, what about the children? Sadly, the study on the effects in children is limited. On a general note, taking caffeine that is less than 3.0 mg per kg body weight has not given adverse effects in children. But when in higher doses, some behavioral effects could be noticed, such as sleep disturbances, anxiety, and increased nervousness.
According to the food agency, consumers should be very careful of herb-containing supplements that state on their label that it battles cancer and take them away as pain relievers. Know that none of their claims are backed by facts and science. Therefore, care should be taken as some of these herbs have led to kidney and liver damage and bowel problems. In some cases, even death.
The FDA warns against taking so-called supplements that include:
  • Germander
  • Lobelia
  • Willow bark
  • Chaparral
  • Comfrey
  • Ephedra
Let's put all these scary warnings aside for a minute. Those who plan and conduct food service or nutritional programs, yes, the nutritionists, have advised us to drink up and make merry of the benefits that come with drinking tea.
However, go easy with decaf versions; they've lower health-boosting bits called catechins—important players for your body's guard against harm like UV rays and maybe even tumours. Not all teas are alike when we chat about their power to fend off illness—and sipping them does hold some risks if overdone (think upset stomachs). Stick within limits that keep things safe without losing out on those pluses tied to a well-made brew. 

Navigating Myths About Teas Healing Powers

Many people believe tea can heal. Not every drink called "tea" has caffeine, though. Only those with black, green or white on the box are true teas; matcha is just green in powder form.
Processing matters—green stops oxidizing early, while black goes all the way before drying. Think of oxidation like a clock: less time means less caffeine for your cup. Green often lands at that lower end, and black tops it off with more buzz. 
These leaves come packed with antioxidants known to tackle harmful free radicals causing inflammation and cell trouble inside you. Yet don't bank on them as cancer shields—the evidence isn't solid enough yet to say so definitively, but having plant-based foods such as these doesn’t hurt either! That's in your cup of green but remember—all kinds have some antioxidant power worth noting even if they're not equal after decaf strips some away during its process. 
Herbal mixes aren't real tea—they lack both leaf origin and jolt from caffeine—but may still do good things since plants lend their perks here too (think calming L-theanine found occasionally). Tisane’s the word used technically for herbals; chamomile or peppermint types fall under this umbrella without strict ties to tradition.

What is the National Cancer Institute (NCI) take on using tea to prevent cancer?

This research institution, NCI, is known for developing evidence-based research results for others to make plain. The National Cancer Institute, NCI generally does not advocate specific dietary or medical interventions. However, the documentation, as stated above, regarding the probable advantages and benefits of drinking tea in line with cancer prevention is, at this time, inconclusive. You will know why in the next section.
Putting It All Into Perspective
When you think about tea's role in cancer prevention, keep it real. Studies show promise yet tell us to be cautious. Green tea often steals the spotlight with compounds that may slow cancer growth, but results aren't clear-cut or universal across types of cancers or populations.
Experts suggest a few cups each day could do some good and likely won't harm - just don't count on it as your shield against cancer alone. Remember balance; healthy living includes more than what's in your cup. It takes regular check-ups, exercise, plus avoiding tobacco and too much sun to really stack the deck in your favor against this disease.


Tea's role in cancer prevention remains debated. Studies show potential benefits, mainly from green tea compounds. Yet, the evidence isn't conclusive due to varying research quality and results. 
While some patterns suggest protective effects, you must consider factors such as lifestyle and genetics too. Ultimately, enjoy tea as part of a balanced diet, but know that it may offer just one piece of the complex puzzle of reducing cancer risk.


1. Yuan, Jian-Min, et al. “Tea and Cancer Prevention: Epidemiological Studies.” Pharmacological Research, vol. 64, no. 2, Aug. 2011, pp. 123–135

2. “Cancer-Preventive Potential of White Tea.” ScienceDaily,Accessed 28 Mar. 2024.

3. Yang, Chung S., et al. “Antioxidative and Anti-Carcinogenic Activities of Tea Polyphenols.” Archives of Toxicology, vol. 83, no. 1, 12 Nov. 2008, pp. 11–21

4. Mao, Xiangbing, et al. “Tea and Its Components Prevent Cancer: A Review of the Redox-Related Mechanism.” International Journal of Molecular Sciences, vol. 20, no. 21, 23 Oct. 2019, pp. 5249–524

5. Edgar, Julie. “Types of Teas and Their Health Benefits.” WebMD, WebMD, 20 Mar. 2009,

6. “Health Benefits of Tea? Here’s What the Evidence Says.” The New York Times, 5 Oct. 2015

7. “Can Drinking Tea Improve Cognition, Immunity, and More?”, 3 May 2022
Article by
Charles M. Carlsen
Hello! I'm Charles, As co-founder of Drsono, I contribute to the DRSONO blog, providing valuable insights and up-to-date information on ultrasound technology and diagnostic imaging.

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