Overview
People have been drinking infusions of tea for thousands of years, beginning in China and India. Today, tea is consumed more widely than any other beverage in the world except water. Billions of people drink tea, and a large number of studies show that tea has many health benefits.
There are three main varieties of tea: green, black, and oolong. All three varieties are made from the leaves of the same species of plant called Camellia sinensis; the difference is in how the tea leaves are processed. Green tea is made from unfermented leaves, while oolong tea is made from partially fermented leaves and black tea is fully fermented.
Green tea is one of the healthiest beverages you can consume. It’s sugar free, doesn’t have any calories, and is loaded with antioxidants that provide copious health benefits. Plus, it’s refreshing. What’s not to like?
Active Ingredients
Green tea contains a number of bioactive compounds including caffeine and other alkaloids, polyphenols, and Vitamin K, and after steeping many of the bioactive compounds in the tea leaves effuse into the final drink.
The main stimulants in green tea include caffeine, theobromine, and theophylline. On the other hand, L-theanine, an amino acid found in green tea, has a calming effect on the nervous system. So green tea can have a mildly stimulating but also relaxing effect at the same time.
Green tea also contains a high concentration of powerful antioxidants called polyphenols. In fact, many of the health properties of green tea are attributed to its polyphenol content. Green tea has a higher polyphenol content than black or oolong, as fermenting tea leaves lowers the polyphenol content.
The polyphenols in green tea, which include multiple subcategories of polyphenols like flavonoids and catechins, can reduce the formation of free radicals in the body, protecting cells, molecules, and other structures from damage. One of the most active and powerful antioxidant polyphenols in green tea is epigallocatechin-3-gallate (EGCG). EGCG has been studied to treat a wide variety of diseases and may be one of the main reasons green tea has such powerful medicinal properties. Beyond EGCG, other polyphenol catechins in green tea include catechin, gallocatechin, epicatechin, epigallocatechin, and epicatechin gallate.
Tea leaves contain a higher percentage of caffeine by weight than coffee beans. However, because a lot less tea leaves are used to make tea than coffee beans are used to make coffee, a cup of tea has significantly less caffeine than a cup of coffee.
Drinking green tea has a long list of health benefits. In fact, research shows it can help you:
1. Improve Brain Function And Mental Performance
While the stimulants in tea can keep you awake, they can also make your brain function better. The main stimulant, caffeine, is present in tea at enough of a dose to provide a lift for most people without causing the increased anxiety and “jitters” associated with too much coffee.
In the brain, the main method of action of caffeine is to block adenosine receptors, allowing neurons to fire for longer, increasing brain activity. Studies have shown caffeine improves concentration and memory.
Additionally, the amino aide L-theanine has a relaxing effect while simultaneously increasing alertness, which, in combination with caffeine, can increase brain function and help you be more productive.
2. Protect Your Brain And Prevent Cognitive Decline
Not only can drinking green tea improve brain function in the short term, it may also protect your brain in the long term. In particular, data show it may help stave off Alzheimer’s and Parkinson’s diseases.
Alzheimer’s disease is the most common neurodegenerative disease and a leading cause of dementia. Parkinson’s disease is the second most common neurodegenerative disease, resulting in the death of dopamine-producing neurons in the brain.
Multiple studies show that the antioxidant catechins in green tea can have a protective effect on neurons, potentially lowering your risk of Alzheimer’s and Parkinson’s diseases.
3. Burn Fat
Clinical studies suggest that green tea may boost your metabolism and help you burn fat. Yes, the benefits of green tea include helping you lose weight and lower your risk of becoming overweight or obese. Much of this effect is likely due to caffeine, but other compounds in tea may also contribute to this effect. By helping you selectively burn the fat you have stored in your body for energy, green tea may help you feel fuller and maintain a more steady energy level, resulting in less hunger cravings and less calories consumed.
In particular, one randomized controlled 12 week study of 240 men and women showed the group that received green tea extract had significant decreases in body weight, body fat percentage, body fat mass, waist circumference, hip circumference, and areas of fat throughout the body.
4. Lower Your Risk Of Type II Diabetes
Type II diabetes is a disease that has reached epidemic proportions over the past few decades and now afflicts hundreds of millions of people worldwide. And yet, it is almost completely preventable and mostly reversible in its early stages by strictly cutting the intake of sugar (carbohydrates).
Diabetics lose their sensitivity to insulin, which means insulin is less effective in signaling to cells to absorb sugar from the blood stream, resulting in both higher blood sugar and higher blood insulin levels. Because both sugar and insulin are damaging to the cardiovascular system, over time many adverse effects result. (The more sensitive you are to insulin, and in general the lower your normal blood sugar level, the better.)
Green tea can lower and help stabilize your blood sugar levels (glucose levels); in fact, studies show that green tea can even improve insulin sensitivity and reduce blood sugar levels. One study among Japanese individuals found that those who drank the most green tea had a very significantly lower risk of developing type II diabetes. Other studies have shown similar results.
5. Maintain A Healthy Cardiovascular System
Cardiovascular diseases, which lump heart disease, stroke, and other diseases of the heart and blood vessels caused by atherosclerosis and hypertension (high blood pressure) into one category, are the most prevalent causes of death in the world. Studies show that green tea can improve some of the main risk factors for these diseases, which includes helping regulate total cholesterol, LDL cholesterol, and triglycerides. One method by which green tea might help: it significantly increases the antioxidant levels of your blood, protecting LDL cholesterol particles from oxidation—one of the causes of heart disease.
Studies have shown green tea drinkers have a lower risk of cardiovascular disease. Other studies show that black tea has similar effects. In fact, researchers estimate that the rate of heart attack decreases measurably with the consumption of just a few cups of tea per day.
Research also shows that green tea lowers total cholesterol, improving the overall cholesterol profile. One population-based clinical study found that men who drink green tea are more likely to have lower total cholesterol than those who do not drink green tea. Other clinical studies that look at populations of people indicate that the antioxidant properties of green tea may help prevent atherosclerosis, particularly coronary artery disease. The benefits of green tea also seem to extend to preventing stroke, reducing high blood pressure, and inhibiting the formation of blood clots. Much of the effect may also be due to the ability of green tea to help lower blood sugar and insulin levels.
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6. Boost Your Physical Performance
Green tea health benefits also seem to include boosting physical performance, increasing exercise endurance, and decreasing reaction time, and there are many, many such studies showing these effects from caffeine, although other ingredients in green tea may aid this effect. Caffeine, and green tea’s, ability to mobilize fatty acids in fat tissue to make them more easily available for use as energy also seems to aid physical performance. In one study, caffeine was shown to significantly increase physical performance (exercise endurance and exertion). The antioxidants in green tea may also help prevent tissue damage during physical exertion as well.
7. Lower Your Risk Of Various Types Of Cancers And Diseases
Several population-based clinical studies have shown that both green and black teas may help protect against cancer. Early clinical studies suggest that the polyphenols in tea, especially green tea, may play an important role in the prevention of cancer. Researchers also believe that polyphenols help kill cancerous cells and stop them from growing.
It is well known that oxidative damage contributes to the development of cancer and that antioxidants can have a protective effect. Green tea is an excellent source of powerful antioxidants, so it’s logical that tea could reduce your risk of cancer.
According to the National Cancer Institute, the polyphenols in tea have been shown to decrease tumor growth in both animal and laboratory studies. Researchers believe that it is the high level of polyphenols in tea that help kill cancerous cells and stop them from growing, although the exact mechanism by which tea inhibits and prevents cancerous cells is uncertain.
Breast Cancer
A meta-analysis of observational studies found that women who drank the most green tea had a lower risk of developing breast cancer: the most common form of cancer in women.
Pancreatic Cancer
One large-scale clinical study compared green tea drinkers with non-drinkers and found that those who drank the most tea were less likely to develop pancreatic cancer, particularly women, who were 50% less likely to develop the disease.
Prostate Cancer
Prostate cancer is the most common type of cancer in men. One study found that men drinking five or more cups of green tea had only about half the risk of developing advanced prostate cancer as those that drank less than one cup per day.
Colorectal Cancer
A study of 69,710 Chinese women found that green tea drinkers had a much lower risk of developing colorectal cancer.
While they don’t prove cause and effect, multiple other observational studies have shown that green tea drinkers are significantly less likely to get various types of cancer than those that don’t drink green tea.
Studies have also shown the positive impacts of green tea on bladder, ovarian, esophageal, lung, skin, and stomach cancer.
Furthermore, drinking green tea may help prevent liver disease.
8. Improve Your Dental Health
Some studies show that the catechins in green tea can kill bacteria and inhibit viruses like the influenza virus, potentially lowering your risk of infections.
One of the primary species of harmful bacteria in the mouth is Streptococcus mutans. It causes plaque formation and is a leading contributor to cavities and tooth decay. Studies show that the catechins in tea can inhibit the growth of Streptococcus mutans.
In general, green tea consumption is associated with improved dental health and a lower risk of dental caries.
On top of that, another benefit of green tea is that it can reduce bad breath.
9. Prevent Infection And Illness
Since some of the bioactive compounds in green tea are anti-viral and anti-bacterial, in much the same way as green tea can kill bacteria in your mouth, it can also inhibit bacteria and viruses in your bloodstream and throughout the rest of your body. Similarly, green tea may inhibit viral and bacterial infection via your nasal passages. All this means that green tea may help prevent colds and the flu, and furthermore seems to be able to alleviate the symptoms of colds and the flu once you are sick.
10 Aid Digestion
Among all these green tea health benefits: some data have shown green tea can aid digestion, improve bowel health, and reduce IBD (Inflammatory Bowel Disease). Green tea may act by reducing inflammation in the gut associated with Crohn’s disease and ulcerative colitis, the two types of IBD.
11. Improve Bone Mineral Density
There is some data to suggest drinking green tea may make your bones stronger. This may be because it is alkaline-forming in your body, helping prevent the leaching of minerals from your bones to counteract blood acidity and maintain proper blood pH.
12. Hydrate
Tea doesn’t dehydrate. Even though it is a commonly-held belief that anything with caffeine is dehydrating, this is false.
Yes, caffeine is a diuretic, but water is also a diuretic. The volume of water of a cup of tea overcomes any dehydrating effect from the caffeine in the tea.
In fact, it would take an excessive amount of caffeine in a drink to dehydrate. The amount of water in tea, and even coffee, makes these drinks hydrating; substantiating this point, tests have shown that tea is not significantly different than water in the maintenance of hydration.
So why not have a cup of tea: a terrifically hydrating drink of water with healthy compounds mixed in to boot?
13. Improve Your Mood And Help You Relax
The amino acid L-theanine in green tea increases the activity of the inhibitory neurotransmitter GABA, which has anti-anxiety effects. L-theanine also increases dopamine and the production of alpha waves in the brain, aiding relaxation, decreasing stress, and helping reduce depression.
14. Ameliorate The Symptoms Of Arthritis
Another green tea health benefit: some of the compounds in green tea are anti-inflammatory, and there is evidence to suggest their anti-inflammatory effects can improve the symptoms of arthritis.
15. Maintain Healthy, Youthful-Looking Skin
Green tea can prevent wrinkles and the signs of aging because the antioxidants in green tea are able to fight free-radical damage. Similarly, the anti-inflammatory properties of green tea can help prevent damage to skin from all sorts of harmful environmental stressors.
Additionally, green tea can help relieve psoriasis by reducing the redness and irritation that comes with it; green tea has also been shown to reduce the redness that comes with rosacea.
16. Support Your Skin During Sun Exposure
The polyphenols in green tea, especially EGCG, have been shown to have a particularly powerful effect in supporting skin cells and cellular DNA in the presence of sunlight. May different clinical studies have shown EGCG to help promote the skin’s defenses against the sun’s rays. And because these polyphenols accumulate in the skin, regularly drinking green tea or taking a green tea supplement with EGCG can act as supplemental protection.
17. Live Longer
Drinking green tea can lead to a higher quality life and a reduced risk of dying from any cause. Of course, since green tea drinkers are at a lower risk of cardiovascular disease and various cancers over a given period of time, it makes sense that green tea could help you live longer.
In a decade-long study of Japanese adults, death from all causes together, and also death from specifically heart disease and stroke, were all reduced in both women and men who drank the most green tea (5 or more cups per day) versus those who drank less than one cup per day. Another study found that those who drank the most green tea were 76% less likely to die during the 6 year study period.
Forms
Drink green tea you prepare: to gain the benefits of green tea it’s best to make tea from loose-leaf tea leaves. But there are also powders and supplements you can take, such as green tea extract, that contain some or all of the active ingredients.
When drinking green tea, just be sure you don’t add sugar, which could undo the positive benefits of your cup of tea. And milk may reduce the antioxidant capacity of tea.
The more you can use green tea to replace other sweet drinks–like soft drinks, energy drinks, and sugary beverages–the better!
Precautions
Green tea contains tannins, which can decrease the absorption of iron and folic acid. As such, it may be better for women who are pregnant or breastfeeding to abstain. People who are anemic should be careful drinking tea around mealtime.
Those taking anticoagulant drugs such as warfarin (Coumadin, Jantoven) should drink green tea with caution due to its vitamin K content, which is necessary for blood coagulation.
People who have anxiety or are very sensitive to caffeine should also be cautious drinking green tea.
Studies in laboratory animals have found that green tea polyphenols inhibit the growth of esophageal cancer cells (in line with its anti-cancer properties). Other clinical studies have found that green tea offers protection against the development of esophageal cancer, particularly among women. However, one large-scale population-based clinical study found just the opposite: drinking green tea was associated with an increased risk of esophageal cancer, and the stronger and hotter the tea, the greater the risk. It seems that if the water is very hot, it can damage the esophagus and lead to long-term adverse consequences. So just make sure the tea you drink isn’t extremely hot.
Summary
There are so many benefits of green tea. Feel better, lose weight, lower your risk of chronic diseases, and be healthier by making green tea a regular part of your life!
Additional References
Caffeine and sports activity: a review
Neurological mechanisms of green tea polyphenols in Alzheimer’s and Parkinson’s diseases
Potential Therapeutic Properties of Green Tea Polyphenols in Parkinson’s Disease
Anticariogenic effects of green tea
Protective effects of dietary chamomile tea on diabetic complications
L-Theanine reduces psychological and physiological stress responses
A green tea extract high in catechins reduces body fat and cardiovascular risks in humans
EGCG inhibits growth, invasion, angiogenesis and metastasis of pancreatic cancer
