10 Darn Good Reasons to Drink Green Tea
By Kris Gunnars
Green tea is the healthiest beverage on the planet. It is loaded with antioxidants and nutrients that have powerful effects on the body. This includes improved brain function, fat loss, a lower risk of cancer and many other incredible benefits. Here are 10 health benefits of green tea that have been confirmed in human research studies.
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1. Green Tea Contains Various Bioactive Compounds That Can Improve Health
Green tea is more than just green liquid. Many of the bioactive compounds in the tea leaves do make it into the final drink, which contains large amounts of important nutrients.
It is loaded with polyphenols like flavonoids and catechins, which function as powerful antioxidants. These substances can reduce the formation of free radicals in the body, protecting cells and molecules from damage. These free radicals are known to play a role in aging and all sorts of diseases. One of the more powerful compounds in green tea is the antioxidant Epigallocatechin Gallate (EGCG), which has been studied to treat various diseases and may be one of the main reasons green tea has such powerful medicinal properties.
Green tea also has small amounts of minerals that are important for health. Try to choose a higher quality brand of green tea, because some of the lower quality brands can contain excessive levels of fluoride. That being said, even if you choose a lower quality brand, the benefits still far outweigh any risk.
2. Compounds in Green Tea Can Improve Brain Function and Make You Smarter
Green tea does more than just keep you awake, it can also make you smarter. The key active ingredient is caffeine, which is a known stimulant. It doesn't contain as much as coffee, but enough to produce a response without causing the “jittery" effects associated with too much caffeine. What caffeine does in the brain is to block an inhibitory neurotransmitter called Adenosine. This way, it actually increases the firing of neurons and the concentration of neurotransmitters like dopamine and norepinephrine. Caffeine has been intensively studied before and consistently leads to improvements in various aspects of brain function, including improved mood, vigilance, reaction time and memory.
However… green tea contains more than just caffeine. It also has the amino acid L-theanine, which is able to cross the blood-brain barrier. L-theanine increases the activity of the inhibitory neurotransmitter GABA, which has anti-anxiety effects. It also increases dopamine and the production of alpha waves in the brain. Studies show that caffeine and L-theanine can have synergistic effects. The combination of the two is particularly potent at improving brain function. Because of the L-theanine and the smaller dose of caffeine, green tea can give you a much milder and different kind of “buzz" than coffee. Many people report having more stable energy and being much more productive when they drink green tea, compared to coffee.
3. Green Tea Increases Fat Burning and Improves Physical Performance
If you look at the ingredients list for any fat burning supplement, chances are that green tea will be on there. This is because green tea has been shown to increase fat burning and boost the metabolic rate in human controlled trials.
In one study of 10 healthy men, green tea increased energy expenditure by 4 percent. Another study showed that fat oxidation was increased by 17 percent, indicating that green tea may selectively increase the burning of fat. However, I'd like to point out that some studies on green tea don't show any increase in metabolism, so the effects may depend on the individual.
Caffeine itself has also been shown to improve physical performance by mobilizing fatty acids from the fat tissues and making them available for use as energy. In two separate review studies, caffeine has been shown to increase physical performance by 11-12 percent, on average.
4. Antioxidants in Green Tea May Lower Your Risk of Various Types of Cancer
Cancer is caused by uncontrolled growth of cells. It is one of the world's leading causes of death. 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 makes perfect sense that it could reduce your risk of cancer, which it appears to do:
- Breast cancer: A meta-analysis of observational studies found that women who drank the most green tea had a 22 percent lower risk of developing breast cancer, the most common cancer in women.
- Prostate cancer: One study found that men drinking green tea had a 48 percent lower risk of developing prostate cancer, which is the most common cancer in men.
- Colorectal cancer: A study of 69,710 Chinese women found that green tea drinkers had a 57 percent lower risk of colorectal cancer.
Multiple other observational studies show that green tea drinkers are significantly less likely to get various types of cancer. It is important to keep in mind that it may be a bad idea to put milk in your tea, because it can reduce the antioxidant value.
5. Green Tea May Protect Your Brain in Old Age, Lowering Your Risk of Alzheimer's and Parkinson's
Not only can green tea improve brain function in the short term, it may also protect your brain in old age. Alzheimer's disease is the most common neurodegenerative disease in humans and a leading cause of dementia. Parkinson's disease is the second most common neurodegenerative disease and involves the death of dopamine producing neurons in the brain. Multiple studies show that the catechin compounds in green tea can have various protective effects on neurons in test tubes and animal models, potentially lowering the risk of Alzheimer's and Parkinson's.
6. Green Tea Can Kill Bacteria, Which Improves Dental Health and Lowers Your Risk of Infection
The catechins in green tea have other biological effects as well. Some studies show that they can kill bacteria and inhibit viruses like the influenza virus, potentially lowering your risk of infections.
Streptococcus mutans is the primary harmful bacteria in the mouth. It causes plaque formation and is a leading contributor to cavities and tooth decay. Studies show that the catechins in green tea can inhibit the growth of streptococcus mutans. Green tea consumption is associated with improved dental health and a lower risk of caries.
7. Green Tea May Lower Your Risk of Type II Diabetes
Type II diabetes is a disease that has reached epidemic proportions in the past few decades and now afflicts about 300 million people worldwide. This disease involves having elevated blood sugar levels in the context of insulin resistance or an inability to produce insulin. Studies show that green tea can improve insulin sensitivity and reduce blood sugar levels.
One study in Japanese individuals found that those who drank the most green tea had a 42 percent lower risk of developing type II diabetes. According to a review of 7 studies with a total of 286,701 individuals, green tea drinkers had an 18 percent lower risk of becoming diabetic.
8. Green Tea May Reduce Your Risk of Cardiovascular Disease
Cardiovascular diseases, including heart disease and stroke, are the biggest causes of death in the world. Studies show that green tea can improve some of the main risk factors for these diseases. This includes total cholesterol, LDL cholesterol and triglycerides.
Green tea also dramatically increases the antioxidant capability of the blood, which protects the LDL cholesterol particles from oxidation, which is one part of the pathway towards heart disease. Given the beneficial effects on risk factors, it is not surprising to see that green tea drinkers have up to a 31 percent lower risk of cardiovascular disease.
9. Green Tea Can Help You Lose Weight and Lower Your Risk of Becoming Obese
Given that green tea can boost the metabolic rate in the short term, it makes sense that it could help you lose weight. Several studies show that green tea leads to decreases in body fat, especially in the abdominal area. One of these studies was a randomized controlled trial in 240 men and women that went on for 12 weeks. In this study, the green tea group had significant decreases in body fat percentage, body weight, waist circumference and abdominal fat. However, some studies don't show a statistically significant increases in weight loss with green tea, so this needs to be taken with a grain of salt.
10. Green Tea May Decrease Your Risk of Dying and Help You Live Longer
Of course, we all have to die eventually. That is inevitable. However, given that green tea drinkers are at a lower risk of cardiovascular disease and cancer, it makes sense that it could help you live longer. In a study of 40,530 Japanese adults, those who drank the most green tea (five or more cups per day) were significantly less likely to die during an 11 year period:
- Death of all causes: 23 percent lower in women, 12 percent lower in men.
- Death from heart disease: 31 percent lower in women, 22 percent lower in men.
- Death from stroke: 42 percent lower in women, 35 percent lower in men.
Another study in 14,001 elderly Japanese individuals aged 65-84 found that those who drank the most green tea were 76 percent less likely to die during the six year study period.
This article was reposted with permission from our media associate Authority Nutrition.
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By Ana Maldonado-Contreras
- Your gut is home to trillions of bacteria that are vital for keeping you healthy.
- Some of these microbes help to regulate the immune system.
- New research, which has not yet been peer-reviewed, shows the presence of certain bacteria in the gut may reveal which people are more vulnerable to a more severe case of COVID-19.
You may not know it, but you have an army of microbes living inside of you that are essential for fighting off threats, including the virus that causes COVID-19.
How Do Resident Bacteria Keep You Healthy?<p>Our immune defense is part of a complex biological response against harmful pathogens, such as viruses or bacteria. However, because our bodies are inhabited by trillions of mostly beneficial bacteria, virus and fungi, activation of our immune response is tightly regulated to distinguish between harmful and helpful microbes.</p><p>Our bacteria are spectacular companions diligently helping prime our immune system defenses to combat infections. A seminal study found that mice treated with antibiotics that eliminate bacteria in the gut exhibited an impaired immune response. These animals had low counts of virus-fighting white blood cells, weak antibody responses and poor production of a protein that is vital for <a href="https://doi.org/10.1073/pnas.1019378108" target="_blank">combating viral infection and modulating the immune response</a>.</p><p><a href="https://doi.org/10.1371/journal.pone.0184976" target="_blank" rel="noopener noreferrer">In another study</a>, mice were fed <em>Lactobacillus</em> bacteria, commonly used as probiotic in fermented food. These microbes reduced the severity of influenza infection. The <em>Lactobacillus</em>-treated mice did not lose weight and had only mild lung damage compared with untreated mice. Similarly, others have found that treatment of mice with <em>Lactobacillus</em> protects against different <a href="https://doi.org/10.1038/srep04638" target="_blank" rel="noopener noreferrer">subtypes of</a> <a href="https://doi.org/10.1038/s41598-017-17487-8" target="_blank" rel="noopener noreferrer">influenza</a> <a href="https://doi.org/10.1371/journal.ppat.1008072" target="_blank" rel="noopener noreferrer">virus</a> and human respiratory syncytial virus – the <a href="https://doi.org/10.1038/s41598-019-39602-7" target="_blank" rel="noopener noreferrer">major cause of viral bronchiolitis and pneumonia in children</a>.</p>
Chronic Disease and Microbes<p>Patients with chronic illnesses including Type 2 diabetes, obesity and cardiovascular disease exhibit a hyperactive immune system that fails to recognize a harmless stimulus and is linked to an altered gut microbiome.</p><p>In these chronic diseases, the gut microbiome lacks bacteria that activate <a href="https://doi.org/10.1126/science.1198469" target="_blank" rel="noopener noreferrer">immune cells</a> that block the response against harmless bacteria in our guts. Such alteration of the gut microbiome is also observed in <a href="https://doi.org/10.1073/pnas.1002601107" target="_blank" rel="noopener noreferrer">babies delivered by cesarean section</a>, individuals consuming a poor <a href="https://doi.org/10.1038/nature12820" target="_blank" rel="noopener noreferrer">diet</a> and the <a href="https://doi.org/10.1038/nature11053" target="_blank" rel="noopener noreferrer">elderly</a>.</p><p>In the U.S., 117 million individuals – about half the adult population – <a href="https://health.gov/our-work/food-nutrition/2015-2020-dietary-guidelines/guidelines/" target="_blank" rel="noopener noreferrer">suffer from Type 2 diabetes, obesity, cardiovascular disease or a combination of them</a>. That suggests that half of American adults carry a faulty microbiome army.</p><p>Research in my laboratory focuses on identifying gut bacteria that are critical for creating a balanced immune system, which fights life-threatening bacterial and viral infections, while tolerating the beneficial bacteria in and on us.</p><p>Given that diet affects the diversity of bacteria in the gut, <a href="https://www.umassmed.edu/nutrition/melody-trial-info/" target="_blank" rel="noopener noreferrer">my lab studies show how diet can be used</a> as a therapy for chronic diseases. Using different foods, people can shift their gut microbiome to one that boosts a healthy immune response.</p><p>A fraction of patients infected with SARS-CoV-2, the virus that causes COVID-19 disease, develop severe complications that require hospitalization in intensive care units. What do many of those patients have in common? <a href="https://www.cdc.gov/mmwr/volumes/69/wr/mm6912e2.htm" target="_blank" rel="noopener noreferrer">Old age</a> and chronic diet-related diseases like obesity, Type 2 diabetes and cardiovascular disease.</p><p><a href="http://doi.org/10.1016/j.jada.2008.12.019" target="_blank" rel="noopener noreferrer">Black and Latinx people are disproportionately affected by obesity, Type 2 diabetes and cardiovascular disease</a>, all of which are linked to poor nutrition. Thus, it is not a coincidence that <a href="https://www.cdc.gov/mmwr/volumes/69/wr/mm6933e1.htm" target="_blank" rel="noopener noreferrer">these groups have suffered more deaths from COVID-19</a> compared with whites. This is the case not only in the U.S. but also <a href="https://www.washingtonpost.com/world/europe/blacks-in-britain-are-four-times-as-likely-to-die-of-coronavirus-as-whites-data-show/2020/05/07/2dc76710-9067-11ea-9322-a29e75effc93_story.html" target="_blank" rel="noopener noreferrer">in Britain</a>.</p>
Discovering Microbes That Predict COVID-19 Severity<p>The COVID-19 pandemic has inspired me to shift my research and explore the role of the gut microbiome in the overly aggressive immune response against SARS-CoV-2 infection.</p><p>My colleagues and I have hypothesized that critically ill SARS-CoV-2 patients with conditions like obesity, Type 2 diabetes and cardiovascular disease exhibit an altered gut microbiome that aggravates <a href="https://theconversation.com/exercise-may-help-reduce-risk-of-deadly-covid-19-complication-ards-136922" target="_blank" rel="noopener noreferrer">acute respiratory distress syndrome</a>.</p><p>Acute respiratory distress syndrome, a life-threatening lung injury, in SARS-CoV-2 patients is thought to develop from a <a href="http://doi.org/10.1016/j.cytogfr.2020.05.003" target="_blank" rel="noopener noreferrer">fatal overreaction of the immune response</a> called a <a href="https://theconversation.com/blocking-the-deadly-cytokine-storm-is-a-vital-weapon-for-treating-covid-19-137690" target="_blank" rel="noopener noreferrer">cytokine storm</a> <a href="http://doi.org/10.1016/S2213-2600(20)30216-2" target="_blank" rel="noopener noreferrer">that causes an uncontrolled flood</a> <a href="http://doi.org/10.1016/S2213-2600(20)30216-2" target="_blank" rel="noopener noreferrer">of immune cells into the lungs</a>. In these patients, their own uncontrolled inflammatory immune response, rather than the virus itself, causes the <a href="http://doi.org/10.1007/s00134-020-05991-x" target="_blank" rel="noopener noreferrer">severe lung injury and multiorgan failures</a> that lead to death.</p><p>Several studies <a href="https://doi.org/10.1016/j.trsl.2020.08.004" target="_blank" rel="noopener noreferrer">described in one recent review</a> have identified an altered gut microbiome in patients with COVID-19. However, identification of specific bacteria within the microbiome that could predict COVID-19 severity is lacking.</p><p>To address this question, my colleagues and I recruited COVID-19 hospitalized patients with severe and moderate symptoms. We collected stool and saliva samples to determine whether bacteria within the gut and oral microbiome could predict COVID-19 severity. The identification of microbiome markers that can predict the clinical outcomes of COVID-19 disease is key to help prioritize patients needing urgent treatment.</p><p><a href="https://doi.org/10.1101/2021.01.05.20249061" target="_blank" rel="noopener noreferrer">We demonstrated</a>, in a paper which has not yet been peer reviewed, that the composition of the gut microbiome is the strongest predictor of COVID-19 severity compared to patient's clinical characteristics commonly used to do so. Specifically, we identified that the presence of a bacterium in the stool – called <em>Enterococcus faecalis</em>– was a robust predictor of COVID-19 severity. Not surprisingly, <em>Enterococcus faecalis</em> has been associated with <a href="https://doi.org/10.1053/j.gastro.2011.05.035" target="_blank" rel="noopener noreferrer">chronic</a> <a href="https://doi.org/10.1016/S0002-9440(10)61172-8" target="_blank" rel="noopener noreferrer">inflammation</a>.</p><p><em>Enterococcus faecalis</em> collected from feces can be grown outside of the body in clinical laboratories. Thus, an <em>E. faecalis</em> test might be a cost-effective, rapid and relatively easy way to identify patients who are likely to require more supportive care and therapeutic interventions to improve their chances of survival.</p><p>But it is not yet clear from our research what is the contribution of the altered microbiome in the immune response to SARS-CoV-2 infection. A recent study has shown that <a href="https://doi.org/10.1101/2020.12.11.416180" target="_blank" rel="noopener noreferrer">SARS-CoV-2 infection triggers an imbalance in immune cells</a> called <a href="https://doi.org/10.1111/imr.12170" target="_blank" rel="noopener noreferrer">T regulatory cells that are critical to immune balance</a>.</p><p>Bacteria from the gut microbiome are responsible for the <a href="https://doi.org/10.7554/eLife.30916.001" target="_blank" rel="noopener noreferrer">proper activation</a> <a href="https://doi.org/10.1126/science.1198469" target="_blank" rel="noopener noreferrer">of those T-regulatory</a> <a href="https://doi.org/10.1038/nri.2016.36" target="_blank" rel="noopener noreferrer">cells</a>. Thus, researchers like me need to take repeated patient stool, saliva and blood samples over a longer time frame to learn how the altered microbiome observed in COVID-19 patients can modulate COVID-19 disease severity, perhaps by altering the development of the T-regulatory cells.</p><p>As a Latina scientist investigating interactions between diet, microbiome and immunity, I must stress the importance of better policies to improve access to healthy foods, which lead to a healthier microbiome. It is also important to design culturally sensitive dietary interventions for Black and Latinx communities. While a good-quality diet might not prevent SARS-CoV-2 infection, it can treat the underlying conditions related to its severity.</p><p><em><a href="https://theconversation.com/profiles/ana-maldonado-contreras-1152969" target="_blank">Ana Maldonado-Contreras</a> is an assistant professor of Microbiology and Physiological Systems at the University of Massachusetts Medical School.</em></p><p><em>Disclosure statement: Ana Maldonado-Contreras receives funding from The Helmsley Charitable Trust and her work has been supported by the American Gastroenterological Association. She received The Charles A. King Trust Postdoctoral Research Fellowship. She is also member of the Diversity Committee of the American Gastroenterological Association.</em></p><p><em style="">Reposted with permission from <a href="https://theconversation.com/a-healthy-microbiome-builds-a-strong-immune-system-that-could-help-defeat-covid-19-145668" target="_blank" rel="noopener noreferrer" style="">The Conversation</a>. </em></p>
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