VUlogo

Psychology Department

Health Psychology Home Page

Papers written by students providing scientific reviews of topics related to health and well being

  HomeWeight LossAlternative Therapy | Supplements | Eating Disorders | Fitness | About this Page |

 

It’s Tea Time: The Health Benefits and Weight Loss Secrets Behind Green Tea

Rebecca Dobler

October 5, 2009

http://www.mellowmonk.com/images/green_tea_service.jpg

 

 

 

Introduction

According to the U.S. Department of Health and Human Services, nearly two thirds of all American adults are overweight or obese.  About half of those people fall under the obese category by having a body mass index (BMI) of 30 or higher (http://win.niddk.nih.gov/statistics/).  The obesity prevalence is continuing to increase not only among adults, but among children as well.  It is considered to be an epidemic and many lives are being put in danger because overweight and obese people are at an increased risk for diseases such as type II diabetes, heart disease, and cancer (http://www.cdc.gov/obesity/causes/health.html). 

What can be done to prevent this obesity epidemic?  People need to focus more on their eating and exercise, as these are two of the core components to weight loss.  As people lose weight, they will become less and less vulnerable to diseases like type II diabetes that are associated with obesity.  However, in today’s fast paced, high stress, and on-the-go society, people struggle to find time.  Healthy eating is often forgotten about and people just grab some food on the go.  Also, because they are so busy, exercise is more often than not neglected from our daily schedules.   People are always searching for a new diet, the latest eating trend, or the newest fad to help them lose as much weight as they can.  Although many of those fad diets and infomercial pills will not work, one thing that will help you to be a more healthy person is green tea (Camellia sinensis).  People should still include healthy eating habits and exercise in their daily lives, however, green tea has been used for thousands of years, and those who drink green tea are found to have a lower weight, a reduced risk to diseases, and overall better health.

The Secrets Behind Green Tea

It is no secret that green tea has many benefits to offer.  The Chinese and Indians were the first to discover these benefits of green tea.  Green tea dates back to nearly 5,000 years ago when it was used in ancient China and India (http://www.umm.edu/altmed/articles/green-tea-000255.htm).  It was and still is used today as a natural remedy and form of traditional Chinese medicine to help with bodily processes and health such as healing wounds, improving heart health, and the promotion of digestion.  However, one may wonder how a simple leaf is capable of having so many health benefits.

There are three main types of teas, which include green, oolong, and black tea.  Green tea is the least processed of the three and therefore provides the greatest health benefits and the most antioxidants, which are due to the polyphenols in the leaves.  The most important polyphenol in green tea is called epigallocatechin-3-gallate (EGCG), as it contains the most catechins (http://www.whfoods.com/genpage.php?tname=foodspice&dbid=146#nutritionalprofile).

In addition to the antioxidants, green tea also contains alkaloids such as theobromine, theophylline, and caffeine, which provide stimulant effects.  Amino acid compounds are also present which has a calming effect on the nervous system.  These compounds, plus many more, all interact to create effects such as weight loss, decreased risk for diseases, and a calming effect on the body’s nervous system.

Why Go Green?

Go Green to Lose Weight

One of green tea’s greatest health benefits is weight loss.  Green tea induces thermogenesis (heat production) in the cells to enhance energy expenditure and stimulate weight loss.  Not only does it promote fat loss, but also it also specifically targets the fat that lines the abdominal region and fat around the intestines, which is called viscera fat.  This viscera fat can also lead to type II diabetes and put people at an increased risk for metabolic syndrome, so the consumption of green tea can also help to reduce these diseases (http://www.whfoods.com/genpage.php?tname=foodspice&dbid=146#nutritionalprofile).

In addition to thermogenesis within the cells and weight loss, green tea also helps to increase exercise endurance so one can get more out of a workout.  In one study, green tea extract was given to lab rats and scientists analyzed the amount of time the rats could swim before becoming exhausted.  Over the course of a ten-week period, the amount of time the rats could swim before getting tired increased by as much as 24% (www.whfoods.com).  This increased endurance is due to green tea’s catechins which stimulate the use of fatty acids by the liver and muscle cells.  This means that the body has more time before using the glycogen storage (carbohydrates that are stored and ready for use during exercise).  However, it was also found that green tea must to be consumed on a regular basis to have this effect, and drinking it right before exercise will not make a significant difference. 

Go Green to Reduce Risk of Cardiovascular Disease

Text Box: http://nutritionresearchcenter.org/healthnews/wp-content/uploads/2008/07/tea_plantation.jpgAnother one of green tea’s potential health benefits is the prevention of cardiovascular disease.  According to one study in The American Family Physician, “women who consumed five or more cups a day had a 31% lower risk of dying from cardiovascular disease” (p. 592).  Another study showed the same results in women, and a 22% lower risk of dying from cardiovascular disease in men with the consumption of five or more cups of green tea per day.  A different study published in January 2005 in the American Journal of Clinical Nutrition divided 38 men into two different groups.  One of the groups drank a 1 bottle of green tea a day which contained 690 mg of antioxidant catechins, and the other group drank 1 bottle of oolong tea with 22 mg of catechins.  However, after this trial, the men drinking the green tea lost more fat, weight, and the amount LDL cholesterol damaged by free radicals decreased significantly.  This is important for cardiovascular disease because green tea helps to prevent the oxidation reactions of green tea circulating around the bloodstream, which is a contributing factor to cardiovascular disease (www.whfoods.com).  Some studies, however, provide uncertain results, and debate whether or not green tea actually helps decrease the risk of cardiovascular disease.  In spite of this, there are very few harmful effects or downsides to drinking green tea, so even if studies are providing a variety of results, drinking green tea can only do good for the body!

Go Green to Prevent Cancer

http://www.esleconf.org/images/lemon.jpg

 
Green tea is also known to help reduce the risk of getting cancer.  Studies show that cancer rates are lower in Asian countries like Japan where green tea consumption is a regular part of the day.  Many studies have been conducted which showed that the consumption of green tea can lead to a decreased risk of cancers such as oral cancer, breast cancer, ovarian cancer, prostate cancer, and many more.  For example, the intake of 4-6 cups a day can help prevent oral cancer.  The antioxidants in the polyphenols rid the mouth of the free radicals and oxidants, which are potentially cancerous cells with, mutated genes (http://www.healingdaily.com/conditions/green-tea-for-cancer.htm).  Studies also show that oral cancer rates in China are about half of what they are in the United States due to the increased green tea consumption in China. 

Consumption of green tea may also lead to a decreased risk of breast cancer in woman.  A Japanese study found with 472 females found that women in the early stages of cancer who drank at least five cups a day were less likely to experience recurrences of the disease after finishing the treatment.  However, no improvement was seen in women in the later stages of cancer.  Much of the data was inconclusive, but if green tea has any sort of potential benefit, then people should drink it because it might decrease their risk of developing an illness.  It was also found that woman with ovarian cancer survived longer with the illness if they regularly drank green tea than those who did not consume green tea (http://www.umm.edu/altmed/articles/green-tea-000255.htm).  In addition, green tea may have an effect on the development of prostate cancer in men.  Laboratory studies done in test tubes have shown that green tea extracts will inhibit the growth of prostate cancer cells.  Researchers also found that the risk of prostate cancer declined with increasing frequency as more green tea was consumed for longer periods of time. 

Caffeine in Green

Many people in today’s society are set in their caffeinated ways: they depend on a cup of coffee in the morning to wake them up for classes or work; they need that mid morning pick-me-up to power through the next few hours until lunch; another cup in the afternoon is absolutely necessary to make it through the end of the day; and one last cup o’ Joe is needed to finish that late night studying.  But is all that coffee really necessary?  There are other alternatives to keep energy levels high than just depending on caffeine from coffee.  You guessed it – that other alternative is green tea!  You might be thinking that it does not have nearly enough caffeine in it to make it through the day, but that should not hold people back from drinking green tea.  Each cup of coffee has between 90 and 150 mg of caffeine, and each cup of tea has between 30 and 70 mg of caffeine.  About two cups of green tea will yield the same amount of caffeine as one cup of coffee.  If people drink green tea instead of coffee, they will not only get the same caffeine stimulant that they get from coffee, but they will also receive the added health benefits that come with the consumption of green tea.  Want one more reason to drink green tea? A Japanese study showed that subjects who drank one cup of tea per day had a 38% decrease in cognitive impairment, that this protective effect was not found in coffee or black tea consumption (http://www.lef.org/magazine/mag2008/apr2008_New-Research-On-The-Health-Benefits-Of-Green-Tea_01.htm). 

The Downsides to Going Green

By this point, you might be wondering why the negative aspects of drinking green tea have not been discussed.  The negative aspects have not been mentioned because there are very few downsides to drinking green tea.  Although many of the studies have yielded inconclusive results, very few have come up with any negative aspects to green tea.  There are, however, a few downsides, but they rarely actually affect people.  According to the University of Maryland, drinking too much green tea can stimulate the body with too much caffeine and my be irritable, experience insomnia, dizziness, or heart palpitations.  Pregnant women are also advised to stay away from green tea, as drinking too much of it can cause neural tube defects in their babies.  In addition, green tea combined with medications will occasionally cause problems.  For example, green tea combined with chemotherapy drugs has been shown to make the cancer cells less sensitive to the chemotherapy (http://www.umm.edu/altmed/articles/green-tea-000255.htm).  However, one must keep in mind that people have been drinking green tea for thousands of years both as a cultural tradition and for the health benefits associated with the drink.  There have been very few instances where green tea has actually had a negative impact on a person. 

Green Tea’s Benefits: Fact or Fiction?

While all of the claims being made have been from reputable web sites and articles, the real facts lie in the clinical trials and studies published in peer reviewed medical literature.  Several journal articles have been analyzed to confirm the beneficial health effects that come from consuming green tea. 

Fact: Green Tea Enhances Exercise Induced Weight Loss

Farmer, Katsuragi, Maki, Matsuo, Reeves, Yasunaga, & et al (2008, August 14) studied the relationship between green tea catechins, body composition, and fat distribution during exercise induced weight loss in overweight and obese adults.  The trial was conducted at two different sites as a randomized, double blind, and controlled clinical trial.  It included overall healthy, but sedentary men and women as the participants.  Exclusion groups included pregnant women, people with a BMI less than 25, recent weight loss, or people with eating disorders.  Inclusion factors required people to be between 21 and 65 years of age, and the subjects had to agree to drink no more than 2 caffeinated drinks per day.  Once subjects were selected, they were randomly divided into two groups.  One group was given a beverage with green tea extract and 625 mg of catechins, which are found in green tea, or they were given a control beverage with water and artificial flavoring.  The two beverages looked identical so staff and participants could not tell the difference.  Subjects were told to drink a 1,500 mL bottle per day within 30 minutes.  Participants of both groups were then told to exercise at a moderate level for at least 180 minutes per week and to go to 3 supervised exercise sessions per week.  Factors such as study beverage compliance, physical activity and exercise tests, dietary intake, body weight and waist circumference, body composition and abdominal fat areas, and serum lipids were some factors that were considered at baseline and when assessing the changes from baseline.  It was found that subjects in the catechin green tea group all had significant decreases in total fat mass, total abdominal fat area, subcutaneous fat area, and intra-abdominal fat area.  However, the control group had a much smaller decrease, and even an increase in the subcutaneous fat area.  There were no negative side effects during this study.  This study shows that with the intake of a beverage containing green tea catechins, exercise induced loss of abdominal fat may be increased. 

Fact: Green Tea Reduces Cardiovascular Risk

http://www.mellowmonk.com/labels/green%20tea%20in%20the%20news.html

 
Basu, & Lucas, (2007, August) conducted a study with 240 men and women with mild-moderate hypercholesterolemia who were already following a low-fat diet, but were at risk for cardiovascular disease.  Participants were either given 375 mg of a green tea extract or a placebo and took the supplement daily over the course of twelve weeks.  After the twelve-week supplements were completed, it was found that LDL cholesterol levels were significantly lower in the tea intervention group than when the groups started at baseline.  LDL levels were reduced by 11-16% with a p-value of less than .01, which makes the data very significant.  The placebo group, however, yielded zero changes in LDL levels, showing that green tea does have an effect on reducing risks of cardiovascular disease. 

Fact: Green Tea Reduces Cancer Risk

Chen, Dai, Lu, Shrubsole, Shu, Zheng, & et al (2009, February) conducted a case-control study and looked at the relationship between the consumption of green tea and the risk of developing breast cancer.  The study was done in Shanghai, China during August 1996-March 1998 and again from April 2002-February 2005.  Cases were found by using the Shanghai Cancer Registry, and there were 3454 cases in this study and 3474 controls.  Controls had the same criteria as the cases with the exception of a breast cancer diagnosis.  Inclusion criteria was female, between the ages of 25 and 70 years, no previous history of cancer, and the female had to be a resident of urban Shanghai.  Controls were randomly selected using the Shanghai Resident Registry and were frequency matched by age.  Participants were asked if they drank tea regularly (2 or more times per week for 3 months straight), what kind of tea they consumed, the age at which they began drinking tea, the total number of years of consumption, how often they changed the tea leaves, and the amount of tea leaves used per cup.   The study showed that women who drank green tea on a regular basis had a 12% and significantly lower risk for developing breast cancer.  It was also found that among premenopausal women, beginning to drink green tea at an earlier age yielded a decreased risk of developing breast cancer.

Fact: Green Tea is good for every part of you!

Research by Clement, Yuri (2009, May 22) assessed overall clinical evidence of green tea and health benefits. Pubmed and the Cochrane Library were searched for peer reviewed journal articles about clinical trials and studies conducted pertaining to green tea dating up to April 2009.  It was found that the antioxidants in green tea have chemoprevention and disease-modifying properties, which have been linked to, lowered oxidative stress levels.  Decreased oxidative stress levels are also linked to a lower incidence of neurodegenerative diseases and a decreased aging process.  Clement also found many studies, which looked at the anti-obesity effects of green tea.  One study in particular was a randomized and double blind controlled trial done over the course of a 12-week period.  There were 17 treated subjects and 18 control subjects, and it was found that green tea caused a significant reduction in body weight and other anthropometric measures.  These findings were confirmed in another similar trial, but this time with 240 subjects.  The larger trial also found green tea to cause a decrease in systolic blood pressure and LDL cholesterol as well. 

An observational study conducted in Japan followed 40,530 people for 11 years who habitually drank green tea.  A significant reduction in the risk of cardiovascular disease was found amongst these subjects.  This decrease in the risk of cardiovascular disease showed a decrease in the risk of strokes as well in a follow up study. 

http://www.mellowmonk.com/labels/green%20tea%20in%20the%20news.html

 
Clement also researched another observational study, which showed that green tea has a protective factor against prostate cancer.  Prostate cancer in Chinese men showed a significant decrease in cancer risk between the controls and the green tea treatment subjects.  The study included 49,920 Japanese men who were followed for 14 years to yield these preventative findings. 

Clement’s findings are of significant value because many different studies were assessed, and several found green tea to have beneficial health results.  Habitual green tea consumption is found to reduce the risk of many diseases, obesity, cardiovascular disease, and LDL cholesterol levels.

Is Green Tea the Drink for You?

Green tea has demonstrated benefits and offers those to both healthy people and people who could use a jumpstart to get back on a healthy track.  It can do something for nearly every aspect of your health and body, and green tea also has very few negative side effects.  And even if you claim you don’t like the taste of green tea there are no excuses because there are safe and effective green tea supplement pills containing catechin and the antioxidants that will help the body.  There is a great deal of evidence and clinical trials, which show the beneficial effects of green tea on weight loss, cancer prevention, and decreasing cardiovascular risk.  While one will not want to totally rely on green tea as their only form of health or disease intervention, green tea will not hurt the body and will only help.  Despite the inconclusive results of some studies, most studies have shown a positive correlation between drinking green tea and a healthier body.  Drinking green tea will just about always do something good for the body and a person’s health! 

 

 


References

(2002). Green tea beneficial for oral cancer?  Retrieved September 27, 2009, from http://www.healingdaily.com/conditions/green-tea-for-cancer.htm

 (2007, May).  Statistics Related to Overweight and Obesity.  Retrieved September 25, 2009, from the U.S. Department of Health and Human Services site: http://win.niddk.nih.gov/statistics/

(2009, August 19).  Overweight and Obesity Health Consequences.  Retrieved September 25, 2009, from the Center for Disease Control site: http://www.cdc.gov/obesity/causes/health.html

(2009).  Green Tea.  Retrieved September 26, 2009, from http://www.whfoods.com/genpage.php?tname=foodspice&dbid=146#nutritionalprofile

Basu, Arpita, & Lucas, E.A.  (2007, August).  Mechanisms and Effects of Green Tea on Cardiovascular Health.  Nutrition Reviews, 65(8), 361-375.  Retrieved from Pubmed database. 

Chen, Z., Dai, Q., Lu, W., Shrubsole, Martha J., Shu, X.O., Zheng, Y., & et al  (2009, February).  Drinking Green Tea Modestly Reduces Breast Cancer Risk.  The Journal of Nutrition, 139(2), 310-316.  Retrieved from Pubmed database. 

Clement, Yuri.  (2009, May 22).  Can Green Tea do that? A literature review of the clinical evidence.  Preventative Medicine, 49(2009), 83-87.  doi:10.1016/j.ypmed.2009.05.005

Farmer, M., Katsuragi, Y., Maki, K.C., Matsuo, N., Reeves, M.S., Yasunaga, K. , & et al (2008, August 14).  Green Tea Catechin Consumption Enhances Exercise-Induced Abdominal Fat Loss in Overweight and Obese Adults.  The Journal of Nutrition, 264-270. doi:10.3945/jn.108.098293.

Goepp, Julius.  (2008, April).  New Research on the Health Benefits of Green Tea.  Retrieved September 25, 2009, from   http://www.lef.org/magazine/mag2008/apr2008_New-Research-On-The-Health-Benefits-Of-Green-Tea_01.htm

Hawkins, Earnest B.  (2007, November). Green tea.  Retrieved September 26, 2009, from the University of Maryland Medical Center site: http://www.umm.edu/altmed/articles/green-tea-000255.htm

Schneider, Craig, & Segre, Tiffany.  (2009).  Green Tea: Potential Health Benefits.  American Family Physician, 79(7), 591-594.  Retrieved from Pubmed database. 

 

 

 

VUlogo

Psychology Department

The Health Psychology Home Page is produced and maintained by David Schlundt, PhD.
  

me

VuLogoVanderbilt Homepage

Return to the Health Psychology Home Page
Send E-mail comments or questions to Dr. Schlundt