Wednesday, October 16, 2013

Why You Should Be Drinking More Green Tea: Several Studies Showing Positive Results for Weight Loss, Cancer Prevention, Disease Resistance, and More...

Among all the beverages available for consumption by humans, tea is the most popular drink in the world, second only to water.  While a majority of that tea is generally black tea--made from the fermented leaves of the Camellia sinensis bush--an increasing amount of people are trying out green tea.  Green tea is also made out of the leaves of the Camellia sinensis bush, but the leaves are only dried and heated, not fermented.  It has a relatively similar flavor, it comes from the same plant, it is just as easy to prepare, and it may have benefits that are not realized from drinking black tea.

Camellia sinensis
Although I have heard purported positive health effects from drinking green tea from friends, family, co-workers, television ads and fitness/nutritional websites, I decided to take a look at the research myself to see what science has to say about it.  Despite many trials finding little to no effect, there are quite a few studies showing very real positive benefits from drinking this simple beverage.

Now, I love knowing the science behind how things work, especially nutritional science.  However, I encourage anyone who drinks tea or is thinking about drinking tea make the switch to green tea, despite what the research shows.  It tastes great and it's cheap, easy to find and easy to make.  I have always enjoyed southern-style "Sweet Tea," and using green tea as a base for this drink is great, since you get the taste of black tea with the added benefit of nutrients and polyphenols in green tea.

With that said, let's look at some of the research.


Cancer

Green tea has long been thought to reduce, eliminate or shrink cancer cells.  Green tea has been especially touted for helping to treat specific types such as prostate, ovarian and pancreatic cancer.

A review of scientific evidence conducted by researchers at Tokushima Bunri University in Japan found that drinking 10 cups of green tea per day (defined in Japan as ten 200 ml tea cups, or eight American cups) delayed cancer onset for up to 7 years in women.  Drinking the same amount of tea, with the addition of a green tea extract supplement, significantly reduced the formation of colon tumors.  Finally, the same researchers suggest that the combination of green tea and anti-cancer drugs may be more effective than just drugs alone.

Another group of researchers from the Shanghai Cancer Institute in China conducted a study of about 1000 healthy people and another 1000 people with pancreatic cancer.  The researchers followed these two groups of people and collected information on their tea drinking habits.  After collecting the data, they found that the people who reported drinking the most green tea had the least risk of developing pancreatic cancer.  Women specifically showed a 32% decrease in the risk of developing this form of cancer.  The researchers also determined that the temperature of the tea also had an effect on the risk of developing this form of cancer, with the people who drank the tea at a lower temperature having a lower risk of cancer than those who drank it at a higher temperature... independent from the amount of tea drank.  While this study cannot determine causation (meaning it cannot prove green tea reduced the risk of pancreatic cancer, since the data was collected from participant surveys), it is still an important base for future research on the (hopefully) positive effects on cancer risk by drinking green tea.

Next up, scientists from the Laval University Cancer Research Center in Quebec, Canada reviewed the evidence for the reduced risk of ovarian cancer from drinking green tea.  The review consisted of over 20 articles and 5 epidemiological studies on the effects of green tea on ovarian cancer.  The review implies that components of green tea reduced or destroyed ovarian cancer cells when put together in a test tube environment outside of the human body.  Inside an actual human body, observational evidence suggests that green tea offers significant protection against ovarian cancer, and the prognosis for ovarian cancer patients is less severe for those who drink green tea versus those that don't.

Reduce your risk of cancer with green tea
Finally, a study conducted by the Case Western Reserve University in Cleaveland, Ohio set out to find the mechanisms behind the reduced risk of prostate cancer from green tea consumption.  The team discovered that green tea works in two ways to fight prostate cancer: activation of a particular gene known as p53, which is known as a tumor suppressing gene, and through a previously unknown pathway which occurred independently of the p53 gene, causing cancer cells to initiate a process called apoptosis... basically meaning the cancer cell commits suicide.  The researchers conclude that drinking green tea may provide additional benefit for men with prostate cancer who are already taking anti-cancer drugs.

All of these reviews/studies suggest that drinking green tea may help prevent developing certain types of cancers, and provide additional positive effects for those who already have cancer and are taking anti-cancer drugs.

Exercise, Weight Loss, and Insulin Control

There is no shortage on supplements featuring green tea as one of the main active ingredients, if not the only ingredient.  And for good reason.  There are numerous studies devoted to figuring out the connection between green tea, exercise, weight loss and insulin sensitivity.

First up, we have a study conducted by the good folks at Lund University in Sweden, who tried to determine the effects of green tea on blood sugar levels, insulin and hunger.  14 healthy individuals were randomly assigned to drink either 1 and a half cups of green tea or water, while consuming a simple breakfast of white bread and turkey slices.  Although the scientists discovered no benefit on insulin or blood sugar levels from drinking the green tea, the group that drank the green tea reported significantly higher satiety from the meal.  This means the people in the green tea group felt much fuller and satisfied after eating than the group that just drank water.  Thus, the researchers concluded that green tea could be helpful in reducing the amount of food people ingest, reducing calorie intake and thereby causing weight loss.  Green tea could prove helpful for those who find dieting difficult due to increased hunger.

Another study done by scientists at the Sao Lucas Hospital in Brazil tried to determine the effect of green tea on elderly patients with metabolic syndrome, characterized by high blood sugar levels, high levels of abdominal fat, unusually high resistance to insulin, and high blood pressure and cholesterol readings.  45 patients were assigned to one of two groups: one group drank 3 cups of green tea per day for 60 days, the other group ate and drank normally (control).  After collecting the data from the 60 days, researchers discovered that the health parameters of either group of metabolic syndrome patients did not change.  However, the green tea group actually lost a bit of weight, a significant amount of it coming from abdominal fat.  The study concluded that although no health parameters changed, green tea could be useful in helping reduce weight of patients of metabolic syndrome, which is one factor in reducing the risk for other ailments, including Type-2 diabetes.

No longer an "ancient Chinese secret"
A study conducted by the Tokohu University Graduate School of Medicine in Japan attempted to determine the correlation between green tea consumption and "functional disability," meaning they tried to find an association between drinking green tea and developing degenerative diseases like osteoporosis, or having a debilitating stroke.  The sent questionnaires to over 13,000 people to determine green tea consumption and other lifestyle factors over a 3 year period.  After collecting all the data, the researchers determined that green tea had a protective effect on people who drank the most green tea.  Drinking more green tea, up to 5 cups a day, provided a significant benefit against functional disability versus drinking no green tea at all... even after adjusting for other lifestyle factors.

Next, we have a yet another study done by the people of Brazil, this time by the scientists of Sao Paulo University.  They attempted to determine the effects of green tea on body composition of 4 different groups of females: a placebo group, a green tea drinking group, a weight training placebo group, and a weight training + green tea drinking group.  Not surprisingly, the placebo group showed no differences in weight loss or muscle gain throughout the trial.  The green-tea-only group fared a bit better, maintaining their muscle mass and losing a bit of weight, although their metabolisms slowed down a bit.  Both the resistance training groups lost weight, increased their strength, lean body mass (muscle), and their metabolic rate.  However, the group that drank green tea while also weight lifting showed even more positive results than the weight-lifting-only group, suggesting that green tea has some kind of anabolic, or muscle-building, effect.

Brazil is on a roll with their studies on green tea.  Another study out of this country, this time carried out by the Federal University of Santa Catarina, investigated the effects of green tea on the bodily stress levels on 14 young men doing a resistance training program.  Although the study was only conducted for 7 days, the scientists reported that the oxidative stress levels of subjects ingesting about three cups of green tea per day were less than those who drank only water.  This study suggests that green tea may have a protective effect against damage induced by intense exercise, although the authors point out that the participants had a very "unbalanced" diet (meaning they didn't eat the healthiest diet during the trial).  Additional studies are needed to confirm if the green tea further protects against oxidative damage in people with nutritionally-sufficient diets.

Finally, to top it all off, the Chinese Medical Nutrition Research Center in Chongqing, China, set out to determine the effect of green tea on glucose control and insulin resistance in the human body.  In this review, 17 trials comprised of over 1,100 subjects were studied to find an answer.  After reviewing all the data, the researchers concluded that green tea has favorable effects on reducing blood sugar levels in the body, an important risk factor for developing metabolic syndrome and Type 2 diabetes.

Disease Resistance

Not too many studies in this area of green tea research, but one particular study, conducted by the University of Florida, attempted to determine if a specific formula of green tea provided resistance from bacterial and viral infection.  In this study, healthy adults were separated into two groups. One taking a green tea capsule supplement, twice a day, for 3 months.  The other taking nothing, serving as a control group.

After the 3 month trial, the researchers found out that the group taking the green tea supplement had significantly less flu and cold symptoms than the control group, and when they did get sick, the symptoms were less severe and lasted a shorter period of time compared to control.

Green tea may help fight off infections

In addition, the green tea supplement group had increased levels of T-cells in their bodies compared to the control group.  T-cells are part of the system of defense our bodies use to prevent us from getting sick from infections.  Increasing the T-cell count would, theoretically, increase our resistance against sickness, which this study seems to confirm.

The researchers concluded that this particular formulation of green tea helped reduce the incidence of cold and flu symptoms.  Although not specifically mentioned in the study, I believe that the benefits of this formulation could just as easily come from a simple cup or two of plain old green tea.

Oral Health

Among the mounds of research being conducted on the associations between green tea and health factors, we have a study from the Israel Institute of Technology which tried to find an interaction between green tea and oral health.  They found that the main polyphenol in green tea, known as EGCG, significantly increases the activity of oral peroxidases, which are the natural defense mechanisms in our mouth that protect from oral diseases, most notably gingivitis.  This finding suggest that drinking green tea may be helpful for preventing, or even treating, gum disease and cavities.  In a sugary beverage-laden world, it's nice to see that green tea may have the opposite effect than most other beverages consumed in America today... increasing the protection from cavities and gum disease instead of decreasing it.

Conclusion

I started this article with a bit of apprehension, as many things people have told me are "healthy" are not necessarily proven by research to be as healthy for people as claimed.  However, the scientific literature seems to suggest that green tea may be beneficial for folks who are already healthy, as well as people suffering from (or at risk of) strokes, osteoporosis, dementia, obesity, insulin resistance, various types of cancers, cellular oxidative damage from intense exercise, and even cavities and gingivitis!  Green tea may even provide your immune system with a boost during the cold and flu season.

It's tea, not pee!

If you aren't already drinking green tea on a regular basis, maybe you should try it out!  It tastes great, it's completely vegetarian, and it's loaded with nutrients that are probably (-definitely-) very beneficial to human health.  Now excuse me while I brew up some green tea for myself!

ADDENDUM 12/31/2013

Recently, I've been learning about a group of substances knows as "nootropics," which is a general term for compounds that may increase cognitive function (in layman's terms, that means it makes your brain work better).

According to the Reddit.com Nootropics FAQ, L-Theanine is a compound found in the tea leaf that is extremely safe for consumption, but also reduces the negative side effects of caffeine while promoting its positive aspects.  Although black tea officially has more L-Theanine than green tea, green tea still contains some of this particularly interesting compound... in the range of 10-20mg per cup.  Higher quality loose leaf green teas supposedly contains even more L-Theanine than pre-bagged green tea, although I haven't found evidence supporting this claim.

Anyway, a dose of L-Theanine capable of noticeably improving cognitive function is as low as 100mg, or approximately 4 to 5 cups of green tea--assuming a 20mg extraction per cup.  Such doses have shown to improve attention span when completing a difficult mental task, and also reduce mental fatigue when taken in combination with caffeine.  This page provides links to several studies which show these positive benefits of L-Theanine.

So, in addition to all the anti-cancer and anti-obesity/diabetes benefits from drinking green tea, this wonderful drink may also improve your brain power as well!  People who might benefit from drinking 4 to 5 cups of green tea include students preparing to study for difficult tests, people with mentally-intensive jobs such as accountants and administrators, and anyone who would generally like better mental performance in every day life (which could include practically anyone and everyone).

To be fair, all of these studies have tested L-Theanine and caffeine as stand-alone supplements, not from consumption of green tea.  The ratio to L-Theanine and caffeine in the studies is mostly reversed, as well.  There is generally more caffeine than L-Theanine when extracted from a green tea brew, whereas in these studies, the reverse was true... more L-Theanine than caffeine.  However, although I have no scientific references to support my view, I believe drinking enough green tea will still confer the same cognitive benefits as taking the equivalent pill form of L-Theanine... plus all the benefits of other anti-oxidants and phytonutrients/polyphenols that are in green tea.

The amount of life-improving advantages to drinking green tea, to me, is nothing short of amazing.  What are you waiting for?!  Go brew some green tea!

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