Green tea has been spoken about as the panacea for pretty much every disease or condition that has been in the news over the last ten or so years. Its properties have been investigated to try to confirm the health benefits in relation to cancers, heart disease and stroke. In addition it is said to have an input in lowering cholesterol, preventing diabetes, removing fat and warding off dementia.
But how much of what we read and hear is true? Well Katherine Tallmadge, RD, LD, a nutritionist and spokeswoman for the American Dietetic Association, says, "I believe in green tea based on everything written about it". She goes on to say that she likes all teas, black, green and white.
Yet within the medical and scientific community there is a view that any research carried out into the health benefits of green tea has yet to be rigorously tested within the research community. The benefits presently being ‘seen’ are generally still at the laboratory stage. Any other benefits noted could easily be contributed to because of other lifestyle factors. Cardiologist Nieca Goldberg, MD, is a spokeswoman for the American Heart Association and medical director of the New York University Women's Heart Center, and she points out that large scale human trials are not common and have generally been conducted in the East. This means that the research is investigating people who take green tea as part of their diet, but these same people take soy protein and eat a lot of fish, two factors known to reduce the risk of heart disease and some cancers.
However Goldberg does concede that any trials conducted have produced promising outcomes and she does agree with other health experts who tell us that green tea has healthy antioxidants and compounds which help the body to remain healthy.
Antioxidant Rich Green Tea
The name given to green tea’s antioxidants is catechins. As with any antioxidants these remove free radicals in the body which are suspected of damaging DNA which leads to cancers, atherosclerosis and blood clots. Green tea is in one of a group of foodstuffs known to be high in antioxidants, other foodstuffs include, berries, red wine, grapes and dark chocolate.
The amount of green tea which must be consumed to achieve any benefit is still open to discussion. However because it has concentrated EGCG (epigallocatechin-3-gallate), a form of catechins, produced by the minimal processing the tea is subjected to, it is perceived as beneficial in any amounts. The optimal amount per day has yet to be identified. The question of how much should be consumed per day is important because EGCG is beneficial to the body in the correct amounts but with too much it cannot be used.
Tak-Hang Chan, PhD, is a professor emeritus in the department of chemistry at McGill University in Montreal. He has carried out research with a synthetic form of EGCG which gave positive results when used to shrink prostrate cancer tumors in mice. He sums up by saying, "We must overcome the issue of poor bioavailability [and other issues] in order to get the most out of their benefits".
Although Chan’s finding provides hope for the future, the American Cancer Society's strategic director of nutritional epidemiology, Marji McCullough, ScD, RD adds a note of caution. She points out that human studies have not yet managed to replicate the findings achieved in the laboratory. The ECGC in green tea may halt or reduce cancer growth by killing cells which have in some way mutated and are growing in an unexpected manner, but as yet it is only a theory.
She then talks of some of the problems which must be overcome, "Epidemiologically, one of the challenges is finding populations that drink enough green tea and have for a long time. With cancer, it's always difficult to find the exposure time, or the point at which cancer cells begin to develop”.
Although McCulluch is rightly careful in her comments there does appear to be more evidence relating to the positive aspects of green tea. Two studies both from the East, one from Japan and the other from China appear to show that drinking green tea twice a day can inhibit the growth of cancer.
The Japanese study involved almost 500 Japanese women with stage 1 and stage 2 breast cancer. The study found that there was a lower re-occurrence of cancers in those women who drank increased amounts of green tea before and after surgery.
In China it was found that increased green tea consumption meant that the risk of developing prostrate, stomach, esophageal, pancreatic and colorectal cancer was reduced.
More recently 22 studies were analyzed with the aim of identifying the association between the risk of developing lung cancer and green tea consumption. The conclusion was that the risk of developing lung cancer could be reduced by 18% by consuming an additional two cups of green tea per day.
Green Tea can Protect Your Heart
It appears that green tea may be good for your heart. However the numbers of epidemiological studies relating to green tea and heart conditions are very few and their results are conflicting.
One Japanese study found that consuming at least four cups of green tea everyday may reduce the severity of coronary heart disease amongst the male participants. However the study was small scale with 500 Japanese men and women involved.
In Holland, one study had in excess of 3,000 men and women, and it found that the amount of blockages in the blood in the heart’s blood vessels was less, particularly in women.
Experts are aware that lifestyle and diet influence any outcomes from studies. However Goldberg notes that green tea's antioxidants are dilators. This she says, means that they increase the state of blood vessels and inhibits clogging. This effect can also be produced by antioxidant-rich blueberries and pomegranates.
She says, "I think people should know these are important studies, that everyday foods that are an option may actually have health benefits" .Goldberg then explains why green tea is not at the top of the doctor’s list of treatments, "I think green tea, because of its antioxidant value, may have heart benefits, but it's not something we regularly prescribe to people, because there isn't as much evidence as there is in exercise's ability to improve heart health".
Green Tea as a Weight Loss Tool
Two separate, but small scale and limited studies have found that green tea can be beneficial in lowering LDL, also known as bad cholesterol, and can help to lower levels of obesity. Obesity and high LDL are known risks factors for stroke, heart disease and diabetes. The studies were conducted in Japan and Holland.
The Dutch research identified that drinking more caffeinated green tea increased weight loss. They also noted that those drinking decaffeinated green tea cut the inches from the waistline too.
In Japan the study involved 240 men and women and each was given a different amount of green tea extract for a period of three months. Those who had been given the most had lost the highest amount of body fat and weight. They also had lower LDL levels and lower blood pressure.
Green Tea – How do you take yours?
Weight loss supplements that have green tea extracts as an ingredient can be dangerous if you have liver problems, but people with no liver problems should be fine. However the best way to take green tea is to drink it.
Diane McKay, PhD, is a Tufts University scientist who studies antioxidants, and she says, "Taken altogether, the evidence certainly suggests that incorporating at least a few cups of green tea every day will positively affect your health. It's not going to cure anything and it shouldn't be consumed as a drug, but it can complement the rest of the diet". But she also stresses the importance of eating a healthy balanced diet of fruits, vegetables, grains, seeds, and nuts, but you can indulge yourself with as much green tea as you want.
She ends cautiously by saying, "I don't think it can hurt to drink it. I'd focus on dietary sources rather than supplements because there are several compounds in green tea that might need to be consumed together. We just don't know yet".