Science gives mixed results for health benefits of tea

(Extraído de canada.com)

Tea has a 5,000-year track record as a medicinal herb - that we know of, and it's probably a lot longer. In traditional Chinese medicine tea is used to treat everything from inflammation and fatigue to bladder infection and cancer. It has long been considered a cleansing agent and a mild natural antidepressant.

By Vancouver Sun July 18, 2013

Tea has a 5,000-year track record as a medicinal herb - that we know of, and it's probably a lot longer. In traditional Chinese medicine tea is used to treat everything from inflammation and fatigue to bladder infection and cancer. It has long been considered a cleansing agent and a mild natural antidepressant.

We know that tea supplies about the biggest payload of antioxidants - pound for pound - of just about any food or drink out there. Many of the alkaloids and chemical compounds in tea have proven medicinal uses. So let's look at the science.

Tea contains caffeine, not as much as a cup of coffee, but more than enough to provide a stimulating effect. Tea also contains theanine - an amino acid that is known to change alpha waves in the brain and promote relaxation. That's why a hot cup of tea gives you that rare combination of calm and energy.

Tea also contains theobromine, which has been used for about 100 years to treat edema, high blood pressure and cardiovascular disease. So if the concentrated compounds in tea can be used to treat disease, will drinking a dilute brew in the morning actually make you healthier or help you live longer? There has been promising research into antioxidants called catechins. Studies of lab mice and of real people in the real world suggest that catechins

provide a protective effect against diabetes, stroke, cancer and heart failure. Green Tea catechins lower total cholesterol and bad cholesterol in human trials.

What about the Big C? Plenty of laboratory studies show that chemical compounds in green tea have the potential to fight cancer. Sadly, studies in which people drink green tea show no evidence of a protective effect against stomach or colorectal cancer.

Breast cancer studies looking at green and black tea are a little confusing. Green tea appears to provide a modest protective effect while black tea actually increased the risk of breast cancer.

Before you throw out all your black tea, let me say this: Scientists use carefully designed experimental paradigms and razor-sharp statistical tools to detect very tiny effects, effects so small they might not extend or shorten the life of one person in a thousand.

Individual studies of the same phenomenon often have conflicting results and that is very much the case when it comes to tea. It appears to increase the risk of heart disease in the U.K. while lowering the risk in continental Europe. What that means is that tea alone is unlikely to deliver much benefit all by itself. There's a lot more going on.