Cancer is a dreaded diagnosis, but we probably have a lot more ability to prevent cancer than we think. In fact, scientists estimate that almost 80 percent of cancers are caused by or worsened by negative influences in our lifestyles, including smoking, obesity, inactivity and alcohol.
Poor diet is an especially big culprit, perhaps even bigger than smoking – up to 35 percent of cancer may be due to dietary excesses and deficiencies, especially deficiencies of essential nutrients coupled with excesses of nutrient-poor processed foods.
The good news is that we can choose foods and beverages that are cancer-protective, such as green tea. Green tea contains a number of important chemicals that may work to halt cancer growth, including polyphenols such as catechins; EGCG is probably the best known of the catechins. Many studies have suggested that green tea consumption can lower the risk of multiple cancers, including cancers of the pancreas, colon, stomach, ovary, bladder and prostate.
A recent study by Dr. Susanne Henning at UCLA looked at the impact of green tea consumption on PSA levels in 67 men with prostate cancer before they went in for surgery. Half of the men drank 6 cups of green tea per day for three to eight weeks before surgery while the other half drank water instead.
At the time of surgery, the men who had been drinking the green tea had significantly lower blood PSA levels than the control group, and PSA protein in the prostate tissue was also lower.
In addition, inflammatory markers in the prostate were significantly lower in the green tea group; this is important, because inflammation is known to increase cancer cell growth. There was no difference between the two groups in terms of tumor cell growth itself, but keep in mind that this was also a relatively short study. An Italian study done in 2006 showed that men with precancerous changes in their prostate glands were significantly less likely to progress to prostate cancer when they took green tea extract capsules for one year.
Green tea seems to inhibit cancer in multiple ways: It reduces free radicals and DNA damage while also increasing DNA repair. It also encourages cancer cells to die rather than replicate, and it reduces the ability of cancer cells to grow and spread to other tissues.
In all likelihood, it can work synergistically with cancer protective chemicals in other foods, like the glucosinolates in broccoli and other cruciferous vegetables. Studies have suggested that consumption of at least five 4-ounce cups of green tea every day are needed for the best cancer protective effect, though even one cup per day may provide some benefit.
Are there side effects to drinking green tea? Some people may be sensitive to the caffeine in tea, especially if drinking large amounts which can lead to GI upset, anxiety and palpitations; decaffeinated green tea is an option in this case – some studies suggest that decaffeinated green teas have just as much benefit as the caffeinated varieties.
Brewing also makes a difference – you'll get the highest extraction of those healthy polyphenols if you brew the leaves in near-boiling water and let the tea steep for at least 10 minutes before drinking.
And, if you need more reasons to try green tea, consider that it may also help to lower your cholesterol, prevent heart disease, reduce your blood sugar, lower your risk of colitis, improve your arthritis, and help you lose weight – all of that in a cup of little green leaves! So the next time you're in line at Starbucks, consider going for the green tea instead of that cup o' Joe.