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Green tea and broccoli: Unpicking the puzzle

Consumer Reports News: August 07, 2008 10:38 AM

Two research papers made interesting reading this week, for a number of reasons. They looked at how two dietary items, green tea and broccoli, might impact on heart disease and prostate cancer respectively.

Both heart disease and prostate cancer are mammoth diseases. Heart disease kills more men and women in the United States than any other illness, and, after skin cancer, prostate cancer is the most common cancer in American men. It's little wonder that scientists and public health doctors are anxious to find out whether altering what we eat or drink can protect against these diseases.

Unfortunately, there are no clear take-home messages from either of these papers. We can't say yet whether drinking two cups of green tea a day or eating three portions of broccoli a week can help keep these diseases at bay. That's because neither study was of the type to be able to give us definite answers.

The study on green tea was carried out in healthy volunteers. It found that half an hour after having a cup of tea, the blood vessels become slightly more elastic. Ninety minutes later, the blood vessels had returned to their normal state.

For the broccoli study, researchers found that men at risk of prostate cancer who ate about 14 ounces of broccoli a week for a year had more changes in gene activity than those who didn't. The researchers think that the changes they saw could help to protect against prostate cancer.

Both studies hint at a possible link between the foodstuffs and the diseases. But the studies were very small. Just 14 people took part in the green tea study, and 22 men participated in the prostate cancer study, although tissue samples collected from some men couldn't be used.

To give us a definite answer about whether green tea and broccoli offer protection against these diseases, researchers would need to compare a large group of people who drank green tea or ate broccoli regularly with another group who didn't. Researchers would also have to investigate which people actually developed the diseases, rather than simply measure changes in blood vessels or in gene activity. That kind of research has not yet been done.

But these studies are important in their own right. They also serve to remind us that the journey to understanding how disease develops is a long and often painstaking one. For every research study that immediately impacts on how doctors practice medicine, or prompts a change in lifestyle advice from public health officials, there are hundreds, if not thousands, of studies that don't.

While not all research studies grab the headlines or contribute to the simple lifestyle messages we might wish for, many of them help in small ways to unpick the puzzle of health and disease.

Zosia Kmietowicz, patient editor, BMJ Group has partnered with The BMJ Group to monitor the latest medical research and assess the evidence to help you decide which news you should use.

Read more on about heart disease prevention in our Healthy Heart guide, assess your risk for a heart attack (free), and check out our Treatment Ratings for prostate cancer (subscribers only).

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