Just a few more portions of broccoli each week may protect men from prostate cancer, British researchers reported on Wednesday.
The researchers believe a chemical in the food sparks hundreds of genetic changes, activating some genes that fight cancer and switching off others that fuel tumors, said Richard Mithen, a biologist at Britain's Institute of Food Research.
There is plenty of evidence linking a healthy diet rich in fruits and vegetables to reduced cancer risk. But the study published in the Public Library of Science journal PLoS One is the first human trial investigating the potential biological mechanism at work.
"Everybody says eat your vegetables but nobody can tell us why," said Mithen, who led the study. "Our study shows why broccoli is good."
Prostate cancer is the second-leading cancer killer of men after lung cancer. Each year, some 680,000 men worldwide are diagnosed with the disease and about 220,000 will die from it.
Mithen and colleagues split into two groups 24 men with pre-cancerous lesions that increase prostate cancer risk and had them eat four extra servings of either broccoli or peas each week for a year. The researchers also took tissue samples over the course of the study and found that men who ate broccoli showed hundreds of changes in genes known to play a role in fighting cancer. The benefit would likely be the same in other cruciferous vegetables that contain a compound called isothiocyanate, including brussel sprouts, cauliflower, kale, cabbage, arugula, watercress and horseradish, they added.
Broccoli, however, has a particularly powerful type of the compound called sulforaphane, which the researchers think gives the green vegetable an extra cancer-fighting kick, Mithen said.
"When people get cancer some genes are switched off and some are switched on," he said. "What broccoli seems to be doing is switching on genes which prevent cancer developing and switching off other ones that help it spread."
The broccoli eaters showed about 400 to 500 of the positive genetic changes with men carrying a gene called GSTM1 enjoying the most benefit. About half the population have the gene, Mithen said. The researchers did not track the men long enough to see who got cancer but said the findings bolster the idea that just a few more vegetable portions each week can make a big difference.
It is also likely that these vegetables work the same way in other parts of the body and probably protect people against a whole range of cancers, Mithen added.
"You don't need a huge change in your diet," he said. "Just a few more portions makes a big difference."
Dr. Cinque's comments:.....................
Broccoli, which used to be a wintertime vegetable, has become a yearround vegetable, although I still think the best quality occurs in the winter. I am not much of a fan of eating raw broccoli. It's not just because it tastes better cooked, which it does; I also think broccoli digests better cooked. My rule is: if a raw vegetable can be chewed up and liquified in the mouth in a reasonable amount of time, and it loses its grittiness, then it is indeed fine to eat it raw. But if, after ample chewing, it remains gritty, then it's better to cook it. And by that measure, I definitely think that broccoli should be cooked. How long should you cook it? I say: until the grittiness is gone. What's interesting is that the time can vary quite a lot. One sample of broccoli may tenderize in just 5 minutes of steaming; another sample may take 10 minutes. Of course, the stalk, particularly if its thick, may take longer than 10 minutes, but don't overcook the florets for that reason. Simply sever the florets and remove them from the pot as soon as they're done, and let the stalks continue to cook. Thinly slicing a thick stalk will help it to cook faster. Ideally, you want to stop cooking broccoli while it still has a bright green color, which will maximize both the taste and the nutrition. I definitely consider broccoli to be a super-food, and if I were to be limited to only 10 foods for the rest of my life, broccoli would definitely be one of them.