April 3, 2012 (Chicago) -- Here's another reason to eat your broccoli and Brussels sprouts (and maybe some bok choy). Women with breast cancer who eat a lot of cruciferous vegetables may be more likely to live longer and less likely to have their cancer come back, a large study suggests.
"The more cruciferous vegetables you eat, the better off you are," says researcher Sarah J. Nechuta, MPH, PhD, a postdoctoral research fellow at Vanderbilt University in Nashville, Tenn.
It's easy to get 150 grams of these veggies in your diet, Nechuta tells WebMD. A cup of cooked broccoli, cauliflower, Brussels sprouts, mustard greens, cabbage, and kale all weigh about 150 grams.
The study isn’t the first to suggest that eating the crunchy vegetables may benefit women with breast cancer. But it's one of the largest.
The findings were presented here at the annual meeting of the American Association for Cancer Research.
A Cup of Broccoli a Day May Help
They filled out detailed dietary questionnaires when they entered the study and 18 months and 36 months later. Then they were divided into five groups depending on how many cruciferous vegetables they ate.
By about five years after diagnosis, women in the top fifth -- who ate an average of about 150 grams of cruciferous veggies a day -- were 42% less likely to have died from breast cancer and 58% less likely to die from any cause compared to women in the bottom fifth, who ate less than 54 grams a day. And the women in the top fifth were also 19% less likely to have their breast cancer come back.
Here's why the researchers think the vegetables help. Cruciferous vegetables contain high amounts of compounds called glucosinolates. When eaten, they convert to other compounds called isothiocyanates and indoles that have been shown to have many anti-cancer properties in the lab, Nechuta says.
The researchers considered other factors that can affect breast cancer recurrence and survival, including age, stage of cancer, treatments, exercise, and other dietary factors.
You Are What You Eat?
Still, the study doesn't prove that cruciferous vegetables made all the difference. Women who eat a lot of cruciferous vegetables might have other advantages that weren't measured, or a healthier lifestyle overall, says Aditya Bardia, MD, a cancer specialist at Massachusetts General Hospital in Boston.
Another consideration: The Asian diet is quite different from the American diet. Commonly eaten cruciferous vegetables in China include turnips, Chinese cabbage/bok choy and greens, while broccoli and Brussels sprouts are the more commonly eaten cruciferous vegetables in the United States and other Western countries, Nechuta says.
Also, Asians tend to eat more vegetables overall, compared to Americans, she says.
Further study is needed to determine if the cancer-fighting compounds behave differently depending on the amount and type of cruciferous vegetables eaten, Nechuta says.
There will be about 290,000 new cases of breast cancer in the U.S. in 2012, and nearly 40,000 women will die from the disease, according to the American Cancer Society.
These findings were presented at a medical conference. They should be considered preliminary, as they have not yet undergone the "peer review" process, in which outside experts scrutinize the data prior to publication in a medical journal.