The Super-Veggies: Cruciferous Vegetables
Cruciferous vegetables have it all: vitamins, fiber, and disease-fighting phytochemicals. Here's how to get more of them.
By Elaine Magee, MPH, RD
Reviewed by Louise Chang, MD
What do broccoli, cauliflower, Brussels sprouts, kale, cabbage, and bok choy have in common? They're all members of the cruciferous, or cabbage, family of vegetables. And they all contain phytochemicals, vitamins and minerals, and fiber that are important to your health (although some have more than others.)
In fact, health agencies recommend that we eat several servings per week of cruciferous vegetables -- and for good reason.
Lower Cancer Risk?
One of the big reasons to eat plenty of cruciferous vegetables is that they may help to lower your risk of getting cancer.
A review of research published in the October 1996 issue of the Journal of the American Dietetic Association showed that 70% or more of the studies found a link between cruciferous vegetables and protection against cancer.
Various components in cruciferous vegetables have been linked to lower cancer risks. Some have shown the ability to stop the growth of cancer cells for tumors in the breast, uterine lining (endometrium), lung, colon, liver, and cervix, according to the American Institute for Cancer Research. And studies that track the diets of people over time have found that diets high in cruciferous vegetables are linked to lower rates of prostate cancer.
Lab studies show that one of the phytochemicals found in cruciferous vegetables - sulforaphane - can stimulate enzymes in the body that detoxify carcinogens before they damage cells, says Matthew Wallig, DVM, PhD. Through different mechanisms, two other compounds found in cruciferous vegetables -- indole 3-carbinol and crambene -- are also suspected of activating detoxification enzymes.
Further, research suggests there is some important synergy between the various compounds in cruciferous vegetables. Wallig, professor of comparative pathology at the University of Illinois at Urbana-Champaign, discovered that crambene is more active when combined with indole 3-carbinol.
Another way cruciferous vegetables may help to protect against cancer is by reducing oxidative stress. Oxidative stress is the overload of harmful molecules called oxygen-free radicals, which are generated by the body. Reducing these free radicals may reduce the risk of colon, lung, prostate, breast, and other cancers.
In a study funded by the National Cancer Institute, 20 participants were encouraged to eat 1 to 2 cups of cruciferous vegetables a day. After three weeks, the amount of oxidative stress in their body was measured. Then, after a three-week wash-out period, the study participants were told to take a multivitamin with fiber. Again, the oxidative stress was measured three weeks later.
And the results? Oxidative stress in the subjects' bodies dropped 22% during the period when they were eating lots of cruciferous vegetables. But the change during the multivitamin segment was negligible (0.2%), says lead researcher Jay H. Fowke, PhD, an assistant professor and cancer epidemiologist for the Department of Medicine at Vanderbilt Medical Center in Nashville, Tenn.
More study is needed, but Fowke feels the evidence is pretty strong that eating cruciferous vegetables is a particularly healthful choice.
"There's no harm to it and consistently, across the line, it's associated with improved health and a reduced risk of various chronic diseases," he says in an email interview.
It's best, he says, to eat these veggies raw or only lightly steamed to retain the phytochemicals that make cruciferous vegetables special in terms of health.
Diets rich in fish and vegetables (including cruciferous and dark-yellow veggies) may also help to protect against cardiovascular disease. A recent study found that such a diet was linked to lower levels of markers of inflammation in the body. These markers may signal an increased risk of cardiovascular disease.
In another recent study, diets low in cruciferous and yellow vegetables, wine, and coffee but high in sugar-sweetened soft drinks, refined grains, and processed meat were identified as possibly increasing chronic inflammation and raising the risk of type 2 diabetes.
Comparison of Cruciferous Vegetables
Which cruciferous vegetables have the most vitamin A, vitamin C, and folic acid? The answers are: