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Turns out, a serving of broccoli a day might actually keep the doctor away.

Carolyn Williams, PhD, RD
November 05, 2018

We’ve all heard the saying “an apple a day keeps the doctor away”, but a better idea might be eating some broccoli with that apple! There’s compelling research to suggest that eating cruciferous vegetables most days may reduce risk of certain cancers, thanks to compounds only found in those veggies.

What Are Cruciferous Vegetables, and Why Are They Special?   

The name “cruciferous” comes from the cross-shaped pattern that each vegetable’s flowers bloom. Broccoli, cabbage, kale, and cauliflower are cruciferous veggies you’re probably already familiar with, but there are also over twenty others that can usually be found in most grocery stores. While all vegetables are rich in their own assortment of nutrients and disease-fighting compounds, cruciferous vegetable are unique from other produce in that they also contain sulfur-based compounds called glucosinolates.

Glucosinolates are responsible for the slight odor when cooking broccoli or the bitter taste in turnip greens, but they also form biologically active compounds when broken down during digestion or cooking. These compounds (isothiocyanates and indoles are two) are associated with a reduced risk of cancer, as well as other diseases. In fact, researchers have been studying their effects for over 60 years, and several of them made the National Cancer Institute's list of the 40 most promising cancer-preventing agents.

Studies have also demonstrated that those broken-down compounds from glucosinolates have the potential to prevent the mutation of healthy cells into cancer cells; inhibit enzymes needed for the growth and metastasis of cancer cells; kill both benign and malignant cancer cells; detoxify or inactivate carcinogens that enter the body; provide anti-inflammatory, anti-bacterial, and anti-viral effects to reduce initiation of cancer cell; and alter hormone metabolism to decrease risk of hormone-sensitive cancers such as breast cancer.

Cruciferous Vegetables and Cancer

It's hard to prove that any food group (like cruciferous vegetables) has a role in cancer prevention, and here’s why: A clinical study would consist of subjects eating broccoli and Brussels sprouts for years, waiting to see when—or if—they get cancer during their lifespan. Not only would this take years, but other lifestyle factors like omega-3 consumption and physical activity would have to be ruled out as impacting the outcomes too, making the whole process of “proving” close to impossible.

Instead, researchers are forced to look for associations in a lab setting or within large population studies which means that the precise relationship between cruciferous vegetables and cancer is not clear. However, research suggests some pretty strong associations between cruciferous intake and cancer. In fact, most researchers agree that a higher intake of cruciferous vegetables is associated with a decreased cancer risk, with the strongest connections seen between cruciferous vegetables and lung cancer (in non-smokers) and colorectal cancer.

While genetics appear to play a role in the level of protection the compounds may offer each person, eating more cruciferous veggies can possibly reduce your risk for breast, stomach, prostate, and bladder cancers. The impact of these vegetables is also being studied in relation to brain-deteriorating diseases, heart disease, type 2 diabetes, and other inflammatory-related diseases.

How Much Should You Eat?

The Dietary Guidelines advise adults to eat between 2 to 2 ½ cups of vegetables daily and to consume a variety of vegetables from the five subgroups over a week. Cruciferous vegetables are categorized in either the “dark green” or “other vegetable” subgroup, but there’s no specific amount set for cruciferous vegetable intake. However, several of the cancer-related research studies suggest getting at least 5 servings in per week, or even better, a daily cruciferous vegetable serving.

The bottom line? Consume adequate fruit and vegetable intake each day for overall disease prevention. If you can make sure one of those daily servings is a cruciferous vegetable, then you might even reap additional health benefits—including extra cancer protection.

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