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Eating Broccoli May Give Harmful Chemicals The Boot

Researchers say eating broccoli sprouts could help protect against the harmful effects of air pollution.
Julie Gibbons/Flickr
Researchers say eating broccoli sprouts could help protect against the harmful effects of air pollution.

We get a little suspicious when we hear the claims that it's possible to get rid of the gunk that accumulates in our cells by doing a cleanse with "clean" foods.

But what if some foods actually do help detox the body?

The results of a recent clinical trial suggest that compounds in cruciferous vegetables like broccoli (and kale) prod cells to get rid of certain air pollutants. The intriguing randomized control trial of about 300 Chinese adults found that consuming a beverage made with broccoli sprouts every day for three months led to high rates of excretion (in urine) of two harmful chemicals: benzene and acrolein.

Now, benzene and acrolein are pretty common. If you're pumping gas at a gas station, you'll breathe in a little benzene, and if you're smoking or around smokers, you'll take in acrolein (and some benzene, too). If you live in a place with heavy pollution, you may get a big enough dose of benzene to make you sick — though that can be tough to prove.

Lately, scientists have been zeroing in on a compound called glucoraphanin that seems to have a protective effect against these and other toxins.

Animal model studies have shown that when vegetables containing glucoraphanin are chewed or swallowed, another compound called sulforaphane appears on the scene and kicks enzymes into action to take up pollutants and clear them from the body in urine. In other words, sulforaphane seems to act like fuel for the body's own trash collection and disposal services.

The new study, published online in early June in the journal Cancer Prevention Research, set out to figure out whether drinking a half-cup of a beverage containing broccoli sprouts would increase the rate of excretion of benzene and acrolein. (The researchers say they chose these chemicals because they were among the most stable molecules among pollutants to track.)

About half of the 291 Chinese adults in a rural farming community in Jiangsu province — a community with very high levels of air pollution — who participated in the study were given the broccoli sprout drink every day for 12 weeks, while the other half got pineapple and lime juice.

The researchers, who hail from Johns Hopkins University and several other institutions in the U.S. and China, found that among the people consuming the broccoli sprout beverage, the rate of excretion of benzene increased 61 percent throughout the 12-week period. As for the acrolein, the excretion rate went up 23 percent during the trial.

"We thought the pathway might respond initially, and then the [compounds] would wear out their welcome and the body would tune out," Thomas Kensler, a researcher at both Johns Hopkins and the University of Pittsburgh School of Medicine and an author of the study, tells The Salt. "But the effect was just as vigorous at the beginning as at the end, which suggests that over one's lifetime, you could enhance this preventative activity in the body [with food]."

While the researchers say they have no idea whether superfoods like broccoli can actually prevent cancer or other diseases, this new study lays some important groundwork that will make it easier to answer that question.

"The assumption is that if there's less carcinogen in the body, there's less risk," he says. "But at some point we need to do a definitive trial to find out if you take this approach for months or years whether [rates] of disease are dampened."

Kensler admits the study is "quirky." But he's optimistic that the benefits of consuming broccoli and its cousins may extend way beyond detoxicating the body of benzene and acrolein. "Almost for certain we think that other toxins will be influenced in similar ways," he says.

But here's a caveat: The sulforaphane is most likely to work on chemicals you've just been exposed to — not those that stick around in the body. The researchers don't know whether the compound has any effect on the chemicals stored in fat cells — things like pesticides, DDT or dioxin.

But Kensler says he's excited about what the findings could mean for combating the health effects of air pollution. The next step will be to figure out how little of a food like broccoli sprout you would need to eat and how often you'd need to eat it to get the protection.

They'll also have to figure out what to do about the fact that "not everybody loves broccoli."

Still, "we think these foods provide awesome opportunities, particularly because they're relatively inexpensive and culturally appropriate for most people," he says.

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