Although many natural remedies are based more on intuition than science, a surprisingly rigorous set of studies from different research labs is finding that eating broccoli helps our bodies fight the effects of air pollution.
Scientists have isolated the compound thought to help the body remove pollutants like benzene and fight inflammation. The compound, sulforaphane, is in broccoli, cauliflower, and other vegetables.
Placebo-Controlled Studies Find Health Benefits
In one study, researchers from Johns Hopkins School of Medicine randomly assigned people to drink a broccoli sprout drink or a placebo drink for 12 weeks. The 291 participants were living in an industrial part of rural Qidong, Jiangsu.
Qidong residents breathe high levels of pollutants like benzene. But after drinking the broccoli sprout drink, people passed significantly more benzene out through their urine.
The findings span different labs and countries. Researchers in Milan randomly assigned smokers to eat a portion (250g) of steamed broccoli or a placebo diet for 10 days. On the days when they ate broccoli, the smokers had significantly lower levels inflammation markers in their blood. That inflammation is triggered by air pollution.
In another study, a team of researchers in California had participants breathe diesel exhaust equivalent to spending a day on the freeway in Los Angeles. Beforehand, researchers randomly assigned some participants to eat broccoli sprout extract equivalent to about 150 grams of broccoli. The bodies of people who had eaten broccoli extract experienced a much less severe inflammation reaction to the pollution, as measured by their white blood cell count.
A Checkered Past for Claims About Plants
Critical readers would be justified in being skeptical of claims behind natural cures for air pollution. I’ve written about people who make incredible claims about plants cleaning indoor air. In this domain, claims are large, and evidence is sparse.
For some, the motivation may be the general belief in natural cures. That’s the case with this popular TED talk, which claims that a few potted plants can produce spectacular reductions in lung symptoms.
For others, the allure may be money. That seems to be the case with the people behind this plant pot, which the makers claim reduces pollutants by 75%. The makers’ Kickstarter campaigned netted 106,000 Euros. They now sell the pot for about 80 Euros a piece.
Yet tests in real-world conditions have found little or no effects of plants. For example, Smart Air conducted real-world tests of the effect of plants on PM2.5 levels in a Beijing apartment and found no effect.
I’ve written about the tests of a team of citizen scientists who tested whether an army of plants could reduce formaldehyde levels in an office room. Surprisingly, formaldehyde levels went up during their test.
There are studies that find benefits of plants. Yet most of these studies took place in small sealed containers surrounded by growing lights. The famous NASA study tested plants in small plexiglass boxes (although there are exceptions). Those conditions are nothing like normal people’s homes.
The Evidence for Plants vs. Broccoli
A look at the data on natural solutions for pollution are weak. The contrast is especially stark if we compare the effect of plants to the overwhelming evidence for “unnatural” solutions like air purifiers, masks, and their effects on health.
Yet against this backdrop of skepticism, the scientific evidence for broccoli is surprisingly well established. The researchers of the study in China pointed out that broccoli sprouts offer “a frugal means” to reduce the health effects of air pollution. That’s critical at a time when companies are hawking $2,000 imported air purifiers.
Five Foods That Help Your Body Fight Air Pollution
So how can we add sulforaphane to our diet? A handful of any of these five foods will give a daily dose of this air-pollution-fighting compound.
1. Broccoli – simple and easy to find
2. Broccoli sprouts – harder to find, but contain 10 times or more sulforaphane than broccoli
3. Brussel sprouts
4. Red cabbage
Scientific Studies on Broccoli and Air Pollution
Thomas is an Associate Professor of Behavior Science at the University of Chicago Booth School of Business and the founder of Smart Air, a social enterprise to help people across the world breathe clean air without shelling out thousands of dollars for expensive purifiers.