What’s the best way to cook vegetables? Steaming, study says

Steamed, boiled or stir-fried – how do you eat your vegetables? A new study suggests that the way you prepare broccoli and other veggies could the amount of cancer-fighting benefits on your plate. Ashley Fraser / The Ottawa Citizen

TORONTO – Steamed, boiled or stir-fried – how do you eat your vegetables? A new study says that the way you prepare broccoli and other veggies could take away from the amount of cancer-fighting benefits on your plate.

Your best bet is to steam broccoli, and only for three to four minutes until the vegetable turns a bright green, American researchers suggest.

Scientists from the University of Illinois say that vegetables – in this case they looked at broccoli – lose their nutritional value depending on how they’re cooked.

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Lead author Dr. Elizabeth Jeffery boiled, microwaved and steamed broccoli in her comparison.

Broccoli is packed with sulforaphane, a naturally-occurring plant compound that’s supposedly a cancer-fighting agent. But the compound is only activated with the help of an enzyme called myrosinase.

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According to Jeffery’s research, boiling and microwaving the vegetable, even for just a minute, broke down the myrosinase. But steaming broccoli for up to five minutes helps retain the important enzyme.

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“Past food processing has tended to focus on improving taste, visuals and microbiological safety,” Jeffery told the Daily Mail.

“Now our task is to go further. Processing can ensure that the bioactives – the cancer protective compounds – arrive in your digestive system in a form the body can use.”

But if you prefer your broccoli cooked longer via boiling or microwaving, Jeffery says that the cancer-fighting benefits of broccoli can also be activated if you eat it with raw foods that have myrosinase.

Other uncooked cruciferous vegetables along with mustard greens, radish, brussels sprouts and arugula contain myrosinase.

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This isn’t the first study to point to the importance of how vegetables are prepared. Health Day points to these examples in previous research:

  • Crushing or chopping garlic, and then waiting 10 to 15 minutes before exposing it to heat allows its inactive compounds to convert into the active, protective phytochemical known as allicin.
  • Cooking tomatoes and other foods that contain lycopene allows your body to more easily absorb the beneficial phytochemical.
  • Boiling vegetables for a long time means losing water-soluble vitamins, such as vitamin C, folate and niacin that leach into the water.

Jeffery’s findings were presented this weekend at the American Institute for Cancer Research meeting. There, other researchers also shared their work on processed meat and cancer risk, health risks tied to obesity, and a string of other health issues.

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