One of the American Cancer Society’s key dietary recommendations to reduce the risk of cancer is to include cruciferous vegetables such as broccoli.
Sulforaphane is an isothiocyanate, an organic chemical compound that has been shown to inhibit the growth of carcinogen-induced cancer. Sulforaphane is found in cruciferous vegetables and is especially high in broccoli. Sulforaphane works by increasing the enzymes in your liver that destroy the cancer inducing chemicals you ingest in food or encounter in the environment
Sulforaphane has been found in laboratory studies to inhibit the growth of human breast cancer cells and stop the growth of human ovarian cancer cells. High intake of broccoli and other cruciferous vegetables is associated with reduced risk of aggressive prostate cancer, and with a decrease in gastrointestinal and bladder cancers. The protective effect of cruciferous vegetable consumption on lung cancer has also been suggested.
Overcooking broccoli and cruciferous vegetables will dramatically lower the amount of cancer protective phytochemicals. Researcher Elizabeth Jeffery has discovered how to maximize the cancer fighting power of broccoli. It involves heating broccoli just enough to eliminate a sulfur-grabbing protein, but not enough to stop the plant from releasing the important cancer fighting compound sulforaphane.
The chemistry for triggering the release of sulforaphane is tricky. Sulforaphane is linked to a sugar molecule through a sulfur bond. When the broccoli enzyme breaks off the sugar to release the sulforaphane, a sulfur-grabbing protein can remove the newly exposed sulfur on the sulforaphane and inactivate it.
“Instead of worrying about overcooking the broccoli and losing the enzyme that releases the sulforaphane, we focused on heating the broccoli just enough to destroy the sulfur-grabbing protein, but not enough to harm the enzyme that releases sulforaphane from the sugar,” said Jeffery.
“We learned that sulforaphane is maximized when broccoli has been heated 10 minutes at 140 degrees Fahrenheit,” said Jeffery. “For the consumer, who cannot readily hold the temperature as low as 140 degrees, that means the best way to prepare broccoli is to steam it lightly about 3 or 4 minutes, until the broccoli is tough-tender.”
“Although our gut bacteria may be able to release some of the sulforaphane, we don’t have the enzyme to release sulforaphane in our body tissues, so our best bet is to use the enzyme in the broccoli,” Jeffery said. “The enzyme in the broccoli does a really good job of breaking that bond. You can break it simply by chopping the broccoli.”