Cruciferous vegetables like broccoli are celebrated for their cancer-fighting properties, but improper cooking can severely reduce their benefits. The key enzyme responsible for converting compounds into anticancer substances, myrosinase, is highly sensitive to heat. Overcooking broccoli can cut its sulforaphane content by more than half.
Sulforaphane isn’t naturally present in its active form; it must be produced when myrosinase acts on its precursor compounds. Dr. Liao Zhiying, in a post on his Facebook page “Dr. Liao Zhiying – Proton Therapy / Cancer Supportive Medicine,” explained that if broccoli is placed directly into boiling water after cutting, the enzyme is inactivated before it can fully convert the compounds. As a result, even large amounts of broccoli may fail to deliver the expected anticancer benefits.
To preserve the maximum anticancer compounds, Dr. Liao recommends three steps. First, allow cut broccoli to sit for 40 minutes before cooking. This waiting period gives myrosinase time to act, producing more sulforaphane. Once transformed, these compounds become more heat-stable, so subsequent cooking causes less loss.
For cooking, he advises steaming broccoli over high heat for 3–5 minutes instead of boiling. Boiling can leach nutrients into the water, whereas steaming maintains both the vegetable’s crispness and its active compounds. “Eating for cancer prevention isn’t just about what you eat, but also how you eat it,” Dr. Liao emphasised.
For those who prefer softer textures, pairing broccoli with ingredients that boost enzyme activity—like a sprinkle of mustard powder or raw sesame leaves and grated white radish—can help compensate for the anticancer compounds lost during cooking.
