Boiling vegetables diminishes anti-cancer properties.  

Science Daily (5/16) reports,

Researchers at the University of Warwick have found that the standard British cooking habit of boiling vegetables severely damages the anticancer properties of many Brassica vegetables such as broccoli, Brussel sprouts, cauliflower and green cabbage." Researchers from the Warwick Medical School at the University of Warwick found that after boiling "Brassica vegetables...from a local store, the "loss of total glucosinolate content after boiling for 30 minutes was: broccoli 77%, Brussel sprouts 58%, cauliflower 75% and green cabbage 65%." Glucosinolates are a key factor in cancer prevention, because they are "metabolized to cancer preventive substances known as isothiocyanates." Study author Paul Thornalley of the Warwick Medical School said, "If you want to get the maximum benefit from your vegetables...you need to consider stir frying steaming or micro-waving them."