for broccoli, taken from Dr. Weil's tip of the day:

Broccoli: Get the Most Bang for Your Buck
Want to preserve the cancer-fighting antioxidants broccoli contains? The best way to make sure you don't lose these natural health-promoting compounds is to steam fresh broccoli, rather than using other cooking methods.

Results of a study published in the Oct. 15, 2003, online issue of the Journal of the Science of Food and Agriculture showed that microwaving virtually strips broccoli of its major antioxidants, reducing them by up to 97 percent. The study was conducted by scientists working for the Spanish government.

Earlier studies had indicated that boiling was the cooking method most likely to deplete vegetables of their nutrients. In this study, boiling removed 66 percent of antioxidants from fresh broccoli; pressure cooking leached out 47 percent; and steaming had only minimal effects on antioxidant content.

Findings from a Finnish study published in the same issue showed that blanching vegetables before freezing eliminates up to one-third of their antioxidant content.