In a finding that defies conventional culinary wisdom, researchers in Italy report that cooking vegetables can preserve or even boost their nutritional value in comparison to their raw counterparts, depending on the cooking method used.

Their study is scheduled for the Dec. 26 issue of ACS’ Journal of Agricultural and Food Chemistry, a bi-weekly publication.

Nicoletta Pellegrini and colleagues note that although many people maintain that eating raw vegetables is more nutritious than eating cooked ones, a small but growing number of studies suggest that cooking may actually increase the release of some nutrients. However, scientists are seeking more complete data on the nutritional properties of cooked vegetables, the researchers say.

In the new study, the researchers evaluated the effects of three commonly-used Italian cooking practices — boiling, steaming, and frying — on the nutritional content of carrots, zucchini and broccoli. Boiling and steaming maintained the antioxidant compounds of the vegetables, whereas frying caused a significantly higher loss of antioxidants in comparison to the water-based cooking methods, they say. For broccoli, steaming actually increased its content of glucosinolates, a group of plant compounds touted for their cancer-fighting abilities. The findings suggest that it may be possible to select a cooking method for each vegetable that can best preserve or improve its nutritional quality, the researchers say.