Cooking Veggies May Not Cut Nutrients

Dec. 21, 2007 -- Cooking vegetables may not reduce all of the nutrients in those veggies, according to a new Italian study.

The University of Parma's Nicoletta Pellegrini, PhD, and colleagues bought freshly harvested carrots, zucchini, and broccoli at a local market.

In their lab, the scientists measured levels of various antioxidants in the raw vegetables. Then they boiled, steamed, or fried the vegetables. Lastly, they measured antioxidant levels in the cooked vegetables.

Raw vegetables were loaded with antioxidants. After cooking, their antioxidant levels were a mixed bag.

In some cases, the veggies lost antioxidants to cooking. But not all antioxidants decreased when cooked -- and in some cases, certain antioxidant levels rose when cooked.

For instance, steamed broccoli contained higher levels than raw broccoli of glucosinolate compounds, which may reduce cancer risk. And boiled carrots contained higher levels than raw carrots of carotenoids, which give carrots their bright orange color.

No single method of cooking stood out as being best for all antioxidants.

"Our results suggest that for each vegetable a preferential cooking method could be selected to preserve or improve its nutritional qualities," write the researchers.

Their findings appear in the Journal of Agricultural and Food Chemistry.