I'm a vegetarian, and I try to eat as many fresh veggies as possible, because Mom always told me that they lose all their nutritional value when they are cooked. But that may not be necessarily true.
The University of Parma's Nicoletta Pellegrini, PhD, and colleagues bought freshly harvested carrots, zucchini, and broccoli at a local market and tested the levels of various phytochemicals and antioxidants in them while they were raw. Then, they boiled, steamed or fried the veggies and measured them again.
Raw vegetables were, of course, loaded with antioxidants. After cooking the veggies lost antioxidants, but the story wasn't as bad as expected; not all antioxidants decreased when cooked. Certain antioxidant levels actually went higher. 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.
Their findings appear in the ACS publication, Journal of Agricultural and Food Chemistry. In another press release from the ACS (American Chemical Society), the organization discusses the effect of cooking peanuts, which is actually a bean and not a true nut. Many people in the southern states love to eat "boiled peanuts," which is a regional treat. Raw peanuts are boiled in a pot of hot, salted water to create this snack, and many people assume that the good substances in the peanuts are driven out by this process.
Now it appears that boiled peanuts might actually contain higher amounts of substances that can help prevent diseases than regular peanuts. Most of the peanuts we eat by the handful (or in peanut butter or candy bars) have been roasted in ovens. Dr. Lloyd Walker, a scientist from Alabama A&M University, discovered that boiling is a very healthy way to prepare peanuts.
His study, in the American Chemical Society’s Journal of Agricultural and Food Chemistry, found that boiled peanuts have four times as many healthy isoflavones as raw peanuts or roasted peanuts. These chemicals may help to keep people healthy and prevent dangerous illnesses, such as cancer, diabetes and heart disease.
It's interesting to note how cooking, heating and preparing cooked vegetables and peanuts doesn't necessarily kill off what is good about that food. It has been known for some time that tomatoes show the most lycopene, another healthy substance, only when they are cooked.