According to Health Day News, getting the necessary nutrients from vegetables may be even harder than you thought. New research shows that different ways of preparing, storing and processing vegetables can affect how good they are for you.

Broccoli, for instance, can lose as much as 97 percent of some antioxidants, or cancer-fighting compounds, when it is zapped in the microwave. Plus, vegetables that are blanched before freezing (a common processing technique) can lose up to one third of their antioxidants. Frozen storage can also cause losses, albeit much smaller ones.

Antioxidants are plentiful in vegetables and work to eliminate free radicals, which can damage cell DNA and contribute to various diseases. That’s why eating fiber, fruits, and vegetables, all of which contain antioxidants, can help prevent cancer and cardiovascular disease.

As it turns out, though, that protective effect is most pronounced when the vegetable is in its natural state.