Some nutrients are lost when broccoli is frozen. Often, however, freezing a vegetable can keep many of the nutrients in, and frozen vegetables are a good alternative to canned.
Frozen vegetables can be a superior choice when they are frozen at the peak of ripeness, when they have the most nutritional value. Fresh vegetables that are shipped are often picked before they are fully ripe to allow for travel time. As a result, they have not developed the full range of nutrients. When a vegetable is in season, it should be bought fresh. If it is not, frozen is the best option.