Broccoli is very rich in nutrition and very safe to eat vegetable because it has very less or no side effect to human heath. Broccoli is a very good source of dietary fiber, pantothenic acid, vitamin B6, vitamin E, manganese, phosphorus, choline, vitamin B1, vitamin A (in the form of carotenoids), potassium and copper. Broccoli is also a good source of vitamin B1, magnesium, omega-3 fatty acids, protein, zinc, calcium, iron, niacin and selenium.
But note that it is recommended to eat broccoli raw because cooking process destroys some of its antioxidants and nutrients.
Here I have found some of the benefits of broccoli in Pictures which I have taken from Doctor ASky Facebook