Like all other things, broccoli needs to be given to your guinea pig in moderation. This is because broccoli can cause your guinea pig to get an upset stomach, and give your guinea pig bad gas, and bloating.
When you give your guinea pig some broccoli, make sure it is washed well, and it is fresh. Do not give your guinea pig broccoli if it is old, and starting to go bad.
In moderation, given to your guinea pig in small amounts, no more than once per week, broccoli can be very healthy.
Just look at how much these guinea pigs are loving the broccoli they were given.