Probiotics can help boost your immune system, especially if your gut flora has been compromised by use of antibiotics.
Be careful with "advice" from friends. I have lots of friends and colleagues who try to give me nutrition advice for Crohn's even though they no nothing about disease and their advice comes from a book or a magazine. (Some of them don't realize I have a nutrition degree). Don't completely discredit what they say, they obviously care, but make sure you do your own research and discuss with your doc or a dietician if you are unsure.