Ask HN: Is it good idea to take protein supplements in your diet?

Ask HN: Is it good idea to take protein supplements in your diet?
I've a lean body and I've been working out for more than a year. But I've not gained a much of mass and I cannot see much of a difference in my body. I have seen most of the people taking protein supplements and mass gainers everyday who work out. I've also heard some people saying taking supplements is going to have side effects on your body. I would like to know if taking protein supplements and mass gainers is a good idea without any side effects on my health either now / later in my life. If this is not a good idea, then what are the other ways to gain mass and gain muscles along with my everyday workout?