Way over saturated if you ask me. try to find a sub category that has less competition. its what i like to call getting in the back door... I have been real successful with this method. Instead of say just going for cancer, try like cancer rehab or something to go after... Bad example but you follow? Thx!
I have health niche blogs and squidoo lens. Both pointing health products and earn from affliate. I think if you monetize through pay per sale program it will be better than just using for adsense. There are lots of products paying you lots of commission!
I think this is good niche but it already has a lot of competition in terms of search engine traffic. So, it would be a bit difficult for you to drive organic traffic. Otherwise, if you can think of any other traffic source, it will be great.
Concentrate on its Bookmarking and link building and update is daily in start after that look for the competitors and do its On and Off SEO , Its a process you can get huge $$$ in start , Adsense market is long term but its bit slow but with your mind you Can make it Fast. Health niches are good so you Can take Good advantage from it as Well Saad