The research on chia, thus far, shows that whilst it is great nutritionally (omega-3s, minerals, fibre, etc.) it isn't a miracle cure for anything. As long as you include a sensible amount in your diet (a tablespoon or two is fine) and eat a balanced and varied diet, then they certainly shouldn't do any harm. Unless you have an allergy...
Flax seeds will do a similar thing, and are cheaper and more widely available.
Both seeds are high in omega-3 fatty acids, fibre, protein and various antioxidant vitamins and minerals. Chia has a slightly better profile than flax.
Hope that helps!