Alpha Personnel Recruitment is the sole recruiting agency for Auckland District Health Board so if you are interested in working there, might be helpful to register with them. Does not mean you have a job interview straight away but at least your name will be considered when opportunity comes.
btw, not so good news, this government is more into frontline medical service. So nutrition type of health promotion service in public sector might not have enough funding for more vacancies. Suggestion would be for you to look for companies in private sector and keep an eye on their website vacancy page. Even starts cold call if needed.