At present, the nutritionist's certificate can basically be used, and the so-called authority is not authoritative. Authority should not be manifested in certificates, but in people.
You can consider studying health managers, nutrition hygienists, public dietitians and internationally registered dietitians.
If you are from the health system, so is a nutritionist, but it was awarded by china health care association.
Landlord, in fact, you can call directly to ask where the certificate is. I don't know if it's from the Health Education Association or the Ministry of Health.