Whether you consult a registered dietitian or a registered nutritionist will depend on the kind of advice you want.
A dietitian is a qualified health professional, who as well as providing general health advice, can also work with people with special dietary needs due to health conditions such as coeliac disease.
A nutritionist should be able to provide information about food and healthy eating, but not about special diets for medical conditions.
Nutritionists
The title of nutritionists isn’t protected by law, meaning that anyone can advertise their services as a nutritionist. So it’s important to find a nutritionist who is appropriately qualified and registered by a trustworthy professional body.