Health experts say depression treatment needs to change to incorporate healthy eating and are calling for the government to subsidise the cost of a dietitian for people with the debilitating mental condition.

Over the last decade, researchers have established a clear link between the quality of a person's diet and their risk for depression and anxiety.

The Deakin Food & Mood Centre's SMILES trial was the first to show dietary changes could be used as a treatment for clinical depression.

At the end of SMILES trial, a third of those to follow a Mediterranean-style diet were no longer considered clinically depressed.

A new study, published in journal BMC Public Health, has now shown dietary intervention is a cost-effective way to assist those with depression.

Researchers examined the costs of counselling, healthcare visits (or GP visits), medicine, food, travel and lost productivity, and compared this with the health care expenditure of participants of the SMILES trial.

Overall, healthcare costs were $856 lower over the 12 weeks of the trial.

Food costs alone for this group were estimated at $26 per week lower than what they would have otherwise been pre-trial.

The total burden to the healthcare system and society was $2591 lower.

Study co-author Dr Mary Lou Chatterton, a research fellow at Deakin Health Economics in the Centre for Population Health Research, said economic modelling indicated dietary intervention not only saved the person with depression money, but the whole of society too.

"What it showed was that when it came to the SMILES trial, those who received support to eat a Mediterranean-style diet had lower overall costs compared to the comparison group," Dr Chatterton said.

"The lower cost was partially due to fewer health professional visits, such as to doctors, dentists, and psychologists. The participants on the dietary intervention also reported less time lost from unpaid activities such as housework and childcare."

SMILES creator Professor Felice Jacka said mental health involved the whole body, and good diet is a key driver of health.

She said the role of a healthy diet - including the consumption of wholefoods, fruits and vegetables and wholegrains - held an important place in the treatment of depression, and patients should have cheaper access to dietitians.

"We have shown over and over again that a clinical dietitian, someone with that proper training, is by far the best person to achieve meaningful, lasting dietary change," Professor Jacka said.