Older Australians WHO eat a diet high in ultra-processed foods have an increased risk of depression, new research has found.

The findings published in BMC Medicine found Australians aged 70 and older WHO eat at least four servings of ultra-processed food a day increased their risk of depression by 10%.

Ph.D. Candidate Belayneh Mengist Miteku from the Institute for Mental and Physical Health and Clinical Translation (IMPACT) in Deakin University's School of Medicine said the findings were an important reminder to older people to include as much freshly prepared whole food in their diets as possible.

"Depression in older Australians is a major problem and can lead to poor health outcomes and even premature death, so reducing depression risks is an important way to ensure people are living well into their older age," Miteku said.

"We know that older people might be tempted to look for tasty and convenient meals that don't require much preparation, but pre-prepared and frozen meals often include a lot of ultra-processed ingredients that might be tasty but are not healthy when eaten too often. Cost and convenience, as well as concerns around food that is crunchy, tough-to-chew or difficult to swallow, are the main issues."

"Ultra-processed foods are not just limited to junk and fast foods, like chips, hamburgers and soft drinks. They also include mass-produced and highly refined products that might be considered relatively healthy, like diet soft drinks, some fruit juices and flavoured yoghurts, margarine, and many ready-to-heat frozen meals and packet-based meal flavourings."

Ultra-processed foods also include processed meats, such as bacon, ham, corned beef and salami, sweet biscuits and cakes, chocolate and lollies, meat pies and sausage rolls, ice cream, many breakfast cereals, mass-produced packaged bread, soy or other non-dairy milk, malt drinks, cordial and supplement drinks such as Ensure and Sustagen.

Miteku said the study used a large sample of more than 11,000 older adults living in the community and was significant as it focused on the importance of mental health hygiene in older adults and provided credible evidence towards healthy ageing.

Participants WHO consumed four servings of ultra-processed food a day were compared to participants WHO ate less than four servings of ultra-processed food a day, and both groups were screened for depressive symptoms.

IMPACT's Associate Professor Mohammadreza Mohebbi said the findings were further evidence of the need for policy change and improvements to dietary guidelines to reduce the growing reliance on ultra-processed food in the Australian diet.

"We know reducing ultra-processed food has a positive impact on our physical health, and this research is further evidence that reducing ultra-processed food in our diet will contribute to better mental health and quality of life," Associate Professor Mohebbi said.

"These findings will also provide much-needed evidence for health care professionals to incorporate dietary recommendations into mental health care for ageing populations."