Australasian Science: Australia's authority on science since 1938

Junk Diet’s Role in Dementia

The hippocampus, which has a role in learning, memory and mental health, is smaller in older people with unhealthy diets.

“We’ve known for some time that components of diet, both healthy and unhealthy, have a rapid impact on aspects of the brain that affect hippocampal size and function,” said A/Prof Felice Jacka of Deakin University, “but up until now these studies have only been done in rats and mice. This is the first study to show that this also appears to be the case for humans.”

The researchers used magnetic resonance imaging to measure the size of hippocampi in Australian adults aged 60–64 years. They also measured the participants’ regular diets and took into account a range of other factors that could affect the hippocampus.

The results of the study, published in BMC Medicine, suggest that the left hippocampi is smaller in older adults who eat more unhealthy foods, such as sweet drinks, salty snacks and processed meat. In contrast, older adults who eat more nutrient-rich foods, such as vegetables, fruits and fish, have larger left hippocampi.

These relationships existed over and above other factors that may explain these associations, such as gender, levels of physical activity, smoking, education or depression itself.

The findings have relevance for both dementia and mental health. “This latest study sheds light on at least one of the pathways by which eating an unhealthy diet may influence the risk for dementia, cognitive decline and mental disorders such as depression and anxiety in older people,” Jacka said.

“However, it also points to the importance of diet for brain health in other age groups. As the hippocampus is critical to learning and memory throughout life, as well as being a key part of the brain involved in mental health, this study underscores the importance of good nutrition for children, adolescents and adults of all ages.”