Diet may influence risk of depression and Alzheimer’s disease

New research from Edith Cowan University (ECU) has shown that diet could influence the risk of both depression and Alzheimer’s disease (AD). Evidence suggests that depressive symptoms are both a risk factor for AD and a reaction to early memory problems.

ECU Researcher Dr. Samantha Gardener noted that healthy dietary patterns potentially attenuate some of the negative impact that depressive symptoms have on AD-related blood-based biomarker alterations. These biomarkers are biological molecules found in blood that can be measured and used to track progression of the disease.

The findings, now published in the journal Neurobiology of Aging, provide insightful contributions to the understanding of the interactions between diet, depressive symptoms, and AD-related blood-based biomarkers.

“Nutritional factors can impact brain health through inflammation, oxidative stress, vascular function, neuroplasticity, and via the gut-brain axis. These biological pathways may influence neurotransmitter systems and neuronal function, ultimately affecting mood and cognition,” she said.

The Mediterranean diet, which consists of an abundance of plant foods, olive oil, whole grains, and a moderate intake of red wine, has been inversely related to stroke, depression, cognitive impairment, and AD. In comparison, a typically Western diet, which consists of higher amounts of processed foods and sugars could result in an increased decline in certain brain functions.

“The Mediterranean diet is full of antioxidants and flavonoids and a lot of other really interesting compounds that reduce inflammation and oxidative stress in the brain, along with healthy fatty acids which are crucial for learning and memory,” Dr. Gardener said.

“It is crucial to note that while observational studies provide valuable insights, randomized controlled trials investigating the effects of specific dietary interventions on depression and dementia due to AD are needed. Such trials can provide more definitive evidence on the potential benefits of targeted dietary interventions in managing these conditions.”

Alzheimer’s disease is estimated to affect around 50 million people world-wide, and is expected to increase to 152 million by 2050. The annual costs associated with the disease and other dementia-related conditions is estimated at $909 billion annually, or around 1% of the global gross domestic product.

In Australia, an estimated $3.7 billion is spent annually on the diagnosis, treatment and care of individuals with dementia.

ECU Ph.D. student Hilal Salim Said Suliman Al Shamsi noted that among individuals diagnosed with AD, depression occurs in about 50%.

“A longitudinal analysis showed that 40% of older adults with a diagnosis of depression progressed to AD over a relatively short median follow-up period of 27 months. The same analysis found that the risk of progression to AD was significantly higher among patients who had an active history of depression over the previous two years than among those with a more remote history of depression,” he said.

To date, there are no known specific curative measures for AD, but Dr. Gardener said that delaying onset may reduce disease prevalence and its public health burden.

“Research identified 14 modifiable risk factors that are proposed to account for around 45% of dementia cases worldwide. Of these 14 modifiable risk factors, five can be positively impacted by a healthy diet, including hypertension, obesity, alcohol intake and depression.

“Other modifiable risk factors include physical activity and sufficient sleep. If we can address all these things, nearly 45% of dementia cases can theoretically be prevented.”