Moody foods: the link between poor diet and mood disorders

Unhealthy diets before and during a pregnancy could contribute to greater risk of perinatal depression and anxiety. 

With as many as one in five Australian women likely to experience depression and/or anxiety during pregnancy and postpartum, perinatal mood disorders are a common – if unwelcome – aspect of motherhood. 

But while there are many known risk factors associated with poor mental health, we don’t yet understand what makes the female brain so vulnerable to these conditions during pregnancy and after giving birth. 

Dr Luba Sominsky – a Paediatric Research Fellow at Deakin University – works within the field of neuroimmunology; the study of how the brain and the immune system interact. Her work indicates that poor diets before and during a pregnancy could interfere with the brain mechanisms that regulate our moods, leading to perinatal depression and anxiety later on.

Inflammation, a double edged sword

The human body is a fascinating, interconnected organism, with different systems communicating with each other to keep us alive. These systems also impact other areas of our health, like our moods and general mental state. 

Dr Sominsky says the immune system has a particular role to play here. When we get sick, our white blood cells fight back with a robust immune response. It’s very effective in killing off the infection, but if the exposure is prolonged it can also damage other parts of the body – like our brains. 

This can be exacerbated by our diets, especially when they’re high in saturated fats and sugar. When these foods are consumed over an extended period, our microglia – the major immune cells in our brains – respond to the nutrients in the same way they approach a pathogen. 

This isn’t always a bad thing. Generally, you want microglia to kick into gear so they can respond to infections or injury. But when this activation becomes chronic, the body can become diseased. 

 “Unlike in the case of a protective inflammatory response, which works to protect the body from invading pathogens, chronic inflammation is associated with a range of health issues, including mental health conditions.”   

The changing maternal brain 

According to Dr Sominsky’s research, poor diets can increase microglial activation and disrupt neurogenesis – the process of producing new brain cells – after a pregnancy. 

In her preclinical study with collaborators from RMIT University, ‘Maternal diet before and during pregnancy modulates microglial activation and neurogenesis in the postpartum rat brain’, she confirmed that when the subjects – pregnant rats – ate a diet high in fat and sugar, their microglial cells were more active, even after they’d given birth.  

She also found that while they were on this diet, pregnant rats had an increased rate of neurogenesis than normal. New brain cells were produced in the hippocampus, the area of the brain that deals with memories. Just like with activating microglial cells, this is usually a good thing; in an adult brain, new neurons can help to improve a person’s memory and their ability to learn. 

But according to previous research, neurogenesis is usually suppressed during pregnancy and in the early postpartum period after the mother has given birth. 

“This temporary suppression seems to be something the maternal brain needs to undergo in preparation for motherhood. So it’s possible that increased neurogenesis during the sensitive time of pregnancy and birth can affect maternal mood and other behavioural processes.” 

No substitute for a healthy diet

There are many factors that can lead to mood disorders and poor mental health, from the environment you live in, to your biological makeup. But as we’ve seen across Dr Sominsky’s research, our diets can play a role in regulating our immune systems and brain health. 

And if you’re part of a group at risk of developing a mood disorder – such as the one in five pregnant Australian women – it could be the preventative key we’re looking for. Perhaps we should be working with expectant mothers to improve their diets before and during their pregnancies? 

That’s what Dr Sominsky thought. She hypothesised that a diet high in omega-3 could be used to put mothers back on a healthy mental and physical track. These fatty acids are found in fish, nuts and plant oils, and have a range of benefits, from being powerfully anti-inflammatory – a big culprit at play here – as well as having neuroprotective and antioxidant effects. 

Several studies have shown the potential benefits of omega-3 for women suffering perinatal depression. But despite this, Dr Sominsky found that all was not as it seemed.  

“Surprisingly, we found that while diets with a high content of omega-3 fatty acids helped to reduce inflammation – triggered by the long-term consumption of high fat and sugar diets before pregnancy – it had similar negative effects on neurogenesis.”

In her study, Dr Sominsky found that the rat mothers who consumed lots of omega-3 during their pregnancies also had an increased number of newly formed neurons – similar to the rats whose diets were high in fat and sugar. 

These findings indicate the need for further research into what triggers chemical imbalances within the brain and emphasises the importance of a balanced diet for overall health. 

“Healthy and balanced diets during pregnancy are essential for the health of the expectant mother and the developing baby,” she says. “What’s equally important though is to increase the awareness of the impact our dietary choices can make throughout our life, whether it’s on our cardiovascular health, mental health or fertility – and whether you’re an expectant mother or not.”

Dr Sominsky will be continuing her research with a human birth cohort through Barwon Health, where she’ll be working to establish a set of blood biomarkers that will help to identify when pregnant women could benefit from early prevention strategies. 

Dr Luba Sominsky is a Paediatric Research Fellow at Deakin University. 

Curious? Check out her study: ‘Maternal diet before and during pregnancy modulates microglial activation and neurogenesis in the postpartum rat brain’. 

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