Unhealthy Diets & Junk Food’s Effects On Your Brain

Deakin University and the Australian National University (ANU) have released a study showing that eating junk food can literally shrink your brain as it grows your waistline. This has been linked to mental health disorders such as dementia, depression, and attention deficit disorder. Healthy eating can, by contrast, prevent and help to treat these disorders.

Unhealthy diets can damage the brain

The researchers took account of other lifestyle factors that could limit the brain’s capacity, such as smoking, lack of exercise, depression, or low levels of education, and controlled for the differences between genders. They found that unhealthy eating could damage the brain all on its own, without any help at all.

The study found that the part of the brain used for learning, memory, and mental health (the left hippocampus) was significantly smaller in people who had unhealthy diets. Such people often drank sweet drinks and ate salty snacks and processed meats, consuming lots of saturated fats and refined carbohydrates. By contrast, people who ate healthier, nutrient-rich diets – with plenty of vegetables, fruits, whole grains and fish – had larger left hippocampi.

Researchers took MRI scans of the brains of Australians aged 60-64 years, monitored their current regular diet, and surveyed them in ANU’s PATH longitudinal study of ageing. The sample of 2,551 Australians who agreed to participate was chosen at random from appropriately aged Australians listed on the compulsory election roll.

This is the first time the research has been conducted with humans, and the results confirm what was seen in previous studies with rats and mice. (We wonder what the rodents would have had to say in the survey.)

Healthy diets can be used to treat mental illness

Previous studies showed that a poor diet is a risk major factor for developing mental illnesses such as depression and dementia. This is the first study to prove that diet could in fact be a cause of mental illness or be used to improve mental health. A healthy diet has been shown to treat depression and slow the effects of dementia.

Associate Professor Felice Jacka, lead author of the study and researcher at Deakin IMPACT Strategic Research Centre, said mental health problems are rising along with obesity. “Mental disorders account for the leading cause of disability worldwide, while rates of dementia are increasing as the population ages.”

Professor Jacka added that young Australians should be improving their diets now to protect the present and future health of their brain. “It points to the importance of diet for brain health in younger age groups. As the hippocampus is critical to learning and memory throughout life, this study underscores the importance of good nutrition for children, adolescents and adults of all ages.”

Professor Jacka has also studied pregnant women and found that those who ate processed foods during pregnancy were more likely to give birth to children with behavioural problems such as anger and throwing temper tantrums. These behavioural problems in children can be the warning signs of future mental health issues.

But why is unhealthy food bad for your brain?

Deakin University researchers stress that we shouldn’t single out any one nutrient as a “cure-all” for mental illness because overdosing on one nutrient cannot compensate for not getting a balanced diet of the others.

However, we can point to a few nutrients in healthy diets that can promote or damage brain health.

Diets high in fish are high in Omega-3 fatty acids, which reduce inflammation in the body and the brain. This is important because inflammation in the brain is one of the leading causes of dementia and other forms of brain damage.

Diets high in “good” carbohydrates such as vegetables, fruits, and wholegrains produce the steady flow of glucose that the brain needs to function. Diets high in refined carbohydrates or processed sugar, on the other hand, can damage your brain because they cause a spike in blood sugar followed by a crash as the body floods with insulin.

Did you know?

The name hippocampus is Latin for seahorse – because the hippocampus looks a bit like a seahorse. Humans have two hippocampi (not hippocampuses), one on the left side of the brain and one on the right.

The hippocampi are the parts of the brain associated with learning and memory, hence the connection to dementia. It is also connected to mood regulation, and you can see changes in the hippocampus when a person is depressed.

How can I eat healthier?

For information about how you can eat a healthy diet at different life stages, you can visit the following websites:

For more information about the results of the study, read the paper published in the BMC Medicine medical journal.

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