The evidence grows that ultra-processed foods play a role in depression

Ready to eat foods: So convenient, so tasty, and maybe so not good for your heart or mental health.

Ready to eat foods: So convenient, so tasty, and maybe so not good for your heart or mental health. Photo: Getty

There’s a party in your pantry that’s waiting to happen. Think of those packets of biscuits, sugary cereals, crackers and chips – and those salamis on a string! – tucked away in a dark corner for some months.

And what about those frozen hot dogs, pizzas and sausage rolls that have been in the bottom of the freezer since Christmas?

No worries. They’ll all be as tasty and more-ish and “fresh” as ever. Yay.

As will the fizzy drinks be fizzy. Because that’s how they’ve been designed – to last until you need them. Woo hoo! Party time!!!

But the party has a hang-over

This week, yet another study has found a link between eating ultra-processed foods – energy-dense, palatable, and ready-to-eat – and an increased risk of depression.

In particular, the researchers – Massachusetts General Hospital and Harvard Medical School – found that artificial sweeteners were implicated in the development of depression, or depressive behaviours, in women.

The study investigated the eating habits and mental health of more than 31,000 women aged between 42 and 62.

The participants were enrolled in the Nurses’ Health Study II – and the investigation ran from 2003 to 2017. Their diet was assessed every four years with ‘validated food frequency questionnaires’.

The women were free of depression at baseline.

The results

One disturbing thing became clear over time.

Participants who consumed high amounts of ultra-processed foods tended to have unhealthy habits and problems away from the dinner table.

Notably, they had greater BMI (body size), higher smoking rates, and increased prevalence of comorbidities like diabetes, hypertension, and dyslipidemia (an imbalance of fats, such as cholesterol) and were less likely to exercise regularly.

What about depression?

The study looked at two definitions of depression. One was a strict definition requiring clinically-diagnosed depression and regular use of antidepressants.

The second was a broader definition that included a clinical diagnosis and/or antidepressant use.

After adjusting for factors like age, exercise habits, and income, those with the highest consumption of ultra-processed foods had an increased risk of depression by both definitions.

Bottom line: the paper found that women who ate the highest level of ultra-processed food had a 50 percent higher risk of developing depression compared with those women that ate the least amount.

How might these foods cause depression?

It’s a bit vague at this point.

The researchers says that although the mechanism that associates ultra-processed foods (UPF) to depression is unknown, their findings suggest “artificial sweeteners and artificially sweetened beverages could be, as previous research has suggested, eliciting certain changes in the brain that are associated with the development of depression”

It’s still early days. However, there are some strong clues.

In August, researchers from the Girona Biomedical Research Institute  in Barcelona, also found that UPF consumption is associated with depressive symptoms.

But they also found brain shrinkage within the mesocorticolimbic brain network implicated in reward processes and conflict monitoring – which suggests compulsive eating for the fun of it. Followed by a come-down.

In 2021, we reported that it only takes four weeks for a diet of highly processed food to inflame the brain and elicit behavioural signs of memory loss.

This was a study done with older rats. The focus was on how a poor diet impacts ageing brain tissue and functioning. Research has shown that rat and human brains are remarkably similar in structure and function.

Another curious finding: the poor diet left the rats vulnerable to a threat, because they didn’t recognise the danger. They may have been blissed out by the fats, sugars, salts and mysterious preservatives. And eventually they paid the price.

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