How Your Diet Affects Your Mental Health

Over the last half century, the global food industry has profoundly changed the way we eat. While we understand how these dietary changes have impacted physical health, their effect on mental well-being is only now being realised.

Eating picture from Shutterstock

Big business has successfully developed and marketed food products that appeal to our evolutionary preferences and have addictive properties.

Highly-processed snack and takeaway food products, rich in tasty fat and sugar, have now displaced much of the fruit, vegetables and other nutritious, unprocessed foods in our diets.

Largely as a result of these changes, there has been a staggering increase in the proportion of overweight and obese people across many countries. Common non-infectious illnesses, many driven by poor diets, are now the leading cause of death worldwide.

And we're now realising that unhealthy diets may also be contributing to poor mental health.

Diet and mental health

In Australia, as elsewhere, nearly half of the population will experience a mental health problem at some point in their lives. This means even people who are not personally affected are likely to know someone who has experienced such an illness.

Research now suggests that depression and dementia are affected by the quality of our diets across the life course.

Indeed, studies from countries as diverse as Norway, Spain, Japan, China, the United Kingdom, the United States and Australia show people whose diets are healthier are less likely to experience depression.

Research also shows that people who eat more unhealthy and junk foods are at increased risk of depression. This seems to also be the case in adolescents.

The most recent evidence points to the importance of mothers' diets for the physical and mental health of their children.

Although both diet and depression are influenced by a wide range of factors including income and education, these variables don't seem to fully explain the relationships.

And even though depression tends to change people's appetites and dietary choices at the time of illness, this doesn't appear to explain the long-term relationships between diet and depression either.

Diet and dementia risk

We now know that high cholesterol, hypertension, type 2 diabetes, elevated blood sugar and high BMI are all risk factors for dementia. And these are clearly influenced by dietary habits.

On the other hand, healthy dietary patterns, such as the Mediterranean diet, seem to protect against dementia and cognitive decline. Indeed, a recent European randomised trial showed people who adopted a Mediterranean-style diet as part of the study experienced better cognition than those in the control condition.

And although the study wasn't designed to assess depression risk, there was also a suggestion it was reduced for people who adopted the Mediterranean diet.

Taken together, this evidence suggests changes in global dietary habits may be influencing rates of depression and dementia. Importantly, given detrimental changes to diet are particularly obvious in younger people, the impact on the burden of these mental disorders may not yet be fully manifest.

It's becoming clear that common physical and mental illnesses co-occur and are likely mutually reinforcing. Obesity increases the risk for depression and dementia, while depression prompts obesity.

Heart disease is associated with depression, while worse outcomes face those with heart disease if they're also depressed. Risk factors for heart disease are also risk factors for dementia.

In this sense, the mind-body dichotomy that has informed much of psychiatric practice throughout history is beginning to appear artificial and redundant.

What all this means for general well-being is that measures to improve physical health should have positive benefits for the prevention and treatment of mental disorders. It also reinforces the need for governments and policy makers to urgently address our "obesogenic" food environment, which encourages people to eat bad food and remain sedentary.

And that means tackling the activities and predominance of the food industry.The Conversation

She has received Grant/Research support from the Brain and Behaviour Research Institute, the National Health and Medical Research Council (NHMRC), Australian Rotary Health, the Ian Potter Foundation, Eli Lilly, the Australian Meat and Livestock Board and The University of Melbourne, and has been a paid speaker for Sanofi-Synthelabo, Janssen Cilag, Servier, Pfizer, Health Ed, Network Nutrition, Angelini Farmaceutica, and Eli Lilly. She is president of the International Society for Nutritional Psychiatry Research (ISNPR) and the Alliance for the Prevention of Mental Disorders (APMD).

Felice Jacka is a Principal Research Fellow at Deakin University. This article was originally published on The Conversation. Read the original article.


Comments

    I have personally just finished up a deficit diet that lasted several months, and I can attest that the most important thing is balance... I have visible abs for the first time in my entire life, but I have to say, the mental drain of calorie counting every last thing that went into my mouth, or the guilt that went with eating anything unhealthy was incredibly difficult in itself...

    My point is, I was more miserable being overly healthy than not, so try and find a place in between.

      I highly agree with this. I found the more I wanted to cut to get abs (don't have them yet) the more my mental health/memory seemed to decline and the unhappier i got. Point is, change your goals every now and then and don't cement your self into one way of life, ie cutting or bulking, etc. I became very obsessed with loosing weight and cheat meals made me feel depressed.

    A fine example of how capitalism sometimes does not benefit society as a whole, just produces a whole lot of fat, unhealthy and depressed people. We are bombarded with messages of what to eat every day, without even knowing it.

      So if you don't even know it.
      How do you justify claiming to know it? O_o

      My point is that your comment is internally inconsistent.

      My favourite example of this is hard-solipsism.
      "Because the world may not be as it appears we can't justify knowledge claims."
      "You do realise that's a knowledge claim?"

    "Highly-processed snack and takeaway food products, rich in tasty fat and sugar, have now displaced much of the fruit, vegetables and other nutritious, unprocessed foods in our diets."

    Such generalisation, many sweeping. Wow.

    Seriously, how hard is it to have a crisper bin full of vegetables, a freezer full of meat, and a few recipe books on the shelf?

      Agreed, but let's not forget that the meat industry use all sorts of unnatural techniques to fill your freezer. Where I come from it's been suggested the high consumption of meat is responsible for high bowel cancer rates, not to mention other cancers. Meat is perhaps just another modern food processing fad. I guess you'd have to rear and slaughter the animals yourself to be sure it's as healthy as possible. Let's not even start on growing your own veggies. :)

    Did you spot those sponsor names? Let's not forget that it is in the best interests of some of these companies/institutions to promote any research that might sell more anti-depressants, anxiolytics and so on. I would recommend consulting other meta-analyses before forming any opinions this article may foster. Even though it may seem to be suggesting diet alone as a means to avoid the pitfalls of mental health problems, the disorders themselves are "advertised". That alone almost always leads to increased drug sales. That's often the primary goal of this kind of research sponsored by drug companies in particular. It's well documented.

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