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The Connection Between Diet and Mental Health

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Here’s a saying you’ve heard a thousand times:

“You are what you eat.”

You’ve heard it a thousand times because it makes perfect logical sense. If you want a healthy body, it stands to reason you need to consume healthy food. No one disputes that. Decades of research confirm it, as well.

A consistent diet that’s easy on the sugar and fat, high in fruits and vegetables, and includes lean protein choices such as chicken, fish – or plant-derived protein for vegetarians or vegans – can improve physical wellbeing across almost every major measure of health we have.

From cardiovascular health to muscle strength to bone density to endocrine function to immune response, a healthy diet helps ensure that your body functions at its best in the present and helps prevent the onset of chronic disease and common illness in the future.

That’s one reason there’s a multibillion-dollar diet and weight loss industry – worth seventy-two billion in 2019, according the Associated Press (AP) – in the U.S.

Another reason is the increase in obesity rates in the general population over the past 30 years – but that’s a different topic for a different article.

The diet industry exists because people know they need to eat well to be healthy: that’s true whether people are thin, overweight, or, like most of us, somewhere in between.

Here’s another saying you may or may not be familiar with:

“Food affects mood.”

That one sounds right, too – because we all understand what it means through experience. I’m not talking big picture, right now, though. I’m saying we all know this because we have experiences like feeling great after a huge, delicious meal. We also all have experiences feeling – well, yucky – an hour after eating a drive-thru combo meal (it happens to the best of us), or feeling edgy after consuming too much caffeine.

That much is obvious.

But it leads us to an important question:

“If food affects mood – in the short-term – then does diet

 have an impact on overall mental health?”

Spoiler alert: the research says yes, it absolutely does.

New Study Links Sugar Intake and Depression

Before I talk about the most recent research on the relationship between diet and mental health, I need to take a moment to talk about the research that’s been out there for a few years already. It’s important to know the new data didn’t materialize out of thin air. It’s built on the hard work of scientists going back years, but I won’t go back too far to make my point.

I’ll take you on a little time-travel survey of the best available data on the subject since 2010.


Here we go.

Study 1: The Mediterranean Diet (2013)

First, let’s look at research on The Mediterranean Diet, which received a lot of attention in the national media about five years ago, and for good reason. In the paper “Mediterranean Diet, Stroke, Cognitive Impairment, and Depression: A Meta-analysis” researchers found that people who adhere to a Mediterranean-style diet showed reduced risk of:

  • Stroke
  • Depression
  • Cognitive impairment
  • Dementia
  • Alzheimer’s disease

That’s important data because it draws a clear line not only from a specific diet to positive physical health outcomes, but also from a specific diet to positive mental health outcomes. However, that meta-analysis focused mostly on older individuals.

Study 2: Health Eating and Mental Health in Children and Adolescents (2014)

Now – to do our due diligence, and triangulate our data, as it were – let’s take a look at the research on the relationship between diet and mental health in younger individuals. This paper – “The Relationship Between Diet and Mental Health in Children and Adolescents: A Systematic Review” – confirms the positive impact of diet on mental health.

In their review of the available literature, researchers found that children and adolescents with poor dietary habits showed:

  • Higher incidents of mental health problems:
    • Depression
    • Anxiety
  • Higher incidents of behavioral issues:
    • Attention
    • Hyperactivity

In addition, researchers found that children and adolescents with good dietary habits showed the opposite:

  • Reduced odds of depression
  • Reduced odds of anxiety

I’ll get to that new study on sugar and depression, I promise: we’re almost done with our little research time-travel excursion.

Study 3: Fish, Fruits, Vegetables, and Whole Grains vs. Red Meat, Processed Foods, High-Fat Foods, and Sweets (2017)

Next up is a study conducted in China – Dietary Patterns and Depression Risk: A Meta-analysis –  that compared the impact of two types of diet on mental health. Here’s what they found:

  1. A dietary pattern that included high intake of fruit, vegetables, whole grain, fish, olive oil, low-fat dairy, and low intake of animal food was associated with a decreased risk of depression.
  2. A dietary pattern that included high intake of red and/or processed meat, refined grains, sweets, high-fat dairy products, butter, potatoes and high-fat gravy, and low intakes of fruits and vegetables was associated with an increased risk of depression.

That evidence needs no real interpretation: a healthy diet may decrease risk of depression, while an unhealthy diet may increase risk of depression.

Study 4: Diet Intervention and Depressive Symptoms (2019)

Okay. I’m done with the time traveling, and ready to land with you in the here and now: what does the most up-to-date research tell us about the relationship between diet and mental health?

It confirms all the previous data, then takes it one step further. Up to this point, the studies I’ve discussed have not studied cause and effect – they’ve identified associations and correlations. That’s why I used – and the study authors wrote – phrases like “increased risk of” and “higher instances of” rather than phrases like “caused an increase” or “resulted in a decrease.”

This study – A Brief Diet Intervention Can Reduce Symptoms of Depression in Young Adults: A Randomized Control Trial – is different. The goals of the study were to investigate:

  1. Whether young adults with depressive symptoms would comply with a three-week dietary intervention
  2. Whether this intervention can improve symptoms of depression
  3. Whether compliance with the diet would improve depressive symptoms

Can you see the difference?

The step further means this study does attempt to determine cause and effect: does improved diet result in decreased depression? Diet is the cause under observation, while a reduction in depressive symptoms is the effect they’re looking for.

To achieve their goals, researchers recruited 101 people with depressive symptoms and gave them all questionnaires designed to assess their current levels of depression and anxiety. They then divided the participants into two groups – the diet intervention group and the habitual diet control group. The habitual diet control group received no special instruction with regards to diet: they were simply told to eat as usual and come back after three weeks to repeat the depression/anxiety assessments.

The diet intervention group, however, was given specific instruction on what to eat for three weeks. Their diet – which was basically modeled on the Mediterranean Diet mentioned above – consisted of:

  • Vegetables: 5 servings per day
  • Fruit: 2-3 servings per day
  • Whole grain cereals: 3 servings per day
  • Lean protein (lean meat, poultry, eggs, tofu, beans): 3 servings per day
  • Unsweetened dairy: 3 servings per day
  • Fish: 3 servings per week
  • Nuts and seeds: 3 tablespoons per day
  • Olive Oil: 3 servings per day
  • Spices (turmeric and cinnamon): 1 teaspoon most days

They were also instructed to decrease their intake of:

  • Refined carbohydrates:
  • Pasta
    • White rice
    • Cakes
    • Cookies
    • Bagels
    • Pancakes
    • Waffles
    • Pizza dough
    • Hamburger/hot dog buns
  • Sugary snacks and soft drinks
  • Fatty or processed meats:
  • Non-lean beef
    • Pork
    • Ham
    • Bacon

To ensure likelihood of adherence to the food plan, researchers gave participants in the diet-change group a “hamper” of food containing items they may not have been able to afford: olive oil, natural nut butter, nuts and seeds, and the spices (turmeric and cinnamon).

After the three-week trial, they found that, compared to the control group, participants in the diet group showed significant reductions in primary depressive symptoms such as:

  • Sadness
  • Loss of appetite
  • Loss of interest
  • Poor sleep
  • Impaired thinking/concentration
  • Feelings of worthlessness
  • Fatigue
  • Suicidal ideation

They also found that, compared to the control group, participants in the diet group showed significant reductions in secondary symptoms of depression and anxiety, such as:

  • Low mood
  • Pessimism
  • Hopelessness
  • Apprehension
  • Dry mouth/sweaty palms
  • Irritability
  • Hyperarousal
  • Impatience

There you have it: three weeks of healthy eating can improve symptoms of depression. It’s also worth mentioning they confirmed that it’s possible for a group of young adults to follow a three-week dietary intervention designed to assess its impact on depression.

Diet and Mental Health: The Takeaways

I’ll reiterate what the data tells us: the food you eat – a.k.a. your diet – most definitely has an impact on your mental health. And by diet, I mean what you eat regularly. I’m not talking about “dieting” or “fad diets” or “going on a diet.” I’m talking about what you choose to eat every day, starting with breakfast and continuing right on through your midnight snack. Yes, you can have a midnight snack – but if you listen to what the scientists are telling us, that snack should not be high in sugar, nor should it be a processed meat or grain: think of things like fruits or nuts instead of cookies or candy bars.

Keep in mind that this advice, and this knowledge, is both general and specific.

The general: what’s commonly known as The Mediterranean Diet is good for both your body and your mind. It’s good for you heart, your muscles, your bones, your mood, your overall sense of wellbeing – in fact, it’s hard to find something that doesn’t benefit from this type of diet.

The specific: the same diet can significantly reduce symptoms of depression and anxiety in as little as three weeks. That’s huge. It’s huge for people diagnosed with clinical depression, and it’s huge for people who may simply feel down and want to do something about it.

It’s also huge for the patients we work with every day at Pinnacle Treatment Centers. Our patients live with substance use disorders that are often accompanied by depressed mood or a dual diagnosis of substance use disorder and major depressive disorder. This latest research tells me – and them – that changing their diet from one high in sugar, processed carbohydrates, and fatty meats to a low-sugar diet that emphasizes whole grains, vegetables, fruit, fish, and lean meatcan reduce depressed mood and symptoms of major depressive disorder.

That is definitely huge.

In a nutshell (pun intended), science says a healthy, balanced diet can make my patients happier – or at least reduce their depressive symptoms. In my experience, a happier person – or someone who’s not dealing with depressive symptoms all day every day – is more likely to proactively engage in treatment, therapy, and counseling. And when my patients can fully commit to and engage in treatment, they have a higher chance of achieving a successful, sustained recovery.

In my line of work, that’s the entire goal.

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