Can food affect our mood and overall mental health? The link between nutrition and physical health is well known, but ‘nutritional psychiatry’ – the science of the role of nutrition on our mental health – is a growing area of research. We can expect to hear a lot more around the link between food and mood in the coming years.

Depression and anxiety are the most common mental health conditions worldwide. According to the World Health Organization, 4% of the population worldwide has a diagnosed anxiety disorder, and 5% suffer from depression.

This number is probably under-reported, since unfortunately, there is still a stigma associated with mental health conditions.  Some people who experience anxiety at times may also not meet the criteria for a diagnosis, so the official numbers don’t include them.

Our brain accounts for only 2% of our body weight, but it uses more calories than any other organ – 20% of our total energy needs. It needs good nutrition to stay healthy and function optimally.

We already know that the typical Western diet doesn’t make the grade when it comes to overall nutrition and nutrient intake. While people may be eating more calories overall, diets are lower in the nutrients that the brain needs to thrive. Even so, how much are food and mood related?

Food and mood: a vicious cycle?

When we feel down or stressed, we often reach for comfort foods which tend to be higher in refined carbohydrates and lower in overall nutrition. Cross-sectional studies, which are observational and look at a single point in time, support this and have found that people who experience poor mental health also have poor eating habits.

Appetite changes are also a common symptom of major depressive disorder. Evidence shows that people with depression are more likely to eat foods high in unhealthy fats, sugar, and salt and consume less fruits and vegetables. 

Studies have shown associations between depression and anxiety disorders and poor diets which are often defined as diets high in processed high-fat and high-sugar foods and low in fruits and vegetables.

The evidence suggests that diet may contribute to an increased risk of mental health disorders, however these studies do not show causation and there have been some inconsistent findings of results. Inconsistent findings may be related to the differences in defining “diet quality or poor diets” in studies, the different groups of people in the studies (such as different age groups), and the quality of the studies. 

Are their poor eating habits the cause of their mental health issues, or the other way around? We have to be careful to look at all sides.

It’s easy to say that certain foods cause conditions like anxiety and depression, but what if these conditions facilitate the consumption of a diet that’s high in ultra-processed foods? We already know that people who have major mental health issues tend to have trouble with activities of daily living such as shopping and cooking, and sometimes can’t even get out of bed. Often, reaching for prepared foods to simply eat something is all they can do.

Are we going to blame these individuals for their situation by saying that they caused it because they ate a lot of snack foods?

That would be awful, not to mention totally untrue. Sure, diet is a piece of any health puzzle. But it’s definitely not the only piece.

We always need to consider the possibility of reverse causation. Is it the diet causing the mental health issue, or the other way around? This is an approach we rarely see in the reporting of studies in the media, because ‘X food causes Y’ headlines are a lot more compelling than ‘we don’t know.’

All that being said, research has found some positive associations between two dietary patterns and mental health – the Mediterranean Diet and the MIND diet. 

The Mediterranean diet and brain health.

The Mediterranean diet is based on the dietary patterns of people in Italy, Greece and Crete.

The diet emphasizes daily servings of whole grains, vegetables and fruits, beans and lentils, and nuts. It encourages fish and seafood a few times a week. Olive oil is the main oil used. The diet is low in red meat, sweets and pastries, and fried foods. Foods like eggs, cheese, and poultry are included, and recommended daily to weekly.

Physical activity, home cooking, and eating with others are also important components of the Mediterranean diet. 

In a literature review that looked at the Mediterranean diet and its benefits on health and mental health, authors cited two clinical trials related to following the diet and depressive symptoms. Both studies found that adopting the diet seemed to help reduce symptoms of depression and improved rates of remission.

However, both studies cited were only 3 months long. Longer-term studies would be helpful to have more conclusive information and to see how the diet holds up over time in terms of improvements. 

A meta-analysis that looked at the association between following a Mediterranean diet and the risk of depression, found that adherence to the diet helped reduce depression risk as well as other brain diseases such as stroke and cognitive impairment. 

This analysis also found a dose-response relationship: those who adhered more closely to a Mediterranean-style diet had higher risk reduction. This is important, because it seems to indicate that even making small changes such as increasing vegetables and adding a serving of fish once a week may have an impact on your mental health. 

What is the MIND diet?

The MIND diet is a newer diet that came out of Rush University in the United States in 2015.

The MIND diet is a combination of the DASH diet (which is used in the treatment of hypertension) and the Mediterranean diet. The goal of this diet is to promote brain health and help prevent the cognitive decline that is normally associated with aging.

Similar to the Mediterranean diet, the MIND diet emphasizes plant-based whole foods and limits fried foods and sweets. It is high in antioxidants that can help protect the brain from damage. 

Research on the MIND diet appears mixed.

Adherence to the MIND diet has been significantly associated with a lower chance of depression and psychological distress, but not anxiety. 

While observational studies suggest that the MIND diet has the potential to slow cognitive decline and reduce dementia risk, a recent randomized clinical trial did not find any difference between the MIND diet and a control group in terms of cognition. This study consisted of overweight or obese older adults with a family history of dementia.

Both groups had mild caloric restriction and received counseling from a registered dietitian. Both groups lost weight and had improvements in cognition. Weight loss has been shown to improve cognition in people with obesity, so this could explain why there were no differences between the two groups.

Overall, there seems to be more evidence to support the Mediterranean diet for improving mental health. Longer-term, high-quality clinical trials are needed to study this topic area further. 

THE EVIDENCE FOR/AGAINST SPECIFIC NUTRIENTS AND BRAIN HEALTH

Omega-3 fats:

Omega-3s are essential fats meaning we have to get them from food or supplements, our body can’t make them. There are three types of omega-3s:  ALA (alpha-linolenic acid), DHA (docosahexaenoic acid), and EPA (eicosapentaenoic acid). While all types of omega-3s have general health benefits, the most important one for brain health is DHA. 

Our brain is made up of over 60% fat and DHA is the most prominent fat in the brain. It accounts for over 40% of the fat in brain tissue with most of it being in the gray matter – the part that plays an important role in allowing us to function. DHA is a major structural component of brain cell membranes, plays a role in how much blood flows to the brain, and helps with neurotransmitter production. 

If our diets are too high in saturated and trans fats and low in essential fats, these unhealthy fats can take the place of where DHA should be in the brain and potentially interfere with the brain’s ability to function effectively. 

Many people are not getting enough DHA and omega-3 in general. Fatty fish such as salmon, sardines, and trout are some of the best sources of omega-3 fatty acids. 

To ensure you are getting enough omega-3’s and DHA, aim for at least two servings of fatty fish per week.

In a meta-analysis of randomized controlled trials, researchers found that omega-3 supplements reduced the severity of depressive symptoms among people with and without depression. Further analysis found that those with diagnosed depression had a greater reduction in symptoms compared to those without depression.  Omega-3 supplements also appeared to increase the odds of remission of depression, but did not reduce the risk of developing depression in those who did not have it.

The evidence for these outcomes varied between low to moderate certainty, meaning that we still have more to learn about omega-3 supplements and mental health outcomes. 

There is not currently enough evidence to recommend omega-3 supplements for depression, For now, focus on getting omega-3 from your diet. Fatty fish, soybeans, flax, chia seeds, and walnuts are all sources of this fatty acid.

Vitamin B12:

B vitamins such as thiamine, folate, and B12 are important for mental health. These vitamins play a role in neurotransmitter production, and help maintain healthy brain cells. Symptoms of B vitamin deficiencies can include depression, anxiety and cognitive decline. While it’s not common for people to be deficient in vitamins B1, B2, and B3, vitamin B12 deficiency is far more common, in particular in older individuals.

This is due to the fact that as we age, we absorb vitamin B12 less efficiently.

Studies have also found high rates of folate and B12 deficiency in people admitted to the hospital for psychiatric reasons. 

Generally, a varied diet with lots of colorful fruits and vegetables, whole grains, and lean meats will cover the B vitamins. B12 is an exception: it’s only found in animal foods as well as fortified foods as such almond or soy milk.  

Choline:

Choline is a B vitamin that has been gaining more popularity recently. Choline is important for brain health throughout the life cycle. 

Choline is needed to make acetylcholine, a neurotransmitter for mood, memory, muscle control, and other brain functions. 

Our liver can make some choline, but we also need to get it from food. Eggs, meat, fish, poultry, and dairy products are good sources of choline. Some vegetables such as broccoli and cauliflower and some beans, nuts and seeds also have choline. 

There is no evidence to suggest that taking choline supplements is beneficial for mental health, so focus on getting it from food to support brain health. 

Vitamin D:

Vitamin D deficiency has been associated with mental health conditions including depression and ADHD however there is inconclusive evidence on its use as a component of treatment.

If you live in Canada or a climate where you do not get sun exposure for significant parts of the year, a vitamin D supplement is likely a good idea anyway. 

Is gut health linked to mental health?

We are only beginning to scratch the surface of how gut health can impact our mental health. 

The “gut” refers to the intestine, mainly the large intestine which is where most of the microbiota are. Microbiota includes bacteria, viruses, yeast, and fungi and our gut is home to trillions of them.

Microbes can be beneficial or harmful, and we aim to have a variety of good ones to outnumber or outweigh the harmful ones. 

Although we suspect a link between gut health and mood, research in that area has not yet proven causation. Of course, optimizing gut health with a diet full of plants and fibre, and decreasing alcohol and saturated fats, sugar, and refined carbs, is never bad advice.

The GAPS diet is a diet that was developed to ‘treat’ ASD, and is predicated on the belief that ‘leaky gut’ and gut dysbiosis cause a multitude of different diseases and conditions, including mood disorders.

I reviewed the GAPS diet here, and found it restrictive and based on pseudoscience.

Our gut and our brain are in constant communication and this is known as the “gut-brain axis.” Most of our serotonin, the neurotransmitter that helps boost our mood, is produced in the gut. 

Fibre feeds the good bacteria in our gut. Including fiber and also fermented foods such as sauerkraut, kefir, and kimchi can also help maintain gut health.

Research has focused on the use of probiotics as a means to improve mental health. Probiotics are live bacteria and yeasts that are similar to the good microbes in our gut. Probiotics can be found in some foods, and also in supplements.

 In a systematic review of studies that evaluated the use of probiotics on depression and anxiety, half of the studies that looked at depression, stress or anxiety reported improved symptoms following probiotic intake. 

This study (and this one) found that probiotics improved stress levels and cognition in elderly subjects.

I’ve written more about probiotics, fermented foods, and the gut microbiome here. 

While there are human studies suggesting that probiotic use may have a positive impact on depression, most of these studies are small, and use specific probiotic strains. We just don’t have enough evidence to make specific claims. If you see a company making these claims, please beware.

Amare and Velovita are a multi-level marketing companies claiming that their supplements improve mental health.

My Amare review holds up the company’s claims against the research. Read it here.

Here’s my Velovita review.

There’s nothing more repugnant IMO than people trying to line their pockets by convincing others to come off of their psych meds.

FOOD and mood, bottom line:

Adopting principles of the Mediterranean diet may have a positive impact on mental health. This diet encourages plenty of plant-based, whole foods as well as fish that are high in omega-3 fats that the brain needs to function at its best.

Limit ultra-processed foods. This doesn’t mean STOP eating them altogether, but do your best to eat less of them.

Small dietary changes can have an impact – it doesn’t have to be all or nothing. 

You may want to consider omega-3 supplements if you don’t eat fish. Talk to a doctor or dietitian before starting supplements. 

*Dietary changes are not a substitute for medical treatment of mental health disorders. If you are suffering or experiencing symptoms of depression, anxiety or any other mental health concern, please get help from a qualified medical professional.