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The Link Between Nutrition and Mental Health: An Interview with Kelly Matheson


By Jeffrey Lynham

The importance of food is obvious—it provides energy and nutrients for our bodies to grow and develop in order to be active and healthy. Eating certain foods, however, can lead to poor physical health conditions such as heart disease, type II diabetes, obesity, and high blood pressure. But what about mental health conditions? To find out more about how nutrition can affect our mental health, I spoke with Centre for Addiction and Mental Health (CAMH) Registered Dietitian Kelly Matheson.

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You work as a Dietitian for CAMH, so there must be a link between diet and mental health. Can you talk a bit about that?

There’s emerging evidence around the role nutrition plays in mental health. It's a new area, but it's really exciting that it's become an interest in a lot of people. One area that people are researching has been the role of specific nutrients in improving, preventing, or treating mental illness. I'll use vitamin D as an example. A lot of research has shown that low levels of vitamin D is directly linked to depressive symptoms1. That kind of research looks at how can we supplement people with vitamin D and how that could possibly improve symptoms of depression.

A second research area is looking at how certain patterns of eating or certain types of diets can assist in the prevention, treatment and management of mental illness. One of the diets that is looked at a lot in mental health is the Mediterranean style of eating because it's one of the only diet patterns that has been shown, through randomized control trials, to lower depression scores2.

There's also another diet called “The Mind Diet,” (see below) which is an adaptation of the Mediterranean-style way of eating. It has been shown to prevent Alzheimer's and dementia from developing3,4. These diet patterns are exciting because although the other research looks at nutrients like vitamin D, we don't eat nutrients, we eat food. Diet patterns and recommendations to eat specific foods are more realistic for people to apply in their everyday lives.

A third research area is the brain gut connection. The gut-brain axis (how our brain communicates with our gut and vice versa) shows that our gut health is directly related to our mental health. They used to think that our gut was just an inert object, but now they're showing that our gut and brain are connected by blood vessels and nerves. They communicate to each other in a two-way street. They've shown that substrates made by the gut, like short-chain fatty acids, can travel to the brain across the blood-brain barrier and impact our mood. The gut can also produce neurotransmitters like serotonin.

Finally, there’s also research looking at food in a way that's not just about the nutrients that we eat, but also the social and emotional part of food too. One of the jobs that I do here is to facilitate gardening and cooking groups. It’s a cool form of therapy because there's a lot of good research to show when people are involved in producing or cooking their own food, they automatically make healthier choices, and that has a positive mental component to it. Our cooking groups are one of the things that a lot of our patients look forward to. They get to sit around a big table and eat together. We choose cultural foods that people like, and it brings a more positive experience than eating alone.

How can certain diets, like the standard American diet, affect our mental health?

When looking at how diet affects mental health, we can use depression as an example. Depression often occurs when there's an imbalance of neurotransmitters. Medications target neurotransmitter levels, which can impact our mood, our feelings of euphoria, and our feelings of contentment. When those neurotransmitters are low, that can make us feel unwell. Foods that are high in simple sugars and fat, our so-called comfort foods—chips, chocolate and cake—all those things we crave because it's a natural part of our physiology. When we eat them, they can temporarily increase those feel-good neurotransmitters, which is why people tend to crave them when they’re feeling bad because it gives them that instant energy. When you suddenly stop, it’s normal to crave those foods. The same process happens when people are recovering from drugs or alcohol.

Also, a lot of people who have depression, they’re on these medications that make them feel sedated and tired, and again, it's natural to crave those foods because they give those instant energy boosts. A lot of our patients here are really into coffee, sugar, and cigarettes, because these are things that give them that energy boost. With the Mediterranean diet, we know that these foods have lots of nutrients for the synthesis of neurotransmitters. It’s important to get these nutrients because they're going to build those feel-good neurotransmitters, and they're going to keep them high for longer versus the high followed by a sugar crash.

Another component around nutrition and mental health is markers of inflammation. A standard American diet is considered to be more pro-inflammatory. When you have high levels of simple sugars, fat, and salt, it can increase inflammatory markers. There's a lot of research to show that these inflammatory markers may cross the blood-brain barrier, which can impact our mood. The Mediterranean diet, which includes a lot of vegetables, fruits, essential B vitamins, Omega-3s, vitamin D, and healthy proteins, these are more anti-inflammatory.

What is your view on supplements? What supplements do you recommend for optimal mental health?

If you have an overall healthy diet, then most nutrients you can get through food. There are a few exceptions, and it also depends on the way you eat. If you follow a vegan diet, for example, there are certain nutrients you have to be aware of and you may have to supplement depending on what you buy and what you like to eat.

The one supplement I do recommend is vitamin D. We know that vitamin D has direct links to depression scores1. Between October and April, we don’t synthesize enough Vitamin D because of where we’re at in the world. The only products in Canada that are fortified with vitamin D are cow's milk, fortified soy milk, and other fortified milks like almond and hemp milk. I usually recommend 1000 IU a day, but a cup of fortified milk has only 200 IU. Unless you're drinking five cups of milk or milk alternatives every day, you're not going to meet those needs.

What is the most rewarding part of your job? Do you have any particular experiences you would like to share?

A lot of the patients here are very marginalized. They may be homeless, they may have no social supports, they may be so ill that they don't know why they're here or why they're taking medication. Some patients may not like talking about medications or where they're going to live. They don't like talking about the fact they can't go outside, but everybody likes talking about food. It's something that everybody has in common. I have seen that talking about food and providing healthy food through cooking groups impacts people in positive ways.

Every summer, we have our gardening program. Volunteers come in to help us plant our garden in May, and then we use the garden all summer. We use the produce in our cooking groups every week. We change what we’re making based on what’s available in the garden. I had a younger guy who was focused on a healthy lifestyle. He wanted to eat well and work out; this was integral to his mental health. He said going to the garden before our cooking group and grabbing fresh produce was the best part of his stay here. He said he always looked forward to it, and it was such an important part of his recovery. People are now realizing how much food matters in their recovery. I admit that sometimes hospitals are lagging behind in the food provided for patients, but if I can make that better by supplementing from our garden and involving people in cooking, I’m hopeful it makes their stay a lot better.

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1. Penckofer, S., et al. Vitamin D and depression: where is all the sunshine? Issues in mental health nursing 31, 385-393 (2010).

2. Jacka, F.N., et al. A randomised controlled trial of dietary improvement for adults with major depression (the ‘SMILES’ trial). BMC Medicine 15, 23 (2017).

3. Morris, M.C., et al. MIND diet associated with reduced incidence of Alzheimer's disease. Alzheimers Dement 11, 1007-1014 (2015).

4. Morris, M.C., et al. MIND diet slows cognitive decline with aging. Alzheimers Dement 11, 1015-1022 (2015).

Edited by Benjamin Bandosz & Kate Rzadki