We already know that what we eat is related to how we feel physically including health problems such as obesity, diabetes, and coronary heart disease. However, newer research is showing that diet and nutrition are also directly related to our mental health. Learn about research being conducted showing links between diet and mental health, discover some of the barriers to healthy eating, and uncover a few ways to get your healthy eating on track.
What is Healthy Eating?
This post is going to talk a lot about healthy eating, so it is probably helpful to first define what is meant by that term. Healthy eating emphasizes eating a variety of vegetables, fruits, whole grains, and fat-free or low-fat dairy products which include milk, yogurt, cheese, and/or soy products. In addition, healthy eating includes protein sources such as lean meats and poultry, seafood, eggs, legumes (beans and peas), nuts, seeds, and soy products.
Healthy eating should limit the amount of saturated fats, trans fats, sugar, and sodium consumed (I know, ruins all the fun). Lastly, healthy eating should stay within a person’s daily caloric intake needs which is approximately 2,500 calories per day for men and approximately 2,000 calories per day for women, although these numbers vary depending on an individual’s activity level and age.
Most likely none of that information is shocking, for the most part we have been told similar information our whole lives. Yet, no matter how easy healthy eating sounds in theory, in practice it is quite difficult to maintain a good diet every week for a variety of reasons.
Before looking at some ways to help improve the way we eat, let us look at what the latest research says regarding the connection between healthy eating and mental health and why this connection exists.
Healthy Eating and Mental Health
Researchers around the world are examining the link between healthy eating and mental health. Some studies are highlighted below that have examined this link.
One study used a sample of 5731 Norwegian adults and looked at how diet quality is related to depression and anxiety (Jacka et al., 2011). After accounting for factors such as age, education, income, physical activity, smoking, and alcohol consumption, the researchers found that having a healthier diet was associated with less depression and anxiety for women and less depression for men. In this study a healthier diet was characterized by eating vegetables, fruits, low-fat dairy, whole grains, fish, and unprocessed red meat.
An important note is that it is often difficult to tease apart why a link between two factors exist. In statistics, one of the most popular sayings is correlation does not lead to causation (something I will likely explain in a different post). In essence, it is difficult to determine whether it is the healthy diet that is leading to reduced depression and anxiety or whether it is something associated with having a healthy diet (i.e., having a higher income) that is related to the mental health symptoms.
What I appreciate about the study by Jacka and colleagues is that they accounted for a bunch of different factors that could be related to mental health, including two indicators of socioeconomic status (i.e., education and income). By doing so, it strengthens the argument that a healthy diet is directly related to mental health. Let us look at some other studies that have found similar connections.
In a study of 3486 British middle-aged adults, diets were separated into whether a person ate more ‘whole foods’ characterized by a high intake of vegetables, fruits, and fish, as opposed to a ‘processed foods’ profile characterized by a high consumption of sugar, fried food, processed meat, refined grains, and high-fat dairy products (Akbaraly et al., 2009).
What this study found was that having more of the whole foods diet predicted lower depression scores five years later and having more of the processed foods diet predicted higher depression scores five years later, after controlling for a lot of related factors including gender, age, marital status, employment, education, physical activity, and several physical diseases.
The last study that will be discussed in this section examined whether international dietary trends (from a variety of countries including the USA, Canada, Colombia, Nigeria, India, and Taiwan) predict schizophrenia outcomes and the prevalence of depression (Peet, 2004).
What the researchers found was that higher intake of refined sugar and dairy products predicted worse outcomes for those with schizophrenia and lower levels of fish and seafood intake predicted higher rates of depression across the different countries.
Now, I admittedly have difficulty believing that having higher rates of sugar consumption nationally directly leads to worse schizophrenia symptoms and it is likely that in this case sugar consumption is a proxy for other, more salient cultural factors. Indeed, as far as I can tell, other important factors were not controlled for in this study such as national gross domestic product (GDP) or national availability of services to treat mental health problems.
However, the research linking fish consumption to rates of depression seems to be in line with other research that is discussed below.
Regardless of the problems with the previously mentioned study, the link between healthy eating and mental health appears to be present across the world and deserves closer examination. It will be interesting to see if/how different organizations around the world try to tackle mental health problems through healthy eating.
Now that we understand there is a link between healthy eating and mental health, let us try to unpack what some of the reasons are for this relationship.
Understanding the Links Between Eating and Mental Health
To understand why healthy eating is related to mental health, we have to dive a little bit into nutrients and brain biology.
A literature review (where researchers look at a bunch of different studies and summarize the findings) of the impact of nutrition on depression in samples of childbearing-aged women found that several nutritional factors are related to mental health (Bodnar & Wisner, 2005). The following conclusions were highlighted in the review:
Poor omega-3 fatty acid status increases the risk of depression. Fish oil and folic acid supplements each have been used to treat depression successfully. Folate deficiency reduces the response to antidepressants. Deficiencies of folate, vitamin B12, iron, zinc, and selenium tend to be more common among depressed than nondepressed persons. Dietary antioxidants have not been studied rigorously in relation to depression.
Essentially, while there is not much evidence supporting the protective role of antioxidants with relation to depression, many other nutritional factors are very important for preventing and treating depression.
While the details of why these nutrients lead to improved mental health get fairly complicated, essentially they are important for a variety of functions in the brain, including the creation of neurotransmitters (chemicals in the brain), impacting how well neurons signal to each other, and affecting how efficiently neurotransmitters are used by neurons.
Basic anatomy of a neuron
Another body of research suggests that the link between healthy eating and mental health may be related to growth of new brain cells, called neurogenesis, in an area of the brain called the hippocampus (Zainuddin & Thuret, 2012). The hippocampus is a part of the brain that is important for memory, learning, and emotions. Accordingly, the hippocampus plays a key role in mental health conditions such as depression and schizophrenia.
How is diet related to the hippocampus? Well apparently diet-related factors such as consuming omega-3 fatty acids (e.g., salmon, sardines, walnuts, flaxseed), polyphenols (e.g., blueberries, coffee, dark chocolate, strawberries, cumin, red wine), minerals (i.e., zinc), and vitamins (i.e., vitamin A) are all related to neuron growth in the hippocampus. Other factors such as having a high-fat diet are apparently related to less new cell growth in the hippocampus.
Taken together, this research shows us that nutrition is directly related to how well our brain works and grows, which helps explain the link between healthy eating and good mental health. Now that we have explored the importance of healthy eating, let us look at different barriers that can get in the way of healthy eating.
Barriers to Healthy Eating
Researchers have used something called the Health Belief Model to understand why people do not eat well. The Health Belief Model looks at a few different constructs to understand why people choose or choose not to eat well.
These constructs include perceived susceptibility, which is the likelihood that one will have negative consequences due to poor eating (i.e., how likely you will get diabetes or become overweight), perceived severity, which is how serious problems related to poor eating will be, perceived benefits, which can be difficult when benefits are longer-term or uncertain, perceived barriers, which could include lack of access to fresh food or lack of cooking knowledge, and cues to action, which are things that increase readiness to make changes (e.g., when you no longer fit into your old jeans, taking a cooking class).
Self-efficacy, which is often included in the Health Belief Model, is a very important construct for a variety of different concerns, not just healthy eating. Self-efficacy is the belief that one can actually do a particular behavior.
For example, if someone has low self-efficacy for cooking, that person will not believe that they can follow a recipe and come out with a nice meal. As such, a person with low cooking self-efficacy is going to be less likely to actually attempt to cook a meal because they are expecting to fail at it. It is important to note that self-efficacy is different from someone’s actual skill level, it just refers to how capable a person feels at a certain task.
As you can see, the Health Belief Model is made up of a bunch of different constructs, all of which can be really important in determining whether someone makes healthy food choices.
There are many other factors not related to the Health Belief Model that can impact healthy eating, such as perceived levels of stress. I am guessing that we have all had the experience of not wanting to cook after a long and stressful day, and instead indulge in some comfort food (a.k.a. something fried, delicious, and fast). There is not much of a problem with the occasional indulgence, but when it becomes an everyday routine, then the quality of our diet is negatively impacted.
Other barriers are most systemic, such as the presence of food deserts, where there is a lack of access to fresh produce that is especially common in more impoverished communities, in addition to general high cost of buying fresh ingredients. These barriers are very much real and need to be addressed, however they are harder to address on the individual level and so are not the focus of this post.
Alright, say we recognize the importance of healthy eating and want to make some positive changes, what is the best way to go about it?
Tracking Your Food Intake To Promote Healthy Eating
So maybe you have identified that your diet could be improved a little bit (and let us be honest, we could all probably improve our diet in some way); it is important to know the best ways to go about making a change.
A group of researchers examined 101 research papers, which included over 44,500 participants, that looked at interventions for healthy eating and exercise (Michie et al., 2009). Of all the different techniques used in the interventions, self-monitoring was identified as the most powerful technique.
Self-monitoring your diet is just what it sounds like, keeping track of what you are eating. Sounds simple, but this is a technique that has been shown time and time again to work well. Through self-monitoring, people become more aware of their diet, notice patterns, and tend to make healthier choices because of this increased awareness. Personal examples include feeling kind of guilty when you realize how often you eat frozen pizza or when you learn how many calories are in your beloved macaroni and cheese (which again is not to say you cannot have these meals in moderation) and making some appropriate changes accordingly.
The nice thing about self-monitoring is that you get to pick what works for you. In treatment I often give clients print-outs of weekly calendars so that we can track progress over the previous week. Given how common smartphones are now, there are also several different apps that people use. I have not personally or professionally used any of these apps yet, but a quick web search can find several popular apps that might work for you (e.g., http://lifehacker.com/five-best-food-and-nutrition-tracking-tools-1084103754).
Getting back to that huge study that looked at interventions for healthy eating and exercise. While the researchers found that self-monitoring was the most powerful technique, they also found that interventions that used both self-monitoring AND another technique that targets self regulation such as intention formation, specific goal setting, getting feedback on performance, and/or reviewing behavioral goals. Let’s look at them one by one briefly.
The technique intention formation is helping an individual to make a behavioral resolution. An example of this might be if someone says “I will eat a salad for lunch on Monday.” The technique of specific goal setting is like intention formation, but goals can be a bit more broad. For example, someone might have the goal of “eating healthier.” However, this is an extremely broad goal and is probably not going to be all that helpful when it comes to making concrete changes. This goal of “eating healthier” can be broken down into smaller goals that are specific and easier to achieve. An example of a more specific goal may be to “eat more vegetables”, which can be broken down to an even smaller goal to eat a salad for lunch three times in a week.
Getting feedback on performance is again pretty self-explanatory, it helps when you can know how you are doing in relation to your goals. For example, if a nutritionist lets you know that you have lost or gained weight and that is related to a goal of yours, then you can learn what you might need to do differently or keep the same to achieve your goal.
Lastly, reviewing behavioral goals is when you check back on your goals and change them as needed. Say you realize you hate eating salads for lunch, but perhaps figure out that you love veggies and dip. Your revised goal might be to have veggies and dip with lunch so that you are still getting your servings of vegetables.
Well we covered a lot of information, so what is the big picture? First of all, eat your gummy vitamins. Half-kidding - the best source of nutrients is from food and not supplements. Really what it comes down to is that what we eat has a huge impact on how we feel. We have all heard the saying, “You are what you eat” and this appears to be true both physically as well as mentally. Diets that are healthier and include necessary vitamins and minerals are related to better mental health.
Truth be told almost all of our diets could be better. This post is not here to blame or make anyone feel bad about their diet. In addition, it is not my suggestion that you start some new fad diet to eat healthier (there is some great research about how crash dieting is really bad for our bodies). Instead, I am encouraging myself and encouraging each of you to make some small lifestyle changes to try to improve the quality of food that we eat.
Thankfully if you are interested in learning more about healthy eating, there are a ton of free resources online and in communities. Some grocery stores now even have dietitians that you can meet with for free to talk about healthy eating and who will provide easy recipes that are healthy, cost-effective, and delicious.
One of the big takeaways that I learned from this research is just how important omega-3s are for mental health. I knew in general that omega-3s were important, but after looking at the research, it does make me want to be more conscientious about my omega-3 intake.
Hopefully you also were also able to learn something new. It seems like research in this area still needs to be further developed in terms of understanding all of the biological pathways that explain the relationship between nutrition and mental health, but for the moment I think we can all agree that eating a little healthier is going to help us feel a little bit better in our everyday lives.
The Clinically Relevant Insights Blog, part of ShawnWilsonPhD.com, shares news and research related to psychology and wellness.
Akbaraly, T. N., Brunner, E. J., Ferrie, J. E., Marmot, M. G., Kivimaki, M., & Singh-Manoux, A. (2009, 10). Dietary pattern and depressive symptoms in middle age. The British Journal of Psychiatry, 195(5), 408-413. doi:10.1192/bjp.bp.108.058925
Bodnar, L. M., & Wisner, K. L. (2005, 11). Nutrition and Depression: Implications for Improving Mental Health Among Childbearing-Aged Women. Biological Psychiatry, 58(9), 679-685. doi:10.1016/j.biopsych.2005.05.009
Jacka, F. N., Mykletun, A., Berk, M., Bjelland, I., & Tell, G. S. (2011, 07). The Association Between Habitual Diet Quality and the Common Mental Disorders in Community-Dwelling Adults. Psychosomatic Medicine, 73(6), 483-490. doi:10.1097/psy.0b013e318222831a
Michie, S., Abraham, C., Whittington, C., Mcateer, J., & Gupta, S. (2009). Effective techniques in healthy eating and physical activity interventions: A meta-regression. Health Psychology, 28(6), 690-701. doi:10.1037/a0016136
Zainuddin, M. S., & Thuret, S. (2012, 07). Nutrition, adult hippocampal neurogenesis and mental health. British Medical Bulletin, 103(1), 89-114. doi:10.1093/bmb/lds021