Can an Apple a Day Keep the Psychologist Away?
I recently asked Clinical Psychologist Dr. Kate Brookie if she would share some thoughts from her PhD research on nutrition and mental health. Her research focused on micronutrients from fruits and vegetables. Here’s some tips and tricks from her research findings.
Let’s talk about scurvy, shall we? Trust me, I promise it’s relevant. Scurvy is extremely rare these days, but back in the 1700s it was a huge issue facing men and women at sea. We now know that scurvy is caused by a deficiency in Vitamin C – but we didn’t know that back then. A man called James Lind was working as a surge on a ship and he decided to test a number of different treatments for the illness – one of which included oranges and lemons. We know scurvy is largely a physical disease but causes psychological symptoms too, mostly irritability, anxiety and fatigue. And James Lind discovered that scurvy could be cured with lemon juice. This example is important because it showcases, so simply, how food (in this case, fruit) can have a profound effect on the way we feel, both physically and mentally.
I believe many of us have an intuitive understanding about our bodies. We often know that the food we eat can have influence the way we feel. For example, most of us have experienced that sluggish feeling after having a big greasy meal at lunch time; the spring in our step after eating a healthy salad; or the anxious shakes after having one too many coffees.
Most of us know this about ourselves; and science is starting to catch up. While healthy diets have been consistently linked to improvements in physical health (e.g., cardiovascular disease); we are starting to make significant links between our current diets and psychological health. While we don’t know exactly how food influences our mental state, we have some fairly plausible ideas. One of the main hypotheses is that the micronutrients found in food serve as ‘precursors’ to the manufacture of important brain chemicals that are involved in mood.
Brain chemicals – otherwise known as neurotransmitters – help the brain with countless physical and psychological functions including our heart rate, sleep, appetite and emotions. For example, dopamine is a neurotransmitter that, amongst other things, underlies energy, motivation, attention and mood. We know that dopamine needs Vitamin C to function properly. Neurotransmitters involved in managing our “fight or flight” response need an array of B-Vitamins to be able to help our bodies respond appropriately in times of stress. What’s more, Zinc underlies almost all major neurotransmission systems involved in our emotional experience. Long story short – these little nutrients play a big role in the functioning of our bodily systems implicated in mood and wellbeing.
Some researchers argue that mental difficulties such as low mood and stress could be the product of errors in these chemical systems, whereby they don’t function at their best. A diet rich in these nutrients could promote this optimal functioning and protect against the damaging effects of mental ill health.
Let’s explore the role of fruits and vegetables
When you look across the world at healthy diets there is one major common denominator – fruit and vegetable consumption. My PhD research focused on the role of fruit and vegetable consumption as a significant proportion of these vital nutrients come from consumption of plant based foods.
Over a number of studies, we found that increasing intake by as little as 1 - 2 additional servings per day resulted in improvements in a wide range of mental health domains – positive mood, concentration, motivation, and feelings of fulfilment and purpose in day-to-day living. Other cornerstone studies (e.g., Jacka at al., 2017) have shown that small dietary changes (including more fruits and vegetables) reduced levels of depression and anxiety over a number of weeks. Fruit and vegetable consumption has been linked with lower levels of stress, depression, negative mood, anxiety, negative effects of bipolar symptoms, ADHD, and post-natal depression. The list could go on. It also appears that the most benefit comes when you eat more than the standard 5+ a day. In fact, the most mental health benefits are seen in those eating 8 – 10 servings daily.
And with that, here is the first tip – boost up your daily plant intake.
So, plants and their micronutrients are important. What about these superfoods we often hear about? Just the other day I read an article about how blueberries were the new ‘miracle brain food’. While this kind of narrative is very tempting, it is important that we don’t slip into magic bullet thinking. Julia Rucklidge, a leading researcher in this area, encourages us to consider variety and diversity of nutrients rather than looking for one miracle vitamin or mineral that promises to fix everything. Instead, try and include a number of different types of fruits and vegetables. Dr Drew Ramsey, a nutritional psychiatrist, advocates for eating the rainbow in order to maximise the type and variety of nutrients you are receiving through diet. This sort of diversity of consumption is also important in maintaining a population of healthy gut bacteria, which also plays an important role in promoting mental wellbeing.
So there is the second tip – eat plants, but make sure there is variety.
My most recent PhD research focused on the effect of eating raw versus cooked/canned/processed fruits and vegetables. We know that cooking or processing foods may alter the availability of various nutrients. Water soluble vitamins such as Vitamin C and B-Vitamins are particularly vulnerable to heat, meaning that some of the beneficial micronutrients may be lost when these foods are cooked (e.g., spinach, broccoli, green beans). Fat soluble nutrients such as Vitamin A, D, E, and K are less susceptible to heat so cooking may not be as damaging. Finally (and somewhat confusingly!), cooking can actually enhance the availability of some antioxidants due to thick cell walls being effectively broken down by heat. For example, foods rich in beta-carotene (e.g., carrots) and lycopene (e.g., tomatoes) may be better for you when they have been cooked. Evidence has also shown that longer storage times for canned fruits and vegetables can reduce the nutrient profiles. Other forms of processing – such as frozen fruits and vegetables – may not be as bad as they tend to be snap frozen when they are freshest.
Third tip of the day – eat your plants in a way that maintains the most nutrients.
If you do need to cook your vegetables, try lightly steaming them
If you do need to boil your vegetables, use less water, reduce the cooking time, and leave your vegetables in large pieces to reduce the surface area
Try and eat your fruit and vegetables fresh and seasonal
Store your fruits and vegetables appropriately – potatoes and canned foods should be kept in cool dark places, whereas leafy greens should be refrigerated
Don’t worry so much about cooking foods like carrots and tomatoes – cooking may actually increase the availability of their nutrients
Our diets have changed dramatically over the past 100 years, and somehow we’ve become one of the most overfed but undernourished cohorts in history. What’s more, our mental health is in a state of global crisis. While traditional interventions and mental health services are doing their best to address this very serious issue, we need to continue to find new ways to tackle these problems. Especially when traditional methods are not working for everyone. By no means do I believe diet is the be-all-and-end-all of mental health and wellbeing. However, small dietary changes that are achievable and sustainable over a long period of time may provide clients with a ‘buffer’ that allows greater resilience when times do get tough.
References
Brookie, K. L. Can an apple a day keep the psychologist away? The role of fruit and vegetable intake in mental well-being. Submitted in fulfilment of Doctorate of Philosophy, University of Otago. Available for download at: https://ourarchive.otago.ac.nz/handle/10523/8020
Brookie, K. L., Best, G. I., & Conner, T. S. (2018). Intake of raw fruits and vegetables is associated with better mental health than intake of processed fruits and vegetables. Frontiers in Psychology, 9, 487.
Brookie, K. L., Mainvil, L. A., Carr, A. C., Vissers, M. C. M., & Conner, T. S. (2017). The development and effectiveness of an ecological momentary intervention to increase daily fruit and vegetable consumption in low-consuming young adults. Appetite, 108, 32-41.
Conner, T. S.,+ Brookie, K. L.+, Carr, A. C., Mainvil, L. A., & Vissers, M. C. M. (2017). Let them eat fruit! The effect of fruit and vegetable consumption on psychological well-being in young adults: A randomized controlled trial. PLOS ONE, 12(2), e0171206
Conner, T. S., Brookie, K. L., Richardson, A. C., & Polak, M. A. (2015). On carrots and curiosity: Eating fruit and vegetables is associated with greater flourishing in daily life. British Journal of Health Psychology, 20, 413-427.
Dash, S., Clarke, G., Berk, M., & Jacka, F. N. (2015). The gut microbiome and diet in psychiatry: focus on depression. Current Opinion in Psychiatry, 28(1), 1-6.
Jacka, F. N., O’Neil, A., Opie, R., Itsiopoulos, C., Cotton, S., Mohebbi, M., ... & Brazionis, L. (2017). A randomised controlled trial of dietary improvement for adults with major depression (the ‘SMILES’ trial). BMC Medicine, 15(1), 23.
Kaplan, B. J., Crawford, S. G., Field, C. J., & Simpson, J. S. A. (2007). Vitamins, minerals, and mood. Psychological Bulletin, 133(5), 747. doi: 10.1037/0033-2909.133.5.747
