Way back when I first started Healthy Emily, I wrote a blog post about how eating different foods could affect our brains’ production of neurotransmitters that affect mood. This post was, and still is, one of the most popular posts on this site. About two years after I wrote it, I took a Food Science class that asked us to write a term paper on a topic relating to, as you might assume, food and science. Since the topic of nutrition and mood stability still fascinated me, I decided to turn the idea for that post into my term paper.
Since the post was so popular, I thought I would share with all of you the final results of my paper, with the actual, scientific research that answers the question:
Can dietary changes positively (or negatively) affect mood at a neurological level?
Here is part one of the paper – click here to read part two!
Nutrition’s Effects on Mood
by Emily Star
written May 2015
The human brain produces chemicals called neurotransmitters, which are one way that the body communicates within itself and causes function1. There are many different neurotransmitters, and they all provoke or prevent different types of reactions in the body. The three that most influence mood are dopamine, norepinephrine, and serotonin. Dopamine and norepinephrine are excitatory (they provide energy, alertness, and focus), and serotonin is inhibitory (it causes feelings of calm and relaxation)1. These three types of neurotransmitters are called biogenic amines1. Ideally, all three should work together to create a happy, healthy person who is well-balanced and able to handle daily stress without becoming overly depressed or anxious.
Put very simply, brain cells, or neurons, send neurotransmitters back and forth to communicate1. Two nerve ends (synapses) are near each other1. One releases an amount of a neurotransmitter (e.g. serotonin) into the space between them, which is called the synaptic cleft1. The other synapse absorbs the amount of serotonin it needs, and then various enzymes are released to clean up the leftover serotonin in the cleft that’s unneeded1.
What someone suffers from depression, often it is because the nerves are unable to tell exactly how much serotonin needs to be taken in. Too much is left in the cleft and cleared away by the enzymes, and not enough is taken up by the second synapse1. Alternatively, or simultaneously, the first nerve may not be producing enough in the first place. This progresses on from nerve to nerve. Anti-depressants and anti-anxiety medications alter this neural pathway. Some, called SSRIs (selective serotonin reuptake inhibitors),2 cause the receiving neuron to take up more neurotransmitter from the synaptic cleft than it normally would.2
The body uses specific nutrients to make the various neurotransmitters, mostly amino acids2. These are broken down and sent to the brain, where they are made into neurotransmitters2. This leads to the question: can dietary changes – that is, increasing the intake of foods containing the amino acids used to make serotonin, norepinephrine, and dopamine so that there is more available to the brain to use3 – positively affect mood? And can decreasing dietary intake of these foods negatively affect mood?
Review of Literature
Seeley’s Anatomy and Physiology is a textbook used in introductory level Anatomy and Physiology classes. It provides a basic overview of the nervous system and details about how neurons and neurotransmitters work.1 It gives a good introduction to the basics of this topic.
Parker and Brotchie’s article, “Mood effects of the amino acids tryptophan and tyrosine,” goes more in depth regarding the way the body uses amino acids to produce neurotransmitters, particularly tryptophan (serotonin) and tyrosine (norepinephrine/dopamine).2 In addition to explaining how this works, they also provide a good overview of other research done into whether “any deficiency [in these nutrients] increases risk to depression and whether those amino acids have any antidepressant properties.”2
In their article for Pakistan Veterinary Journal, Moin et al. study “the relationship between adaptation to stress and macronutrient intake,” or how serotonin is produced in response to stressors.3 The study was performed on rats. They also give a good overview of exactly how the body uses macronutrients to produce neurotransmitters that affect mood (serotonin, norepinephrine, dopamine).3 Choi et al. study the “Effect of chronic protein ingestion on tyrosine and tryptophan levels … and serotonin synthesis in rat brain.”4 They studied rats to find out how, when various proteins are added to the diet regularly, they affect tryptophan levels and serotonin synthesis.4
Finally, in their article for Nutritional Neuroscience, Kirac et al. examined how a high-fat diet in rats affected 5-HIAA levels, which is a byproduct of the breakdown of serotonin.5 By studying the diet and 5-HIAA levels, this group of researchers found how it (the diet) affected serotonin development in the rats’ brains.
To be continued next week with specific info on carbs, fats, and protein.
- VanPutte, CL, Regan, JL, et al. Seeley’s Anatomy and Physiology. New York: McGraw Hill; 2014:384-399.
- Parker G, Brotchie H. Mood effects of the amino acids tryptophan and tyrosine: ‘Food for Thought’ III. Acta Psychiatrica Scandinavica [serial online]. December 2011;124(6):417-426. Available from: MEDLINE with Full Text, Ipswich, MA. Accessed April 23, 2015
- Moin S, Haider S, Khaliq S, Tabassum S, Haleem D. Behavioral and Neurochemical Studies in Stressed and Unstressed Rats Fed on Protein, Carbohydrate and Fat Rich Diet. Pakistan Veterinary Journal [serial online]. June 2012;32(2):260-264. Available from: Food Science Source, Ipswich, MA. Accessed April 23, 2015.
- Choi S, DiSilvio B, Fernstrom M, Fernstrom J. Effect of chronic protein ingestion on tyrosine and tryptophan levels and catecholamine and serotonin synthesis in rat brain. Nutritional Neuroscience [serial online]. November 2011;14(6):260-267. Available from: Food Science Source, Ipswich, MA. Accessed April 23, 2015.
- Kirac D, Ozden I, Yildirim A, Genç E. Effect of high-fat intake on motor activity, homovanillic acid and 5-hydroxyindoleacetic acid levels in striatum and cortex of rats exposed to stress. Nutritional Neuroscience [serial online]. April 2009;12(2):89-94. Available from: Food Science Source, Ipswich, MA. Accessed April 23, 2015.