Food, mood and health: a neurobiologic outlook
Bananas are said to contain serotonin, but can this boost happiness in whose who eat them? the CNS and cognition through a link known as the gut-brain access. In this case, serotonin in the digestive system may be able to influence mood. . The effects of dietary triptophan on affective disorders. The biochemical link between depression and food addiction between an individual's relationship to food and co-existing mood disorders is. We use food to affect our moods all the time without even thinking about it. .. Journal of affective disorders, 29 (), PMID:
Manipulation of tryptophan levels, acutely or chronically, by depletion or supplementation, is an experimental procedure for modifying peripheral and central serotonin levels. These studies have allowed us to establish the role of serotonin in higher order brain function in both preclinical and clinical situations and have precipitated the finding that low brain serotonin levels are associated with poor memory and depressed mood.
The gut-brain axis is a bi-directional system between the brain and gastrointestinal tract, linking emotional and cognitive centres of the brain with peripheral functioning of the digestive tract. An influence of gut microbiota on behaviour is becoming increasingly evident, as is the extension to tryptophan and serotonin, producing a possibility that alterations in the gut may be important in the pathophysiology of human central nervous system disorders.
In this review we will discuss the effect of manipulating tryptophan on mood and cognition, and discuss a possible influence of the gut-brain axis. Introduction Tryptophan is an essential amino acid found in many protein-based foods and dietary proteins [ 1 ] including meats, dairy, fruits, and seeds.
High-glycaemic index and -glycaemic load meals also increase the availability of tryptophan [ 2 ]. Levels of plasma tryptophan are determined by a balance between dietary intake [ 3 ], and its removal from the plasma as a part of its essential role in protein biosynthesis [ 4 ].
Aside from its role in protein formation, tryptophan is a precursor for a number of metabolites, most notably kynurenine and the neurotransmitter, serotonin which is the focus of this review.
Serotonin and Kynurenine Tryptophan is the sole precursor of peripherally and centrally produced serotonin [ 4 ]. Kynurenine is the precursor of kynurenic acid, an antagonist at glutamate ionotropic receptors. The role of kynurenine in the brain is beyond the scope of this review.
Serotonin and Its Receptors Serotonin synthesis occurs in the periphery within the gut neurons and enterochromaffin cells and centrally within the neurons of the raphe in the brain stem. The effects of tryptophan depletion on peripheral serotonin production will be discussed later. For central serotonin production to occur, tryptophan first needs to gain access to the central nervous system CNS via the blood-brain barrier.
Tryptophan is a substrate for the large neutral amino-acid transporter system and competes for transport with several other amino acids essential for brain function.
This competition for transport is the basis for some acute tryptophan depletion diets e. It is generally accepted that most of our tryptophan is bound to plasma albumin and hence is unavailable for transport into the brain.
This normally limits the tryptophan available for central serotonin synthesis but release of tryptophan from this pool could increase transport. In addition to free tryptophan levels, findings from exercise studies demonstrate that there must be other, currently unknown, mechanisms controlling central uptake of tryptophan [ 11 ].
Once in the CNS, l-tryptophan is hydroxylated to 5-hydroxytryptophan by the enzyme tryptophan hydroxylase type 2, the rate limiting step in brain serotonin synthesis. This is followed by subsequent decarboxylation involving the enzyme l-aromatic acid decarboxylase to serotonin 5-hydroxytryptamine, 5-HT.
Serotonin is then taken up into vesicles by the vesicular monoamine transporter isoform 2 of the raphe neurons.
Degradation of serotonin is via monoamine oxidase type A and aldehyde dehydrogenase to the major serotonin metabolite 5-hydroxyindoleacetic acid 5HIAA. Levels of serotonin are also influenced by the tryptophan-degrading enzyme, indoleamine 2,3-dioxygenase and tetrahydrobiopterin, the cofactor of tryptophan hydroxylase.
All but one subtype of the many serotonin receptors are metabotropic G protein—coupled receptors. Multiple serotonin receptors have been found, with receptor families from 5-HT1 to 5-HT7 [ 1213 ]. The 5-HT3 receptor is unique among the currently known serotonergic receptor subtypes in that it belongs to the ionotropic, ligand-gated ion channel family.
Serotonergic neurons innervate large areas of the human brain, with most projections arising from neuronal cell bodies in the dorsal and median raphe and neighbouring nuclei of the lower brain stem.
There are projections to the hippocampus, amygdala, hypothalamus, thalamus, neocortex, and basal ganglia, although most structures receive some serotonergic innervation [ 14 ]. Through this diffuse network within the central nervous system, serotonin modulates a wide array of functions including sleep, control of appetite and temperature, and the focus of this review, mood and cognition.
The mechanism of these medications is believed to be in part by increasing synaptic levels of monoamines, mainly serotonin and noradrenaline and subsequent activation of serotoninergic and noradrenergic postsynaptic and autoreceptors [ 17 ]. The therapeutic benefits of increased levels of monoamines were discovered in the middle of last century, when monoamine oxidase inhibitors and tricyclic antidepressants showed efficacy in treating depression.
This led to the monoamine hypothesis where depression was thought to be caused by a deficiency in monoamine neurotransmitters [ 18 ]. The effect of serotonin on mood has been investigated using an acute tryptophan depletion technique where lowering dietary tryptophan levels causes a lowering of brain serotonin levels, allowing analysis of serotonin-dependent behaviour [ 23 ].
One of the most important vitamins key to serotonin function is thiamine, one of the components of Vitamin B Complex. Simply altering the levels of thiamine in our diets and ensuring enough intake can have amazing effects. Another Vitamin-B compound, folic acid, is also strongly linked with serotonin levels. Boosting folate levels in older people, who are generally deficient compared to younger adults, has been found to improve their mood and cognitive function.
Food and mood: relationship between food, serotonin and affective disorders.
Even in healthy adults higher levels of serum folate have been linked to fewer mood swings and negative moods. And even more impressively, high folate levels can improve other depression treatments, particularly with how well anti-depressants work. Exactly how folate relates to serotonin is unclear, though it appears to act through an intermediate compound called S-adenosylmethionine SAM.
SAM increases serotonin levels, but it requires folic acid. Folic acid deficiency leads to low levels of SAM, and subsequently reduced serotonin. Serotonin and Behavior One way in which we can help our bodies have healthy serotonin levels is by good behavior.
Things we do, behaviorally, have a major impact on serotonin levels. For example, stressing, feeding, and exercise have been shown to have marked affects on serotonin levels in rats. It turns out that sleep and exercise are particularly strongly tied to serotonin. One way in which this occurs is by increasing serotonin. Exercise is a cheap and dirty way to boost blood and brain serotonin levels immediatelymaking it a good alternative to other ways of dealing with stress and depression.
But exercise does even more: Increased levels of exercise have been shown to increase neuron productiongiving out brains better ability to utilize the serotonin boosts and improve our moods.
Exercise also allows our brains cells to function better by making them more flexibleleading to better responses to all neurotransmitters, including serotonin. Sleep, however, is even more important when it comes to serotonin. People have been studying the connection between serotonin and sleeping behaviors for over 50 years.
The Connection between Food and Mood - WholeBody Solutions
We know that changes in serotonin levels have marked impact on sleeping, with decreases in serotonin leading to apnea or other sleep problems. But only recently have we realized the opposite is true, too. Lack of sleeping negatively affects our brains neuronal signalingincluding how it responds to serotonin.
This means that consistent healthy sleeping patterns are key to maintaining healthy serotonin signaling in our brains and likely our bodies in general. Go Outside and Be Happy! Another, simple way to increase serotonin production is to get outside.
Scientists discovered the connection between light and serotonin almost accidentally. They looked at levels of serotonin in recently-dead people, and found higher concentrations of serotonin in those who died in the summer instead of the winter. That got doctors thinking. It was already known that many people have seasonal changes in mood, with more depression occurring during the cold, dark winter than the warm, sunny summer. It had even been found that increasing light levels helped treat non-seasonal depression.
Could light be having an impact on serotonin levels? Taken together, these suggest that a walk in the sun or getting away on vacation to somewhere tropical and sunny during the darker months might be able to naturally boost serotonin levels. There are other behavioral ways to change serotonin levels, too. Rising evidence suggests that our own emotions and moods affect serotonin levels. In other words, trying to boost our moods or rosy our outlooks can help raise serotonin levels.
Things you can try: Meditation Talking to Friends Counseling All these mood-boosting behaviors might just help raise overall serotonin levels, allowing us to keep out of those bad moods later on. Over-eating of carbohydrates and sugars can lead to decreased sensitivity to serotonin, leading to negative mood and physical side effects like obesity. Eating lots of protein can help balance serotonin levels. As it turns out, eating protein before carbs curbs the usual spike in serotonin.
And, the truth is, we want to cut down our serotonin sometimes. It is a mild sedative, and eating serotonin-boosting foods in the middle of the day can make us drowsy and less focused. A protein-rich snack instead will help increase energy and keep you going when you need it most. Even worse, eating too serotonin-boosting foods, while it might feel good for a short time, can lead to a worse crash later on.
The scientific name for serotonin is 5-hydroxytryptamine, or 5-HT. It is mainly found in the brain, bowels, and blood platelets. Serotonin is used to transmit messages between nerve cells, it is thought to be active in constricting smooth muscles, and it contributes to wellbeing and happiness, among other things. As the precursor for melatonin, it helps regulate the body's sleep-wake cycles and the internal clock.
Serotonin: Facts, uses, SSRIs, and sources
It is thought to play a role in appetite, the emotions, and motor, cognitive, and autonomic functions. However, it is not known exactly if serotonin affects these directly, or if it has an overall role in co-ordinating the nervous system. It appears to play a key role in maintaining mood balance. Low serotonin levels have been linked to depression.
Fast facts on serotonin Serotonin is an important chemical and neurotransmitter in the human body. It is believed to help regulate mood and social behavior, appetite and digestion, sleep, memory, and sexual desire and function.
There may be a link between serotonin and depression. If so, it is unclear whether low serotonin levels contribute to depression, or if depression causes a fall in serotonin levels.
Drugs that alter serotonin levels are used to treat depression, nausea, and migraineand they may have a role in obesity and Parkinson's disease. Other ways to increase body serotonin levels may include mood induction, light, exercise, and diet. Can serotonin boost happiness, or is it more complex than that? Serotonin is created by a biochemical conversion process that combines tryptophan, a component of proteins, with tryptophan hydroxylase, a chemical reactor.