You know that your food affects your health, but did you know it can also affect your mood?
Science has shown us that food is so powerful that it can alter the neurotransmitters like serotonin that shape your feelings. This paper will explain how this happens and how you can eat to be happier.
What does serotonin do?
Serotonin is widely known for its role in mood regulation. As a neurotransmitter, it enables brain cells to send signals back and forth. Those signals are responsible for regulating your moods and promoting healthy sleep. Too little serotonin, for example, can make you sad, crave sweets or even loose your temper.
How do we make it?
Tryptophan (L-Try), an amino acid found in some foods, is needed for the production of serotonin. It’s an essential amino acid, which means our bodies can’t produce it, so we have to get it from our foods. 
Your body makes L-Try into serotonin with the help of several nutrients. The first step, making L-Try into 5 hydroxytryptophan (5HTP) depends on iron, riboflavin, and vitamin B6. Folate is needed to make 5HTP into serotonin. If you are low on any of these nutrients, you may be shortchanging your brain.
Since tryptophan is the only amino acid that can form serotonin, the amount of it in our diet is a decisive factor in the way we respond to stress, as well as the way we develop, adapt to change and age. 
How can serotonin affect us?
The brain-gut axis is “a bidirectional communication system between the central nervous system and the gastrointestinal tract.”  This means that your gut changes your feelings and your feelings change your gut. Serotonin acts on both terminals of this network, and the gut microbiome plays a critical role in regulating the normal functioning of this axis. The powerful influence of gut microbes on tryptophan metabolism and the serotonergic system highlights the importance of diet to maintaining a stable mood and healthy sleep patterns.
The wrong foods can spell trouble for our gut flora, and that, in turn, spells trouble for our moods and our ability to consistently get enough restorative sleep to maintain healthy brain and bodily function.
It also calls into question the benefits of using antibiotics, since the devastating effect on good as well as bad microbes must adversely affect our serotonergic system, and – by extension – our overall well-being.
What happens when you have too little serotonin? Here are some of the common symptoms and diagnosis that go along with it:
Why would it be low?
There are a number of factors that can decrease the amount of serotonin in your body.
Obviously, since our serotonin levels depend on the amount of tryptophan we get in our food, a good place to start is by eating more tryptophan-rich foods.
But first, let’s look at some foods that can lower your serotonin levels.
Which foods lower serotonin?
One more reason to avoid excess fructose – it can prevent you from absorbing tryptophan. As many as 1/3 of us are prone to fructose malabsorption with even the smallest amounts of fructose. If you are among the sensitive, even small amounts of it can be an issue. Even if you’re not sensitive to fructose, too much can block tryptophan for most anyone. 
About one third of the Western European population has fructose malabsorption – the inability to absorb fructose efficiently.  This problem can affect women even more strongly than men. The researchers in this particular study pointed to estrogen as the reason, since estrogen activates an enzyme that alters the metabolism of tryptophan from serotonin (happy) to kynurenic (not happy). It doesn’t help that women have less tryptophan in their bodies than men to begin with, so anything that further decreases the amount of it or alters its metabolism is going to adversely affect their serotonin levels, leading to low serotonin symptoms. 
Alcohol is a psychoactive agent that depresses the central nervous system. Small to moderate amounts of alcohol can increase the amount of serotonin in the body temporarily, which can be a problem for those taking an SSRI, since an additional increase in serotonin puts them at risk of serotonin toxicity syndrome.
Regular use of alcohol causes major disturbances in the metabolism of brain serotonin, decreasing the amount of it in the brain. It also makes the cells respond more poorly to the serotonin that is present. This would explain the link between excessive alcohol use and aggressive behavior, as well as depression and anxiety (or a worsening of those symptoms). 
Diet sodas aren’t an improvement, though. Aspartame’s content is about 50% phenylalanine, which has been shown to deplete serotonin to such an extent, it has been known to trigger manic depression, hallucinations, panic attacks, paranoia, and even suicidal tendencies, as well as other symptoms of low serotonin listed above. The amino acid tyrosine, a product of phenylalanine, “reduces the amount of tryptophan that can cross the blood-brain barrier for utilization in serotonin production.” 
Dopamine is a metabolite of phenylalanine, and altered brain dopamine concentrations have been linked with mental illness, particularly schizophrenia. The direct injection of dopamine into the brain ventricles of humans can induce hallucinations and psychotic episodes. 
Besides phenylalanine, aspartame also contains 40% aspartic acid and 10% methanol. It comes from genetically modified E. coli bacteria. Aspartic acid is an excitotoxin, meaning it goes right to the brain and starts poking it with tiny cattle prods. Methanol is wood alcohol used in antifreeze. 
Considering the bounty of healthier alternatives available, there’s no reason for us to continue poisoning our bodies with chemicals that alter our brain chemistry (for the worse). A fermented drink like kombucha – available in a variety of flavors – will not only refresh you in ways that chemical-laden soft drinks can’t, it will also add beneficial flora to your gut, which in turn can raise serotonin production and help your body heal itself.
I’m wincing as I write this, but even caffeine doesn’t come out squeaky clean under close examination. North Americans who drink caffeinated beverages tend not to stop at the recommended daily limits, and while drinking caffeinated beverages can increase serotonin, excessive caffeine consumption increases the body’s need for the neurotransmitter.
Caffeine increases cortisol levels, in proportion to the amount of caffeine consumed, so while a moderate amount can raise serotonin levels, more than that will raise cortisol levels to the point where your body needs more serotonin to balance the cortisol, since these two neurotransmitters need to remain in balance with each other. 
Your brain adapts to the amount of caffeine you habitually drink, so when you cut back or miss a cup or two one day, the absence or shortfall of caffeine results in a drop in your serotonin levels, which can cause irritability, headache, feelings of anxiousness, and an inability to concentrate. 
According to Medicine Plus, drinking two to four cups of coffee a day isn’t likely to be harmful, but every body is different, and if you’re experiencing frequent headaches, rapid or irregular heartbeat, and difficulty sleeping, you should probably cut back on the caffeine. Too much is unlikely to improve your performance if it sends you to bed with a headache or puts your heart at risk. 
Coffee can also inhibit your body’s absorption of iron, which is a key mineral in the synthesis of both serotonin and dopamine. It can also decrease the circulating amounts of B vitamins, and since we need the activated form of B6 to synthesize serotonin, this can decrease the amount of serotonin produced, while simultaneously creating a greater need for it. 
Which foods raise it?
So, what can you take that will raise the levels of tryptophan – and ultimately serotonin – in your body?
Foods that are naturally higher in tryptophan include the following: 
Foods with L-Try
Food mg of Tryptophan per 100 g
Sesame seeds 882
Sunflower seeds 752
Chia seeds 721
Salmon wild 310
Chicken, white meat 290
Turkey, white meat 290
Turkey, dark meat 280
Black beans 260
Salmon canned 250
Beef ribeye 230
Chicken, dark meat 210
Adzuki beans 190
Beef tenderloin 170
Beef, ground 90% lean 130
What about turkey?
People have been blaming turkey for their post-Thanksgiving-meal naps and general lethargy, when, in fact, turkey isn’t the culprit. Eating too much food – stuffing yourself – is more likely to be the cause of after-meal sleepiness.
Turkey doesn’t contain substantially more tryptophan than other protein sources. It’s the carbs surrounding the turkey on your plate that give the tryptophan a fighting chance against other amino acids that push it to the back of the line. So, tryptophan is a bit like the skinny kid at school who gets pushed around on the soccer field by the bullies but is a great listener and makes you feel all warm and fuzzy inside. When he buddies up with carbs, though, the bullies get distracted, and tryptophan scores the winning goal. And everybody feels better – for a while, anyway.
Let’s look at this from a more scientific angle. When you eat carbs along with a protein that contains tryptophan, your body produces insulin, which diverts other amino acids to the muscles in your body, but it leaves tryptophan alone, giving it the chance it needs to create more serotonin and act on the brain-gut axis.
For the same reason a plateful of turkey will not guarantee you a jovial mood and a good night’s sleep, a glass of warm milk at bedtime won’t raise the level of tryptophan entering your brain, either. Neither will other foods high in tryptophan, such as walnuts, strawberries, or salmon,  though it’s not difficult to find articles on the internet advising people who are suffering from insomnia to eat and drink more of these foods.
In order for tryptophan to do its job, we need some carbs, and later in the day is the best time to take advantage of insulin’s diversionary tactics. This is one reason I created the system of carb-cycling in the Adrenal Reset Diet.
1/4 cup breakfast
1/2 cup lunch
3/4 cup dinner
Good carbs help because eating high glucose, low fructose complex carbohydrates helps L-try get into your brain. Thank insulin for that, since it encourages the absorption of the branched-chain amino acids (BCAAs) but leaves tryptophan alone to do its job.
Here are some complex carbohydrates and their glucose values. 
Good carbs that help L-Try
Food Glucose value per 100g
Kidney beans 0.23
Navy beans 0.21
Wild rice 0.2
Pinto beans 0.13
Sweet potato 0.57
Too many carbs at one time can make you sleepy, and while that can be an advantage in the evening, that’s pretty much the only time most people want to be sleepy. Late evening or nighttime, at least, is a more appropriate time for it. Plus, since insulin is diverting other amino acids to muscle tissue, your body can take advantage of rest time to build muscle, especially if your workout during the day has made muscle repair necessary.
Can you get too much serotonin?
Yes, but not from foods. This is really just a medication reaction. Serotonin toxicity syndrome typically happens as a result of an accidental overdose of a psychoactive drug that increases the amount of available serotonin. When someone starts a higher dose of an antidepressant, a mild or moderate case of serotonin syndrome may result. Severe cases are rare but possible and require immediate hospitalization.
Taking a tryptophan or a 5-HTP supplement while also taking an SSRI puts you at greater risk of serotonin syndrome, since they raise the level of serotonin in the body at the same time the SSRI is inhibiting its reuptake.
 Paterson DS, Trachtenberg FL, Thompson EG, Belliveau RA, Beggs AH, Darnall R, Chadwick AE, Krous HF, Kinney HC; Trachtenberg; Thompson; Belliveau; Beggs; Darnall; Chadwick; Krous; Kinney (2006). “Multiple serotonergic brainstem abnormalities in sudden infant death syndrome”. JAMA 296 (17): 2124–32