If you want to improve how you feel, get a better night’s sleep and boost your libido, it could be as simple as increasing your serotonin levels.  Here's what you need to know about this important chemical...
what is serotonin?
You may have heard of serotonin before, but little do you realise this powerful chemical has been active in your body for your entire life. It is predominantly found in the brain, the central nervous system, and the bowels and works as a neurotransmitter to carry signals along and between nerves. Serotonin is produced as part of a chemical reaction between tryptophan, which enters the neurons, an enzyme called tryptophan hydroxylase, which produces 5-HTP, and an aromatic L-amino acid called decarboxylase, which works together with 5-HTP to make serotonin. This is then stored within the brain’s synaptic vesicles and gets held at the nerve terminals, where it waits for the body to call on its release. Once needed, it is then activated. 
what does serotonin do?
Serotonin was first discovered in 1948 by Maurice M. Rapport, and is thought to hold a number of functions. Most notably is its impact on the brain. It is widely understood that being deficient in serotonin can lead to depression and an overall decline in health and happiness.  Serotonin (5-ht) is produced as part of a chemical reaction between tryptophan, which enters the neurons, an enzyme called tryptophan hydroxylase, which produces 5-HTP, and an aromatic L-amino acid. Essentially, serotonin provides balance to our moods. Research has also found connections between serotonin and appetite and digestion, sexual desire and function, people's ability to sleep, memory, and social behaviour. This all comes from its influence in the brain.
where is serotonin produced?
While serotonin is an important neurotransmitter in the brain and given that many people associate their mood with the mind, the majority of serotonin - between 80% and 90% - lives in the gastrointestinal tract. It is manufactured both here and in the brain. However, like dopamine, serotonin is unable to cross between the blood - brain barrier, and therefore only serotonin produced by the brain can be used by the brain. 
how can we boost serotonin?
An effective way to increase serotonin is supplementing your diet with micronutrient 5-htp . It's the building block to your chemical messenger serotonin (5-ht)
It works to boost your mood by increasing the amount of serotonin in the brain, which is thought to in turn improve the way your brain processes emotions and regulates sleep . In a study of people experiencing stress from relationships (such as going through a break-up) 5-htp appeared to help them with their psychological symptoms by boosting their serotonin levels .
A study by Simon Young in 2007 supports the idea of bright light exposure helping – although the research supporting this is indirect. It has been found that people who die in summer have higher serotonin levels than those who die in winter.  He also suggests that exercise could raise brain serotonin. Exercise has been found to have antidepressant and anxiety-relieving effects. Additionally, diet can play a key role. Certain foods like for example soy beans, tofu, salmon, tuna fish, beef, turkey and other meats that contain purified tryptophan can increase brain serotonin.
Interestingly, a study that was conducted on roundworm found that when feeding them familiar food, this activates neurons in the brain which subsequently leads to the release of serotonin. Although further studies are needed to show this process in humans, it could explain why eating our favourite meals or comfort foods serve to improve our mood so much. 
Although illegal and not advised, research has also found that drugs such as LSD and Ecstasy cause a surge in serotonin levels - this is most likely why they are seen by many as being mood-elevating. 10] It should be noted that high serotonin levels are not always something we want to have in high doses though, as serotonin can be linked with nausea.