1. Serotonin is a “happy chemical”, necessary for sleep, digestion, bone health, mood regulation, and wound healing.  
2. Key nutrients such as SAMe and B6 can help increase the synthesis of serotonin.
3. Movement is crucial to serotonin production as it increases tryptophan which is a precursor to serotonin.  
4. Optimising serotonin levels daily will ensure mood stability and the health of your mind and body.

Serotonin is a neurotransmitter with a wide array of physiological functions. It’s often referred to as the ‘happy chemical’.

What Is Serotonin?

Serotonin (5-hydroxytryptamine) is a chemical messenger that functions both as a neurotransmitter and as a hormone. Serotonin produced in the brain acts as a neurotransmitter and modulates a range of functions such as mood, appetite, sleep, learning, and memory. Gut-derived serotonin acts as a hormone and regulates intestinal functions. Intriguingly, up to 90% of serotonin is produced in the gut! Serotonin is also bound to platelets and plays a role in vasoconstriction and blood clotting.

Serotonin is made from tryptophan, an essential amino acid that can not be synthesised by the body and must be supplied by the diet; it is found in most protein-rich foods such as eggs, turkey, and nuts.

What Does Serotonin Do?

Serotonin regulates a wide range of physiological and psychological processes:

• supporting sleep and circadian rhythm
• digestive processes
• reducing depression and anxiety
• stabilising mood 
• healing wounds
• maintaining bone density

Here is a closer look at serotonin’s many functions.

• Sleep

Serotonin is a precursor to melatonin, a  hormone that helps to regulate the circadian rhythm—the internal “body clock” that controls your sleep-wake cycle.

Serotonin is converted to melatonin in the pineal gland, the most serotonin-rich tissue in the body. The synthesis and release of melatonin are stimulated by darkness and inhibited by light.  

Another, quite unexpected regulator of the conversion process is the stress hormone noradrenaline (3). It is well documented that individuals with adrenal fatigue may not be producing sufficient levels of melatonin due to low levels of noradrenaline, which in turn impacts their sleep quality (4). 

• Digestion

Serotonin has been linked with gut functions like assimilation and absorption of nutrients, alongside the regulation of gut motility. The hormone also plays a protective role in the gut (5). For example,  serotonin production can spike in response to an irritant in order to promote swift elimination of the toxins of the body. 

Serotonin deficiency is found to be a prominent factor in the prevalence of gut diseases like irritable bowel syndrome (IBS). 

• Depression, Anxiety, and Mood Regulation

Serotonin is considered to be a natural mood stabiliser and, when functioning normally, it helps people with feeling happy, calm, focused, and emotionally stable. Serotonin can also regulate anxiety and reduce feelings of depression. 

It is important to note that serotonin does not work in isolation and relies on other neurotransmitters such as dopamine and acetylcholine to support a healthy mood. 

Interestingly, increased inflammatory markers have been linked to lower tryptophan levels, decreased brain serotonin activity, and depression.

• Wound Healing and Cardiovascular Health 

Blood platelets release serotonin to help heal wounds after an injury occurs. Serotonin causes vasoconstriction (narrowing) of the tiny blood vessels, slowing blood flow and helping form blood clots. This procoagulant activity of serotonin has been associated with an increased risk of cardiovascular events.

• Bone Health

Serotonin is important for bone health, influencing the balance between bone formation and resorption. Reducing levels of gut serotonin may help treat osteoporosis—a condition that reduces bone strength and increases the risk of fractures. 

Symptoms of Lowered Serotonin Activity

Sufficient levels of serotonin will make you feel calm, easy-going, positive, confident, and mentally flexible. 

If your serotonin levels are low, you might be on the other side of the spectrum: 

• feeling anxious, low, panicky, or depressed
• having low self-esteem
• experiencing poor memory
• having sleep issues or feeling fatigued
• feeling impulsive or aggressive 
• having a decreased appetite
• experiencing  nausea and digestive issues
• craving sweets and starchy foods
• not enjoying friendships and relationships

What Contributes To Serotonin Deficiency?

Many lifestyle factors can lead to serotonin imbalances:

• A poor diet lacks the nutrients and cofactors required to build serotonin.
• Digestive issues such as gut inflammation, infections, and leaky gut can impair serotonin production.
• Toxic substances such as chemicals, pesticides, and some prescription drugs can permanently damage the nerve cells that make serotonin.
• Certain substances such as caffeine, alcohol, nicotine, sweeteners, antidepressants, and some cholesterol-lowering medications deplete serotonin and other neurotransmitter levels.
• Hormone changes can cause low levels of serotonin and neurotransmitter imbalances. Oestrogen deficiencies associated with post-menopause can impact serotonin levels and activity due to the oestrogen-serotonin relationship.
• Lack of sunlight. Serotonin production in the brain requires adequate light exposure. This may explain why during winter,  on cloudy days or when spending lots of time indoors symptoms of low mood and depression can set in.  
• Chronic stress. Low cortisol can hinder the conversion of serotonin to melatonin and cause difficulty sleeping. 
• Genetic factors.

What Is The Normal Range For Serotonin?

Generally, the normal range for blood serotonin levels is 101–283 nanograms per millilitre (ng/mL). This benchmark can differ depending on the measurements and samples being tested.

Functional pathology testing can measure serotonin levels in urine with increased accuracy. 

It cannot be overrated how important it is to objectively assess and treat mood disorders for symptomatic relief and improved quality of life. 

How Can We Increase Serotonin Naturally?

Nutrition

You can’t directly get serotonin from food, but as discussed earlier you can get its precursor, tryptophan. Tryptophan is an amino acid found primarily in high-protein foods such as:

• eggs
• turkey and other poultry
• nuts and seeds
• salmon
• cheese and milk
• whole grains
• banana
• seaweed.

Studies have shown that tryptophan in the diet is linked to brain serotonin levels, with lower amounts of dietary tryptophan causing brain serotonin levels to drop.

The availability of tryptophan for the production of serotonin in the brain will depend on the health of the digestive function and the activity of the blood-brain barrier transport system. 

The digestive system needs to be breaking down and absorbing nutrients effectively to supply sufficient amounts of tryptophan to the brain. Then tryptophan must be transported across the blood-brain barrier by a carrier protein and this process is tightly regulated, controlling the amount of serotonin that can be made. 

The production of serotonin is reliant on sufficient levels of nutrients, especially iron, magnesium, vitamin D and methyl donors such as B12 and B6. Studies have shown that the consumption of tryptophan and B6 combined supports the greater synthesis of serotonin and better sleep quality.

Research suggests that eating carbs along with foods high in tryptophan may help make tryptophan more available to the brain. For example, you combine turkey with brown rice or oats with a handful of nuts.

In general, eating a nutrient-dense diet offers a range of health benefits and boosts overall wellbeing.

Supplements

Some dietary supplements may help to boost the production and release of serotonin.

• SAMe (S-adenosyl-L-methionine)

SAMe appears to help increase serotonin and may improve depression symptoms, but don’t combine it with any other supplements or medications that increase serotonin, including certain antidepressants and antipsychotics.

• Probiotics

Your gut-brain axis connects the central nervous system to the gastrointestinal tract. Research suggests that consuming more probiotics may increase serum tryptophan levels. It is recommended to increase probiotic-rich foods such as yogurt, and fermented foods, such as kimchi, tempeh, miso or sauerkraut, or take probiotic supplements, such as Saccharomyces boulardii (SB) which may have a more powerful result.

• Vitamin B6 (bio-activated Pyridoxal 5’-phosphate)

B6 is an important cofactor for the production of serotonin from tryptophan. 

Once our body breaks down the food to retrieve tryptophan, it must then also have available a bio-activated form of B6 in order to further produce serotonin. 

• 5-HTP

This supplement may be effective for increasing serotonin. A small 2013 study suggests it worked as effectively as antidepressants for those with early symptoms of depression.

• BacoMind® – Bacopa monnieri (organic)

BacoMind® is a patented extract of Bacopa monnieri, clinically validated to enhance memory and cognition. It’s an antagonist of serotonin receptors 5-HT2A and 5-HT6, known to influence neurological pathways associated with cognition.  

• Sunshine

Exposure to sunshine is associated with an increase in serotonin levels. Sunlight cues special areas in the retina of your eyes, which triggers the release of serotonin. Your skin may also be able to synthesise serotonin. 

To optimise the benefits of sunshine, aim to spend at least 15 minutes outside each day with your arms uncovered (make sure to follow safe sun guidelines). This will boost your vitamin D levels too, an important co-factor for serotonin synthesis. 

Vitamin D deficiency is common in Australia with over 30% of adults having a mild, moderate, or even severe deficiency.

If you live in a cooler climate, spend a lot of time indoors, or have a high risk for skin cancer, you can still increase serotonin levels with bright light exposure from a light therapy box. .

• Aerobic Exercise

Exercise releases tryptophan into the blood and decreases the number of other amino acids—helping tryptophan cross the blood-brain barrier. The goal is to participate in any exercise which increases your heart rate. Find something you enjoy, such as:

• dancing
• tennis
• jogging
• cycling
• boxing
• or swimming.

Research conducted at the University of Texas at Austin found that just a single 40-minute period of exercise can have an immediate effect on mood.

Takeaway

Serotonin influences every part of your body, including many important day-to-day functions. If your serotonin levels are out of balance, it can affect your emotional, mental and physical well-being. Always talk to your health provider if you have any concerns.