In the Sanesco Clinical Department, one of the most common patterns of neurotransmitter imbalances we see is low levels of serotonin and GABA.
Serotonin and GABA are part of the inhibitory system that relaxes the body and promotes good mood. They also prevent over-excitation by modulating the excitatory neurotransmitters such as dopamine, norepinephrine, and epinephrine. The inhibitory neurotransmitters are often depleted more quickly than excitatory neurotransmitters. Why is this such a common pattern? Let’s take a look at how the inhibitory system is affected by diet and lifestyle.
The Impact of Diet on Serotonin and GABA
Particular amino acids are the building blocks to most of our important neurotransmitters. Changes in the concentration of amino acid precursors can affect the concentration of neurotransmitters. Tryptophan is the only amino acid precursor to serotonin.
Tryptophan, as well as all other large neutral amino acids, are transported across the blood brain barrier (BBB) by the LNAA transporter protein., Tryptophan must compete with other amino acids, such as leucine, valine, phenylalanine, and tyrosine, for transport into the brain. Thus, the concentration of tryptophan in the brain that can be used to synthesize serotonin is dependent on the ratio of tryptophan to other large neutral amino acids. Studies have found tryptophan to be particularly sensitive to diet in ways that other amino acids are not.
Tryptophan is the rarest amino acid found in proteins. Researchers tested the effects of consuming different types of proteins on the concentration of amino acids in the blood, and the synthesis of their resulting neurotransmitters in rats. The experimental rats were fed soy protein, casein (phosophoproteins commonly found in mammalian milk), lactalalbumin (a protein or mixture of similar proteins occurring in milk), zein (the major storage protein of corn), and gluten. The researchers found large variation in serum tryptophan concentration and serotonin synthesis, depending on the type of protein eaten. Diets rich in zein, a tryptophan-poor protein, led to much lower serotonin synthesis than lactalalbumin, a tryptophan-rich protein.
Tyrosine is the amino acid precursor to the catecholamine neurotransmitters (dopamine, norepinephrine, epinephrine). The researchers were surprised to find that the same differences in the types of proteins fed to the rats caused very minimal differences in tyrosine concentrations. It is clear that serotonin synthesis is affected by diet in ways that catecholamine synthesis is not.
Serotonin is also affected by diet through the consumption of carbohydrates. When carbohydrates are consumed, insulin is released. Insulin sends amino acids in the blood stream to muscle cells. However, tryptophan is bound to albumin and is therefore unaffected by insulin. The ratio of tryptophan to other amino acids in the bloodstream then increases. Therefore, brain tryptophan concentration and serotonin synthesis is increased in the short term.
Carbohydrates boost the serotonin in our brains, making us feel good. This explains why we crave sweets when we are feeling down. However, this is merely a short-term solution to low serotonin, and the consumption of large quantities of carbohydrates can lead to many health issues, such as weight gain and blood sugar dysregulation.
The Impact of Lifestyle on Serotonin and GABA
Another important cause of serotonin and GABA depletion is the stress of our modern lifestyle. In our society, everyone is expected to work as hard as possible to achieve money and status. This leads to diets rich in processed foods, lack of sleep, and the consumption of drugs and other stimulants, all of which lead to stress! Our bodies are constantly bombarded with emotional and physical stress.
During a stress response, the hormone cortisol and the neurotransmitters norepinephrine and epinephrine are released. This a part of our ancestors’ fight or flight response, which allowed ancient humans to escape life-threatening events, such as an attack from an animal. However, stress caused by the modern American life style is not quite so adaptive.
Stress has been shown to alter GABA signalling and lower GABA levels in some areas of the brain. Studies have also shown significant reduction in serotonin levels in the brain in response to stress. Increased cortisol levels induced by stress reduce serotonergic signalling, and serotonin receptors are also down regulated in the hippocampus and cortex after prolonged stress.,
So we see that it is not only our diets but our frenzied lifestyle that contributes to the depletion of our inhibitory neurotransmitters. Supplementing precursor amino acids can go a long way to overcoming this problem, allowing us to live our life in a more relaxed manner.
 Fernstrom JD. (2013). Large neutral amino acids: dietary effects on brain neurochemistry and function. Amino Acids, 45,419–430.
 Toker et. al. op. cit., Fernstrom op. cit.
 Toker et. al. op. cit.
 Fernstrom op. cit.
 Kumar A, Rinwa P, Kaur G, et. al. (2013). Stress: Neurobiology, consequences and management. Journal of Pharmacy and Bioallied Sciences
 Kumar et. al. op. cit.
 Tafet GE, Idoyaga-Vargas VP, Abulafia DP, et al. (2001). Correlation between cortisol level and serotonin uptake in patients with chronic stress and depression. Cognitive, Affective, & Behavioral Neuroscience, 1,4, 388-393.