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How Diet and Lifestyle Deplete Serotonin and GABA: Undernourished and Overstimulated


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.[1]

Tryptophan, as well as all other large neutral amino acids, are transported across the blood brain barrier (BBB) by the LNAA transporter protein.[2],[3] Tryptophan must compete with other amino acids, such as leucine, valine, phenylalanine, and tyrosine, for transport into the brain.[4] 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.[5] 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.[6] 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.[7] 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.[8]

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.[9] 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.[10] 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.[11]

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.[12] 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.[13] Studies have also shown significant reduction in serotonin levels in the brain in response to stress.[14] Increased cortisol levels induced by stress reduce serotonergic signalling, and serotonin receptors are also down regulated in the hippocampus and cortex after prolonged stress.[15],[16]

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.

Find a provider to assess your serotonin and GABA levels to determine if precursor support could help you relax or become a provider.


[1] Toker L, Amar S, Bersudsky Y, et. al. (2010). The Biology of Tryptophan Depletion and Mood Disorders. Israel Journal of Psychiatry & Related Sciences, 47,1, 46-55.

[2] Ibid.

[3] Fernstrom JD. (2013). Large neutral amino acids: dietary effects on brain neurochemistry and function. Amino Acids, 45,419–430.

[4] Toker et. al. op. cit., Fernstrom op. cit.

[5] Toker et. al. op. cit.

[6] Ibid.

[7] Fernstrom op. cit.

[8] Ibid.

[9] Ibid.

[10] Ibid.

[11] Ibid.

[12] Kumar A, Rinwa P, Kaur G, et. al. (2013). Stress: Neurobiology, consequences and management. Journal of Pharmacy and Bioallied Sciences

[13] Ibid.

[14] Ibid.

[15] Kumar et. al. op. cit.

[16] 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.

Connie Shoemaker, ND

Connie Shoemaker, ND

“Educating Sanesco’s clients is the culmination of a life’s work.” Beginning when she left the hospital environment to manage a functional laboratory, Genova Diagnostics (formerly Great Smokies Laboratories) in 1987, Dr. Connie Shoemaker has continued to increase her knowledge of herbs and biochemistry as a journey of love. With her bachelor’s in science from Western Carolina University, she had worked in hospital laboratories for the first twelve years of her career. Then, personal health challenges led her to discover a new approach to her health and a determination to share it with others. In 1991, she began teaching and educating innovative practitioners in the U.S. and internationally as a manager of marketing, sales, and customer service.

The addition of her Doctor of Naturopathy degree to her existing knowledge base expanded her knowledge and her respect for a more natural approach to healing through balance. At Sanesco, she initially served to oversee technical development of products and services.

Now, she educates Sanesco’s clients on application of the CSM™ model for their specific patients and how to integrate the CSM™ model with other modalities they offer in their practice. In her personal life, Connie educates private clients on various health topics.

Disclaimer: The information provided is only intended to be general educational information to the public. It does not constitute medical advice. If you have specific questions about any medical matter or if you are suffering from any medical condition, you should consult your doctor or other professional healthcare provider.

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Inhibitory Neurotransmitter


One of our feel-good neurotransmitters; Low levels of serotonin may relate to occasional symptoms like moodiness, sleep issues, and carb cravings. 

Learn why and how to test serotonin levels