Gotu Kola – a natural calmer

13th June 2016
Beryl Shuttleworth
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Have you heard of the neurotransmitter called Gamma Amino Butyric Acid  (GABA)? GABA is the main inhibitory neurotransmitter. This means that, in mammals, it reduces neuronal excitability throughout the nervous system.

You might have heard GABA marketed as a human calming supplement, taken by mouth. This is absolute nonsense. GABA, if taken by mouth, doesn’t cross the blood brain barrier (the ‘wall’ between the brain and the rest of the body). So, it never gets into the area of the body where it can have an effect. This is true for all mammals.

Gotu Kola and GABA

This is where the herb, Gotu kola (aka Centella asiatica) is useful. Gotu kola has been found to significantly (over 40%) stimulate the enzyme Glutamate decarboxylase (GAD). GAD’s job is to make GABA. So, by stimulating GAD activity, we increase GABA in the brain, where it is needed.

Researchers attempted to test a practical symptom of anxiety – the startle response to noise. Their thinking was that anxious people tended to become startled more easily. In a double-blind, placebo-controlled trial, 40 human participants were given either Gotu kola or placebo and then subjected to sudden loud noises. Researchers measured eye blinks and found a significantly reduced startle response in those treated with Gotu kola.

I know that I don’t need to tell horse people how significant the “startle response” is in anxious horses. Also, horses (unfortunately) don’t restrict their startle response to eye blinks!!! They are world leaders in startle response….

When taken orally, Gotu kola seldom causes any side effects other than the occasional allergic skin rash, and safety studies suggest that it is essentially non-toxic. Studies in rabbits have shown it to be safe in pregnancy. It is on the FDA’s GRAS (generally recognised as safe) list.



  • Effects of traditionally used anxiolytic botanicals on enzymes of the γ-aminobutyric acid (GABA) system, Canadian Journal of Physiology and Pharmacology, 2007, 85(9): 933-942, 10.1139/Y07-083 (
  • Bradwejn J, Zhou Y, Koszycki D, et al. A double-blind, placebo-controlled study on the effects of Gotu Kola (Centella asiatica) on acoustic startle response in healthy subjects. J Clin Psychopharmacol. 2000;20:680-684.
  • Kartnig T. Clinical applications of Centella asiatica (L.). Herbs Spices Med Plants. 1988;3:145-173.
  • Bosse JP, Papillon J, Frenette G, et al. Clinical study of a new antikeloid agent. Ann Plast Surg. 1979;3:13-21.

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