In Britain, there’s a growing market for functional drinks in particular. Several of these claim to increase the efficiency of Gaba in the brain. The most famous, Sentia, created by a team led by David Nutt, a professor of neuropsychopharmacology at Imperial College London, is intended to mimic the relaxed feeling we might get after a couple of alcoholic drinks with its blend of plants proven to have an effect on Gaba receptors. Sentia is intended to mimic the initial stage of drunkenness, when we feel relaxed and convivial, but does not lead to the other stages, including euphoria, memory loss and dependency.

Another, Impossibrew, contains ingredients including ashwagandha and l-theanine, an amino acid found in tea that is thought to increase Gaba levels in the brain.

It seems unlikely Britain will follow in Japan’s footsteps by putting Gaba directly into food, but researchers are searching for new compounds which could potentially have a Gaba-activating impact.

But what exactly is Gaba, and is it really possible to boost our levels? Here’s what the science says.

What does Gaba do?

Gaba is made by our bodies and present in other animals, plants and microorganisms. In humans, it’s what we call a neurotransmitter, sending chemical messages in the brain just like serotonin or dopamine. It plays a hugely important role in our central nervous system as the primary inhibitory neurotransmitter, which means it blocks chemical messages and decreases the stimulation of our nerve cells.

In other words, it has a calming and relaxing effect. If brain activity consists of billions of neurons turning on and off, “glutamate, the main excitatory neurotransmitter, is the ‘on’ switch,” says Nutt. “Gaba is the ‘off’ switch.”

Alcohol increases Gaba activity in the brain, leading to a temporary feeling of relaxation and a reduction in anxiety, as do drugs which have a sedative effect, for example benzodiazepines such as Valium. (Conversely, stimulant drugs such as cocaine increase glutamate and lower Gaba.)

However, over time, excessive alcohol consumption can diminish Gaba signalling. The more we drink, the more Gaba goes down, leading to anxiety and potentially to addiction as the receptors need more of the alcohol to provide the same effect.

Gaba is actually made from glutamate and to have a properly functioning brain, a delicate balance must be maintained between the two. Decreased Gaba activity has been linked to conditions such as anxiety disorder, depression, schizophrenia, autism and epilepsy.

While the highest concentration of Gaba is found in the brain, smaller amounts can also be found in organs such as the bladder, heart, lung, ovaries and pancreas, with recent research suggesting it has an important function in regulating insulin and metabolising sugar.

What part does Gaba play in gut health?

Most of us are increasingly aware of the importance of gut health as it links to every aspect of our overall wellbeing, from our immune systems to our moods. Fewer realise the key role Gaba plays in our microbiome, the community of microorganisms within our intestines.

“In the past decade, research has shown that the gut has a lot of Gaba receptors,” says Nutt. These are believed to influence everything from gut motility to the enteric immune system which protects the digestive tract from pathogens, and the prevention of inflammation. “Gaba is fundamental to the effective working of the gut,” he adds.

Research also shows that the level of Gaba activity in our guts is linked to our mental health. A review published in scientific journal Nature has shown a strong link between mental health disorders and dysregulation of the microbiome as a result of low Gaba activity. Conversely, studies have shown that raising Gaba levels in the intestine improved depression-like behaviour and stress hormone levels.

“Gaba is an important modulator of microbiome activity in the gut, and of the gut-brain axis – the two-way communication system between the brain and the gastrointestinal tract,” explains Prof Nutt. In other words, if the gut’s Gaba receptors are working efficiently, our mental wellbeing will be better, too.

The friendly probiotic bacteria Bifidobacterium, Lactobacillus and Bacteroides all produce Gaba in the gut, and also in the brain. This is thought to be the result of the communication between the two organs, and including these in your diet – whether via food or supplements – is likely to be beneficial to both.

Can our diet improve Gaba activity?

Many studies have shown the beneficial effects of Gaba derived from diet, including helping to lower blood pressure, control weight and prevent diabetes. Foods naturally high in Gaba include cruciferous vegetables such as broccoli and kale, sweet potatoes, soybeans, tomatoes, strawberries, mushrooms, germinated rice and tea.

Much higher levels are produced when foods are fermented using lactic acid bacteria, such as kimchi, miso, tempeh, sauerkraut, kefir and certain cheeses. These foods are probiotics, known to boost the diversity of good bacteria in the gut. Nutt says: “There is absolutely no doubt that if you’re looking after your microbiome, your Gaba is going to be working more effectively. Eating more fibre, fruits, vegetables, wholegrains and legumes will all help.”

Vitamin B6, found in foods such as bananas, salmon, chicken, tuna, chickpeas, potatoes and eggs, has also been found to support Gaba production and has a positive impact on our mental wellbeing.

Can we boost our Gaba levels by taking supplements?

No, taking large quantities of Gaba orally is not believed to be effective or bring any particular health benefits. While research has shown that blood Gaba levels are elevated 30 minutes after oral Gaba intake, it doesn’t reach the brain. “Gaba cannot cross the blood-brain barrier,” explains Nutt. Instead, any excess is believed to be broken down by the liver.

Gaba supplements are prohibited for sale in Britain and other European countries because of concern over potential for misuse but are legal in the US and Japan, along with a variety of Gaba-enhanced gummies and foods such as chocolate, cereals and teas.

A 2020 systematic review of 14 studies into the impact of consuming Gaba-rich food or supplements on stress and sleep found “limited evidence for stress and very limited evidence for sleep benefits of oral Gaba intake”.

Instead, supplementing with probiotics is a promising alternative. The probiotics increase Gaba activity in the gut – and, in turn, increase it in the brain. One 2023 study found that of commercially available probiotics, the strain Lactobacillus brevis was the most efficient for Gaba production.