Gut-brain axis important to mental health

Gut health is a food and beverage megatrend. Currently valued at $51.62bn globally, and projected to grow at a CAGR of 8.3% over the next five years (Grand View Research), it’s taking the industry by storm and shows no sign of stopping.

In fact it’s gaining strength, with consumer interest in gut health leading to a 370% rise in gut-health related internet searches over the past year alone (Biotiful Gut Health).

“Consumers are now understanding not just that gut health is important, but also the many ways that gut health can impact other areas of health and wellbeing, from digestive issues, mental health, sleep, skin health, and even weight loss,” says Natasha Bowes, founder and CEO of Biotiful Gut Health.

Recently, researchers from Duke-NUS Medical School and the National Neuroscience Institute, found evidence of the role gut microbes play in controlling anxiety.

How do gut microbes affect anxiety?

Scientists from Duke-NUS Medical School and the National Neuroscience Institute have identified a significant link between gut microbes and anxiety-related behaviour. Their newly published study reveals that microbial metabolites – specifically indoles – directly influence brain activity associated with anxiety. This discovery, they say, opens the door to potential probiotic-based treatments that could support mental health.

In preclinical studies, the scientists observed that in a germ-free environment, those which were not exposed to live microbes, showed significantly more anxiety-related behaviour than those with typical resident live microbes.

Further investigation revealed the increased anxiety was associated with heightened activity in the part of the brain, which processes emotions such as fear and anxiety – the basolateral amygdala (BLA).

This was identified to be related to specialised proteins within brain cells, known as the calcium-dependent SK2 channels. These channels are associated with anxiety behaviour. In conditions when the body and brain are exposed to live microbe metabolites, the SK2 channels prevent neurons from becoming overly excited and firing too frequently.

“Our findings reveal the specific and intricate neural process that links microbes to mental health,” says Shawn Je, associate professor at Duke-NUS’ Neuroscience and Behavioural Disorders Programme. “Those without any live microbes showed higher levels of anxious behaviour than those with live bacteria. Essentially, the lack of these microbes disrupted the way their brains functioned, particularly in areas that control fear and anxiety, leading to anxious behaviour.”

To better understand the role of microbes in this process, the research team introduced live microbes into germ-free mice. This was found to reduce the elevated neuronal activity in SK2 channel activity. As a result, the mice displayed significantly less anxiety-related behaviour – their emotional responses became like those exposed to microbes.

“Our findings underscore the deep evolutionary links between microbes, nutrition, and brain function,” says Professor Patrick Tan, Senior Vice-Dean for Research at Duke-NUS. This has huge potential for people suffering from stress-related conditions, such as sleep disorders or those unable to tolerate standard psychiatric medications. It’s a reminder that mental health is not just in the brain–it’s in the gut too.”

What does these findings mean for food and beverage?

The gut health trend is proving revolutionary for the food and beverage industry. It’s fuelling innovation and new product development, and supercharging sales.

“Over the last ten years the patents and filings related to food and drink with probiotics added to them has just soared,” says Rick Miller, associate director for specialised nutrition at market research firm Mintel. “We’ve seen an exponential growth of probiotic infused products.”

What’s more, brands and retailers are pushing the conversation further by helping to educate consumers on gut health, and making products easily available to them.

“Our current ‘Gut Health Reset‘ campaign is aimed at educating consumers on the benefits that gut health can have in improving overall health and wellbeing, and on specific areas such as digestive health, mood, weight loss, immunity and muscle gain,” says Biotiful Gut Health’s Bowes. “And we’re now seeing an increasing number of retailers establish dedicated gut health / kefir bays in store.”

But which products are likely to be most successful in the future?

“We believe fermented foods – kimchi, sauerkraut and kefir – will continue to grow in popularity,” says Bowes.

However sales of other foods, not directly associated with gut health are also projected to thrive in the future.

Source: Microbial metabolites tune amygdala neuronal hyperexcitability and anxiety-linked behaviors

Published online: 5 February 2025

DOI: 10.1038/s44321-024-00179-y

Authors: Weonjin Yu, Yixin Xiao, Anusha Jayaraman et al.