Of course, this impact on sleep is an indirect one – fermented foods benefit gut health, which, in turn, benefits sleep. It’s for this reason that Dr Sammie Gill, a registered dietitian for Symprove, warns against relying on fermented foods to improve sleep: not only are there over 5,000 types of fermented foods with varying nutritional profiles, but not all fermented foods contain probiotics, so the benefits you experience will depend on the individual scenario.

“Probiotics and fermented foods are distinct categories,” she explains. “Probiotics are targeted towards health conditions and have a specific World Health Organisation definition – ‘live micro-organisms which when administered in adequate amounts confer a health benefit on the host’.

“Fermented foods may or may not contain live microbes, and if they do, that doesn’t mean they are probiotic microbes. The bacteria in fermented foods are often loosely defined and not always live (eg baking sourdough kills the microbes).”

That doesn’t mean fermented foods can’t have a beneficial influence on your gut health – whether or not they contain probiotic microbes, many fermented foods are a good source of prebiotics (foods that act as food for gut microflora) and fibre.

Can eating more fermented foods benefit your sleep? We asked the experts