Fermented foods have been around for longer than refrigeration, but recently they have developed a reputation for having numerous health benefits. We find out if that reputation is founded in reality.

By Liz Garton

The popularity of kombucha and other fermented foods, like kefir, kimchi and tempeh, has risen on the back of research which shows gut health is closely linked to general, overall health.

"We carry around about two kilos of bugs, each of us, which is kind of gross, but kind of cool," food and nutrition writer Niki Bezzant told Healthy or Hoax host Stacey Morrison, "Scientists used to think that those bugs were just sitting there benignly. Now what they know is that those bugs are very active and they can do a lot in our bodies and they are actually responsible for a whole lot to do with just about every aspect of our health."

Bezzant said as well as a general health halo, probiotic and fermented foods also have this veneer of ancient, exotic wisdom because they've been used in many, many cultures for thousands of years.

Food is fermented when bacteria or yeast pre-digest it and there are lots of different types of fermented foods.

Dr Megan Rossi is a research fellow at King's College London and the author of Eat Yourself Healthy, a "bit of a bible to gut health."

She said there are essentially three different 'mechanisms' for how fermented foods can be beneficial.

"Some fermented foods actually give us the live microbes, like kombucha," said Rossi, "Some just give off healthy chemicals and some break down other elements of foods we call anti-nutrients, which aren't necessarily dangerous but they reduce our ability to absorb some nutrients."

It is not easy to tell if you have a healthy gut, but there are some clues.

Dr Rossi has come up with a quick questionnaire which is also available on her website, The Gut Health Doctor, to help predict your gut health.

"One of the key ones is, are you having regular gut symptoms like constipation, diarrhea, bloating?"

But Dr Rossi said just because you don't have those symptoms doesn't mean you have good gut health.

"So it's things like, how often are you getting sick? Are you really stressed? How much sleep are you having? Are you following a restrictive diet? Do you have family history of a different disease or are you on medications?

"All of those factors combined really give us a more holistic idea of your gut health," she said…

Go to this episode on rnz.co.nz for more details