Fermented foods: a genetic survey

The science of fermented foods isn't settled - but a genetic approach found some interesting health effects...
15 June 2020

Interview with 

John Leech, APC Microbiome Ireland


Bottles of kombucha.


The science of fermented foods like kefir isn’t quite settled. Which bacteria are in different fermented foods and drinks? And what do each of these bacteria do? The questions start to multiply. John Leech from APC Microbiome Ireland has been taken a genetic approach into expanding this search - as he told Phil Sansom…

John - Well, we've been exploring a variety of fermented foods. The first project looked at roughly 58 fermented foods from mostly Western Europe or from some other countries too. There's a huge variety of fermented foods, including beer, but we're focused mostly on the ones that will contain live microorganisms at the point of consumption. Foods like milk kefir, sauerkraut, kimchi.

Phil - Does this overlap with what you might buy in a store labeled probiotics?

John - It does a bit, yeah. This is - so a probiotic by the scientific definition is any microorganism when consumed in adequate amounts, confers a health benefit. It's widely believed that fermented foods are a good source of probiotics. Now that's something that we're hoping to explore and to investigate and to find maybe more probiotics in fermented foods.

Phil - Okay. What have you been finding?

John - So we looked at genes in these foods that could potentially give some health benefit to the consumer after eating the food. And it was quite promising across the 58 foods. We compared them to non-fermented foods and these foods had much more of these potentially health promoting genes.

Phil - How can you actually tell whether a gene gives a benefit?

John - We scanned the previous studies on probiotic bacteria - bacteria that have been shown to provide a health benefit. In a scientific sense we have a couple of criteria that will help us class a microorganism as a probiotic. And one of the first things that a bacteria or yeast needs to do in order to be considered probiotic is it needs to survive traveling through your stomach, which is quite a low pH, very acidic environment that will kill most things. Can this microorganisms survive all that? So we look for genes that will allow the microorganism to pass through this hostile environment and actually get to your big intestine. Other genes then will be genes that will allow the microorganisms to actually colonise your gut. So these will be genes that would allow the bacteria possibly to stick to your intestinal walls. And then there are other genes we found in some experiments, genes that allow that particular microorganism to influence the host immune system. This microbiome is extremely important in terms of extracting nutrients from your food. And it's also associated with all sorts of different health conditions, particularly chronic health.

Phil - And the more, the better?

John - We think so, it's early days. I mean, a lot of disease states are associated with lower diversity in your gastrointestinal tract. In general having lots of different species down there seems to be good.

Phil - Okay. What did you find? If you had to design me a menu of the best possible foods, what would it be?

John - Foods that were fermented with a high concentration of sugar. These would be foods like kombucha and water kefir and beet kvass. These foods actually showed the highest potential. And that was surprising to us because generally kefir and other dairy foods, they have a ton of research done on them, and they've shown quite good potential so far. But in our investigations, it was actually sugar foods, which they have a very different type of bacteria in them than dairy foods do. So we were a bit surprised by that, but it leads to an awful lot of interesting research down the line.

Phil - You mentioned one there that I didn't, I've never even heard of. What's that beet thing?

John - Beet kvass is a salty drink. In the case of beet kvass it's made out of beetroot juice with a lot of salt added to it. It's not great tasting, to be honest with you. Personally, I'd eat a lot of sauerkraut and kimchi too. I think variety and diversity is probably the key here, but we'd have to actually see if this potential can be translated into actual results. But from our early explorations of the potential, then yeah things like kombucha and water kefir seem to be, have the most potential so far,

Phil - What's this stuff actually going to do for me?

John - Absolutely no idea yet. There has been quite a few studies into kefir and a couple of human studies on kefir, and that can help with things like cholesterol and hypertension. But by and large, most of these fermented foods don't have human trials. Studying fermented foods is very complicated, like one kefir could be very different to another kefir in terms of its composition. So we don't really know yet is the answer.

Phil - If you've got me drinking all this kombucha, water kefir, I gotta be honest: I feel a bit Gwyneth Paltrow right now.

John - Yeah. This is what we're trying to resolve. And this is why we don't make any strong claims about it because there's an awful lot of things on the internet about kombucha and kefir. You'll often see particularly, with kombucha online, claims about it curing cancer and curing arthritis and curing all of these things and kind of information like that can be dangerous. We're trying to see how much truth is behind this. Now our studies are very early days. We're not investigating each food in such depth, but we're trying to catch up and do all these experiments to validate a lot of these health claims. However I know in the Westernised industrial world, we live in quite a sterile environment. We sterilise our foods either through adding preservatives or by cooking it. So we are exposed to an awful lot less bacteria and yeast in our environment. So there are considerations at the moment, just like you'd be given a daily recommended allowance of certain macro and micronutrients. We are trying to push for a daily allowance of bacteria and fermented foods. Obviously you're going to be a great way, and in a lot of cases, a tasty way to fulfil this kind of recommended daily allowance of microorganisms a day.

Phil - It's a lot better than licking the ground every day.

John - Well, it depends on where you live, I guess!


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