7 gut studies worth knowing this month đ§
From the fibres that bloat far fewer people than you'd think, to the microbes you swap when you kiss.
Even as someone who works in nutrition and microbiome research, itâs difficult staying up to date with all the evidence. Thereâs so much out there, and Iâm constantly keeping my eyes peeled for new research.
Here are the studies that sparked my curiosity this month, and I thought Iâd run through them with you.
Some are novel and fun, while others are more useful.
And a couple looked thrilling until I pulled them apart - Iâll tell you which is which, through the eyes of a nutrition and microbiome researcher.
The icemanâs 5,300-year-old gut
Iâm endlessly fascinated that microbes were here long before us, we didnât just pick them up along the way, we evolved with them. So a study on the 5,300-year-old Iceman, found frozen in the Alps and kept in a museum ever since, pulled me straight in.
A conservation team wanted to work out which of his microbes are genuinely ancient, and which arrived later from three decades in the museum. One of the main ways they told the two apart was a kind of chemical clock, the way ancient DNA degrades over millennia.
A handful of his gut microbes were identified as ancient strains that matched what we see in non-Westernised guts today. A small window into what our guts may have looked like before ultra-processed food and antibiotics, and how far modern Western guts have drifted from it.
Then cold-loving yeasts on his skin that look alive, and may well still be growing. One of them went from 85% of the skinâs yeast community in 2010 to 98% by 2019, taking it over almost completely.
Some of these microbes even carry genes for breaking down collagen and the preservative once used to treat the body, which suggests the museumâs own conservation history may be feeding whatâs colonising his skin now.
So although heâs been dead for millennia, he isnât really a frozen relic. Freezing didnât stop life here, it just slowed it to a crawl.
Kiss and tell - do your partnerâs microbes affect yours?
With microbes all around us, on every surface and in the air, we know that we share microbes back and forth between the people we live with. What hasnât been looked at in the same way is how your mouth and your gut connect to that picture, given both have their own diverse microbiome.
You tend to share similar amounts of both gut and oral microbes with siblings, parents and children, but itâs with partners that the pattern breaks, and not in a way youâd expect.
It isnât that you share more microbes with a partner overall.
Itâs that, specifically, you share more in your mouth, about 44.4% of their oral strains, versus 19.5% of their gut strains, a gap that didnât show up for anyone else in the household. The mouth is the busier exchange site, and kissing is the obvious reason why.
One curious insight. Youâd assume the microbes that spread most easily between people would be the âgoodâ ones, the kind youâd want to pick up. Not so. The gut microbes transmitted most readily were actually the ones the researchers linked to worse cardiometabolic health, not better.
We canât say, for now, that your partnerâs gut is fixing or wrecking yours. This study simply mapped whoâs carrying what, not whose health changed because of it. But itâs interesting all the same.
Even when dementia's quietly brewing, diet still mattersâŠ
We know eating well is tied to a lower risk of cognitive decline, but whatâs been missing is whether it still matters once the earliest biological changes are already there, before a diagnosis.
A new study tracked three eating patterns, the Mediterranean diet, a general healthy-eating index, and an anti-inflammatory score, against blood markers of Alzheimerâs and broader brain ageing in adults over 60 followed for up to 15 years.
As expected, the Mediterranean diet and the healthy-eating index were tied to lower risk mainly in people whose biomarkers were still low. What was new though, is that the anti-inflammatory score stood out in the ones who already had elevated biomarkers, the early changes brewing before any symptoms.
My first reaction was wow, this is a promising early signal. My second, once I looked at how that score is built, was closer toâŠoh. That's because the anti-inflammatory score doesn't really translate into anything you can act on, as in, what do you actually put on your plate.
Strip out the strange bits and it's telling you to eat much like the other two do, more plants, less processed meat and sugary drinks. It's only where it breaks from them that it gets odd, and odd in the wrong direction. For example, it puts some fish and tomatoes on the inflammatory side, and wine and beer on the protective side. No, not a typo, and yes, you would expect the opposite.
But these foods were selected by a statistical tool, built by spotting which foods happened to track alongside higher inflammation in the blood of a group of American nurses in the late 1980s. Fish landing on the inflammatory side doesnât mean it harms you, it means it turned up next to inflammation in that data, maybe down to how it was cooked, maybe something else in those diets entirely.
So no shopping list from me on this one. What I do trust is the blunter point underneath, eating well still seemed to count even when the early changes were already there.
The fibre = bloating myth
If youâve stopped eating onions, garlic, or beans because youâre worried theyâll bloat you, this one may genuinely surprise you, and it did me.
Researchers recruited people who already got bloating and reckoned these fibres were a trigger for them, then fed them two types of highly fermentable fibre, fructans and GOS, the kind found in onions, garlic and beans. Fermentable means your gut microbes love feeding on them, and by feeding on them, they produce gas, which the theory goes can contribute to or cause bloating and discomfort.
This study was done properly. It was double-blind, so nobody knew which of the two fibres they were getting, and anyone who bloated on a dummy placebo had already been filtered out beforehand. Even then, only around one in five actually bloated. And remember, this is a group who already thought these fibres set them off, not the everyday person. On top of that, this was concentrated fibre powder at a set dose, not onions or beans on your plate where youâd get far less of it, so in real life the food itself is even less likely to be the problem.
So if youâve assumed fibre isnât for you, itâs likely worth actually testing that slowly, a little bit over time, rather than cutting it out âjust in caseâ. For some, there may still be issues, but it doesnât seem to be as common as itâs made out to be.
What predicted who reacted? Only small subtle signals from the gut microbiome, despite that being the obvious guess. The clearest predictor was more ordinary than that - the people who already had more gut symptoms and bloating to begin with were the ones who reacted.
The rest is for paid subscribers:
When you eat a meal changes how much you burn, and the best time for your biggest meal
The same cheese did two different things to peopleâs guts
How to eat more beans without the bloat
Plus a printable no-bloat beans guide to get you started
