‘We’re identical twins but our gut microbes were completely different’

Identical twins Lisa Macfarlane and her sister Alana’s lives could not be more intertwined. As children they shared the same home, influences and diet. As young adults they rented a flat and forged DJ careers together.

“We’re 100 per cent genetically identical,” says Lisa, 33.  However, there was one way in which the twins were to differ greatly. 

In 2015, they signed up to a study to have their microbiomes analysed - being among the first people in the UK to do so. The results? “Our gut bacteria turned out to be only 30 per cent the same,” says Lisa. “The same as strangers.”

“As a twin, you grow up thinking everything about you is exactly the same,” says Alana. “So at first, we were just delighted to find out there was something different about us.” Soon, however, they began to ask questions. If their genetics and environments matched, might this one variant be responsible for their very different health experiences?

Your microbiome is made up of over a trillion microbes – bacteria, viruses, fungi and other organisms – many of which make homes in our large intestine, outnumbering human cells, and influencing our lives to a degree we are only beginning to fathom.

“We’ll never know exactly why our microbiomes were so different, but they think it could have been caused by a course of antibiotics that I was on when we were three or four,” says Alana. From then on, their paths diverged: “Alana had really debilitating, chronic juvenile arthritis and I didn’t,” says Lisa. “I had really bad acne and she didn’t.”

That 2015 test proved a turning point for the sisters: “We met gastroenterologists, immunologists and more, and realised that gut bacteria is responsible for so much more than just the digestion of food,” says Lisa. “We just could not believe how many health issues it was linked to. We thought: how can we shout this from the roof tops?”

The answer is Know Your Sh!t, a six-part Channel 4 show starting on Tuesday, in which members of the public visit the twins’ ‘Poo HQ’ – a clinic where an expert dietician, gastroenterologist and other medical professionals get to, well, the bottom of their digestive problems.

They may come with concerns about their bowels, says Lisa, but “what surprises people is that as soon as the experts start to dig deeper, they unearth potential links to other things that have been going on with their health, both physical and mental.”

Mental health

“Mental health is so multifactorial, so gut health has to be one tool among others in your armoury,” says Lisa. But, as the show points out, 90 per cent of serotonin – a chemical that helps regulate your mood - is produced in your gut. Moreover,  a 2019 analysis from Belgium’s Flemish Gut Flora Project found that two groups of bacteria, Coprococcus and Dialister, were diminished among people with depression. 

Though the study identified correlation, not cause, an editorial in the journal Nature called its results: “some of the strongest yet to show that a person’s microbiota can influence their mental health”.

Skin 

“The links between gut health and the skin are amazing, too,” says Lisa. Recent studies have identified links between the most common form of eczema - atopic dermatitis - and gut health, with some suggesting that sufferers have a reduced range of gut bugs. “If I was still suffering from acne today, my microbiome would be my first port of call,” says Lisa.

Autoimmune diseases

“The links between gut health and conditions like rheumatoid arthritis – the condition I suffered from when I was young – are becoming clearer and clearer too,” says Alana. In fact, studies have linked the gut microbiome to autoimmune conditions from lupus to type one diabetes via multiple sclerosis.

Heart

Your gut microbes have even been linked to your heart health, with one 2012 study identifying differences between the microbiomes of people with atherosclerosis (clogged arteries) and those without. While there’s no proof yet that this link is causal, it’s one that strikes the twins particularly powerfully. 

“Our dad died of a heart attack in his 50s,” says Lisa. “So many people think you’re born with this genetic imprint and that’s what will happen to you. For us, it was really empowering to think, not only is it within our control, but it’s cheap and simple to modulate your microbiome.”

How to help your microbiome flourish 

“A lot of it is what our grannies told us,” says Alana. “Drink more water, eat a wide range of plant foods (ideally 30 plus different ones a week). Ninety per cent of Brits aren’t getting the 30 grams of fibre a day that our microbes need. And move around! Studies show that when people who live sedentary lifestyles exercise, the diversity of their microbiome goes up.”

All of which begs the question: what changes have the twins noticed in their own health since they began to implement this advice? Their microbiomes were re-analysed for the show and: “I think everyone will be very surprised at the level we’ve managed to crawl ourselves up to,” says Lisa.

“Sleep is the main thing that’s changed for me, I used to have really bad insomnia,” says Lisa. “Now I go to bed at 9pm and I sleep pretty much straight through.”

“My energy levels are a lot higher, I got ill a lot less,” says Alana. And her arthritis? “It’s definitely not debilitating like it was. I do think working on my microbiome has been a really big part of that. I used to really suffer but in 2018 we ran a marathon. For me that was just amazing.”