James Kinross (Penguin Life)
IT HAS been 30 years since my appendix and I parted company. As I lay debilitated and miserable in hospital, I told myself the surgeon hadn’t removed anything vital, just a functionless relic. And an antibiotic drip was cleansing me of my foes, bacteria – after all, they had inflamed my appendix. Such thoughts stopped me feeling sorry for myself, but as James Kinross relates in Dark Matter: The new science of the microbiome, we now know how wrong they were.
Kinross is a colorectal surgeon at St Mary’s Hospital in London and an expert on the human microbiome, the dizzyingly complex ecosystem of microbes that live on and in our bodies. Like most clinicians, he saw them as the enemy. But the rise of non-communicable conditions, such as allergies, autoimmune diseases and obesity, and their links with changes to the microbiome has led many to seek a more sophisticated view of our relationship with the microbial world. The book is the story of Kinross’s conversion to this new view and a call to action.
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He sets out his thesis in three parts, starting with the analogy he draws between the mysterious cosmological dark matter and the microbiome. The latter appears to have a large influence on our health, though one not accounted for in the “standard model” of medicine, and we still know relatively little about it.
Together with our human bodies, goes the new view, microbial ecosystems form the human “holobiont”, seeded at birth and moulded by our environment and our immune system. This neatly reframes the role of the immune system from one focused solely on defence to one that cooperates with the microbiome to shape our immune responses. The appendix, for example, is now seen as an important immunological organ that acts as a reserve of gut microbes. When this cooperative arrangement falls apart, the result can be allergies and other immunological problems.
Next, Kinross turns to the “exposome”, describing how we and the environment affect the microbiome. This makes sobering reading as he explains the impact of overusing antibiotics and the loss of biodiversity in the gut microbiomes of people in industrialised countries. Diet is a key factor, but so are wider changes, including microplastics in the environment and the effects of climate change. He also points to how the microbiome affects the action of medicines and, in turn, how they alter the microbiome. Doctors aren’t just treating the patient when they prescribe drugs.
In the final section, Kinross writes about how the exposome has changed our microbiomes over generations. Fixing this will be a tall order: a future in which we can manipulate our gut microbiomes with microbial transplants (natural or synthetic) is exciting, but distant. Meanwhile, we must guard what we have. “Our guts are an ecosystem worthy of protection – exactly like a rainforest,” writes Kinross. “We can only improve things if we take collective responsibility.”
This isn’t the first popular science book about the human microbiome, but Kinross’s approach is engaging, and there are always new things to say in a fast-moving field. For me, though, his book really stands out in revealing the microbiome through the eyes of a clinician who sees each patient not just as a human, but as a human entwined with a complex, dynamic ecosystem. It envisions a future where a doctor-patient relationship is more like that of ecologist and holobiont, where we no longer tilt indiscriminately at microbes, but prize biodiversity in our bodies and the wider world.
Claire Ainsworth is a science writer based in Hampshire, UK
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