I Contain Multitudes: The Microbes Within Us and a Grander View of Life

by Ed Yong

Even when we are alone, we are never alone. We exist in symbiosis

Walt Whitman: “I am large, I contain multitudes.”

there are more bacteria in your gut than there are stars in our galaxy.3

address how microbes affect our health, and which connections are, in his words, “causal not casual”.

gut bacteria:

obese people had more Firmicutes and fewer Bacteroidetes than their leaner counterparts.

fibre-busting specialists like B-theta.

Without fibre, the lean communities couldn’t establish themselves

A rainforest isn’t just a rainforest because of the birds, insects, monkeys, and plants within it, but also because ample rain and sunlight fall from above, and bountiful nutrients lurk in the soil.

A poor diet changes the microbes within.

impairs the child’s immune system, changing its ability to control the gut microbiome and opening the door to harmful infections that disrupt the communities even further.

Somewhere in the middle, always one tiny adjustment away, is the ideal setting, a point of perfect comfort.

immune system, for all its intricacy, is a lot like that dial. It works like an “immunostat”, which, rather than stabilising temperature, stabilises our relationships with our microbes.

over the last half-century, we have gradually pushed our immunostats to higher settings through a combination of sanitation, antibiotics, and modern diets.

We’ve ended up with immune systems that go berserk at harmless things like dust, molecules in our food, our resident microbes, and even our own cells.

inflammatory bowel disease, or IBD.

inflammation of the gut, which manifests as chronic pain, diarrhoea, weight loss, and fatigue.

IBD microbiome tends to be less diverse and less stable than its healthier counterparts.

anti-inflammatory microbes, including fibre-fermenters like Faecalibacterium prausnitzii and B. fragilis.

blooms of inflammatory species like Fusobacterium nucleatum and invasi...

These principles apply to other inflammatory diseases too, including type 1 diabetes, multiple sclerosis, allergies, asthma, rheumatoid arthritis and more.

common denominators is a simmering level of inflammation in the host.

major factors in our modern lifestyle that explain a large proportion of this.

there are five, or three, or maybe even one thing that explains 90 per cent of 90 per cent of these diseases. It

white population was more likely to get allergic diseases like asthma, eczema, and hives than the indigenous Metis communities,

“Hay fever, hygiene, and household size”. The middle ‘h’ was crucial. It eventually gave the idea its name: the hygiene hypothesis.

children in developed countries no longer run the gauntlet of infectious diseases that they used to, and so grow up with inexperienced, jumpy immune systems.

healthier in the short term, but they launch panicked immune responses to harmless triggers, like pollen.

various trappings of urbanisation: smaller families; a move from muddy countryside to concrete cities; a preference for chlorinated water and sanitised food; and a growing distance from livestock, pets and other animals.

higher risk of allergic and inflammatory diseases, and all of them reduce the range of microbes that we are exposed to.

This might explain why C-section babies are more likely to develop allergies, asthma, coeliac disease, and obesity later in life.

breast milk engineers a baby’s ecosystem. It provides more microbe colonists for a baby’s gut,

Saturated fats can nourish inflammatory microbes.

So can two common food additives, CMC and P80, used to lengthen the shelf life of ice cream, frozen desserts, and other processed foods; they also suppress anti-inflammatory bugs.25

Dietary fibre has the opposite effects. This is a catch-all term for various complex plant carbohydrates...

fibre-rich diet explained why Ugandans rarely suffer from diabetes, heart disease, colon cancer, and other diseases that are more common in the developed world.

Without fibre, we dial our immunostats to higher settings, predisposing us to inflammatory disease.

We not only eat fewer plants, we also heavily process the ones we do eat.

antibiotics are shock-and-awe weapons.

even short courses of antibiotics can change the human microbiome.

WEIRD countries – that is, Western, Educated, Industralised, Rich, and Democratic.

Scientists will talk about Occam’s razor – the principle that favours simple, elegant explanations over convoluted ones.

The Japanese have been eating nori for so long that their gut microbes are peppered with digestive genes from oceanic species.

Earth Microbiome Project – a breathtakingly ambitious plan to take full stock of the planet’s microbes.

Now is a time for thinking big.

All of these endeavours were propelled by curiosity, awe, and the exhilaration of exploration.