Microbes by the Trillions

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Alanna Collen

I was given a dose of antibiotics long and intense enough to cure a herd of cattle. I learnt just how much I needed the 100 trillion friendly little creatures who had, until recently, called my body their home.

—Alanna Collen


Title: 10% Human: How Your Body’s Microbes Hold the Key to Health and Happiness
Author: Alanna Collen
Publisher: Harper Collins
Publication date: April 27, 2015
Price: $39.99; hardcover, 400 pages

"As I walked back through the forest that night in the summer of 2005, with twenty bats in cotton bags hanging around my neck and all manner of insect life dashing for the light of my torch, I realized my ankles were itching.” How can a reader resist a book with such an arresting opening? One can’t, and the good news is that it gets better all the way to the last page.

The book is called 10% Human: How Your Body’s Microbes Hold the Key to Health and Happiness and is ostensibly about the 100 trillion or so microbes that make up the other 90% of us. But it is much more than a book about microbes. It’s about us, the human beings they occupy for better or for worse.

The author, biologist Alanna Collen, draws on the latest scientific research to show how our personal colony of microbes influences our weight, our immune system, our mental health, and even the partner we choose. That’s a pretty big bite of ideas and information to chew and swallow, but this skilled author makes it work.

A Life-Changing Experience

The idea for 10% Human, in part, was planted by the author’s life-changing experience. During work for her biology degree, Ms. Collen became fascinated with bats and grabbed an opportunity to study bats in a Malaysian wildlife preserve. She was soon to learn that the trials of life in a tropical rain forest could live far beyond the experience itself.

She writes, “The humidity and drenching sweats, the muddy trails, my fear of tigers, and the mosquitos were enough to contend with as I made my rounds collecting bats. But something had got through the barrier of fabric and chemicals protecting my skin. Something itchy.”

Returning to base camp, Ms. Collen pealed back the layers of clothing to reveal 50 or so ticks that were embedded in her skin. She cocooned herself in a sleeping bag and by lamplight wrenched the ticks out with tweezers: one tough woman. Months later, back in London, the tropical infection introduced by the ticks took hold, bringing her to the brink of death. Weird symptoms came and went, her body would suddenly seize up, her feet would swell, and she had bouts of debilitating fatigue and pain.

When she was finally diagnosed years later, she writes, “I was given a dose of antibiotics long and intense enough to cure a herd of cattle.” The antibiotics cured Ms. Collen, but they also stripped her body not only of the bad bacteria, but also of those that belonged in her. “My skin was raw and I was prone to picking up every infection going. I felt I’d become inhospitable to microbes, and I learnt just how much I needed the 100 trillion friendly little creatures who had, until recently, called my body their home,” writes Ms. Collen.

Make no mistake, 10% Human is serious science writing and covers important public health issues. In fact, Ms. Collen argues quite persuasively that many of our modern diseases have their root in our failure to cherish our most fundamental and enduring relationship: that with our personal colony of microbes. Moreover, according to Ms. Collen, this relatively new line of inquiry elucidates many of the questions about modern diseases left unanswered by the Human Genome Project.

Satisfying on Every Level

A central challenge for science writers is to deal with heady scientific subjects in a way that is accessible and fun to read. People who read this kind of science book want to come away better informed and intellectually challenged by the content, but they don’t want to slog through run-on sentences full of scientific jargon.

Ms. Collen’s book satisfies on every level. And one reason is her devotion to the attention-grabbing opening, as evidenced by the start of chapter one, titled Twenty-First Century Sickness. “In September 1978, Janet Parker became the last person on Earth to die of smallpox.” Bang! She then treats the reader to a first-rate trip back in time, when there were “wards crammed full of sick and dying, wounds left open and rotting, and doctor’s coats covered in blood and gore after surgeries.”

After a fascinating history of the days when nasty microbes ran amok, the author discusses a theme that she threads throughout the book: the relationship of the gut and the immune system in the etiology of a variety of chronic diseases. She also makes a solid case for the rise of environmentally driven conditions such as asthma.

The ASCO Post readers may take issue with Ms. Collen’s downplaying the role of genetics in a host of autoimmune diseases, but she lays her therapies without sounding pedantic. Ms. Collen puts a lot of stock in what we put in our bodies and how we nurture or antagonize our microbes. She writes, “Despite all the hype, our human genome did not quite live up to our visions of becoming a blueprint for life and a philosophy for living…. For the first time, Darwin’s theory of evolution and our other 90 microbial percent are showing us the way to live.”

Moreover, she never stops at simply reporting the outcome of a given experiment or data set. For example, instead of jumping to the logical conclusion that higher worldwide fat and sugar consumption has led directly to the obesity crisis, she steps outside the box and asks whether the trouble is what we’re eating or what we’re not eating. If fat and sugar calories have displaced microbe-friendly foods like high-fiber vegetables, she notes, the body’s biome has likely also changed.

Ms. Collen’s book about microbes and public health issues moves around the globe, never lacking for interesting topics to highlight her theses. For example, in a chapter titled From the Very First Breath, she begins in Australia, where a koala joey is transitioning from feeding solely on mother’s milk to a diet of eucalyptus leaves.

The problem is that the mammalian genome is not equipped to produce enzymes necessary to produce anything of worth from eucalyptus leaves: Microbes and mother koala to the rescue. Via her saliva, the mother koala delivers a secretion of a predigested eucalyptus leaf to her offspring; once taken in his gut, the joey has its own army of microbes to make eucalyptus edible. This is one of her strongest chapters and the most science-heavy, dealing with oligosaccharides, live bacteria, hormones, and gut microbiota, all woven into a convincing argument for natural birthing practices and early health practices.

Ending Messages

The ending messages of the book at times run to preachy, a minor flaw in such an accomplished and well-written book. Ms. Collen speaks with the authority of a person who nearly died of an infection and then had her body re-altered into a walking infection magnet due to the massive doses of microbe-killing antibiotics needed to save her. This is a valuable book, because it deals with large-scale public health issues in a charmingly written format.

Ms. Collen leaves with an important message: “Antibiotics gave me back a quality of life I feared I’d lost, but along the way, they took me places I’d never experienced and I wouldn’t hesitate to take them if my life were in danger, but if I had the option to wait and see if my immune system might deal with it on its own, I would.”

10% Human is a page-turner that will leave science-loving readers wishing for more. It is strongly recommended for The ASCO Post reader. ■