Self-Defense: A Myth-Busting Guide to Immune Health

by Daniel M. Davis

Overview

“Utterly absorbing. Nearly every paragraph brings a revelation.”—Bill Bryson • “Wise, and beautifully written. . . . It will change the way you think about your body and live your life.”—Chris van Tulleken • “This great book from a world expert offers practical tips and dispels many myths.”—Tim Spector

A world-renowned scientist offers a much-needed analysis of what it takes to have good immune health—helping readers navigate what can really help, what is a complete myth, and why.

Does orange juice help ward off colds? And how does our age affect our ability to recover from one? When it comes to immunity, are we really what we eat? Or how much we eat? We are surrounded by big questions and big claims about enhancing our immune systems, so how do we tell the fiction from the facts? And, ultimately, what can we do to reduce our chances of getting sick?
 
World-leading immunologist Daniel M. Davis offers answers in this authoritative, highly accessible, myth-busting guide to the effects of stress, age, exercise, weight, nutrition, sleep, vaccines, and mental health on our immune health. Taking us to the cutting edge of immunology research and explaining both what we know and how we know it, Self-Defense helps readers spot phony claims and make informed choices. Davis shows us that everyone’s immune system is entirely unique, and that’s why we should be wary of one-size-fits-all “cures.” We learn how exercise, for example, has all sorts of different, even opposing, short- and long-term effects on our immune health. And while our gut microbes are vitally important, it’s unlikely that yogurt drinks can really boost your immune system to stop you getting ill.
 
An eye-opening window into some of the astonishing possibilities for the future, when it comes to distinguishing bogus and beneficial health claims about everything from vitamin D to inflammation and cancer therapies, Davis’s book may be your best self-defense.

Product Details

ISBN-13:	9780226839387
Publisher:	University of Chicago Press
Publication date:	09/23/2025
Sold by:	Barnes & Noble
Format:	eBook
Pages:	256
File size:	797 KB

About the Author

Daniel M. Davis is head of life sciences and professor of immunology at Imperial College London. He is the author of The Compatibility Gene, The Secret Body, and The Beautiful Cure, the last also published by the University of Chicago Press and named a Book of the Year in the Times, Telegraph, and New Scientist. His writing has appeared in the United Kingdom’s leading newspapers, as well as in New Scientist, Wired, and Scientific American. In 2025, he was awarded an MBE in the King’s New Year's Honors list for services to science communication.

Table of Contents

Introduction: How we differ

1 Orange Juice and Sunshine – or, do vitamins help immune health?

2 The Aliens Living Inside You – or, does the microbiome affect immune health?

3 The Evidence of Weight – or, does weight affect immune health?

4 The Yin and Yang of Exercise – or, how much exercise is best?

5 A Reason for Calm – or, does stress impact immune health?

6 Inner Beauty Sleep – or, does sleep help immune health?

7 The Two Big Systems – or, does immune health affect mental health?

8 100-Year-Long Immunity – or, how does immune health change as we age?

9 In the Pipeline – or, what big new ideas are on the horizon?

Conclusion: the overarching journey

Acknowledgements

Glossary

Further Reading

Notes

Index

Editorial Reviews

“Davis conveys a visceral appreciation for how messy, and how human, medical science can be.”

— The Wall Street Journal, on "The Beautiful Cure"

“Refreshingly sober. . . . Intelligent and insightful.”

— The New York Review of Books, on "The Beautiful Cure"

"As David Attenborough opens our goggling eyes to the natural world without, so Davis brings us face to face with the stunningly clever and, yes, beautiful world within. . . . One of those books that makes you look at everything human in a new, challenging, and thrilling way."

— Stephen Fry, on "The Beautiful Cure"

"One of the best accounts I have yet come across of the nature of biological science and discovery."

— Henry Marsh, on "The Beautiful Cure"

"A brilliant deep-dive into the latest discoveries of human health. An inspiration!"

— Tim Spector, on "The Secret Body"

"A perfect blend of cutting-edge science and compelling storytelling. Davis has a rare knack for making complex science comprehensible and thrilling."

— Bill Bryson, on "The Secret Body"

“A beautifully written overview of the current state of the art in our understanding our immune system. But perhaps even more importantly, this book is an instruction manual which guides the reader through the blizzard of popular science and pseudoscience that inevitably obscures informed discussions about our health.”

— Brian Cox, world-renowned physicist, TV presenter, and author of Sunday Times–bestselling "Human Universe"

“This book is a masterclass in science communication. Davis unravels one of the most complex and vital elements of human biology, our immune system. Self-Defense disentangles the science of immunity and addresses some of the key questions we all want answered. Does orange juice really help us fight off colds, prevent us getting cancer, or combat HIV?  Do increased infections in early childhood protect against allergies, and is it true that children who grow up on farms are less likely to have asthma and hay fever? How might our genes or gut bacteria alter our vulnerability to infection? What is the link between obesity, stress, and sleep with our ability to fight infection? And does our immune system affect our mental health and the aging process? This is essential reading for anybody who wants to understand their health.”

— Russell Foster, neuroscientist and author of Sunday Times–bestselling “Life Time”

“Self-Defense: A Myth-Busting Guide to Immune Health uncovers how curiosity-driven science can help you truly understand and optimize your immune system—free from hype, misconceptions, and the traps of mistaking coincidence for causation. From the surprising links between cytokines and mood to the effects of stress on immunity, this book reveals how our biology shapes us in unexpected ways. With stories like how a glowing jellyfish transformed medical research, it shows how simple discoveries can lead to profound insights. Dive in to see how thoughtful, evidence-based exploration can lead to better health, resilience, and self-awareness.”

— Roger Highfield, science director at the Science Museum Group (London) and coauthor "The Dance of Life"

“A fascinating guide to the immune system, cutting through the myths with clear, evidence-based science. Davis empowers readers to make informed choices about their health in a world of so much misinformation.”

— Rhiannon Lambert, award-winning nutritionist (@rhitrition), co-host of The Wellness Scoop with Deliciously Ella, and Sunday Times–bestselling author of “The Science of Nutrition”

“The body is hugely complicated: you need a book, not a slogan, to unravel what helps keep it healthy. Fortunately, Davis has written an excellent guide to navigate you through the minefield of theories and speculations about what might boost our immune system. The answer is not easy, which is why you want an expert like Davis as your pilot through this difficult terrain.”

— Marcus du Sautoy, professor for the public understanding of science at University of Oxford, award-winning mathematician, and author of "Around the World in 80 Games" and “Blueprints”

"'Read this book! Your immune system is notoriously confusing yet vital and thus worth understanding. Fortunately, this succinct, clear, insightful, and fascinating book from one of the world’s experts on immunology will answer your most important questions about how best to help your body defend itself and stay healthy."

— Daniel Lieberman, professor at Harvard University and author of "Exercised"

"A brilliantly crafted immunization against the fads, fixes, and fraudsters that seek to improve our immune health. Davis draws on the past, present, and future of immunology to inform and explain what we can and importantly cannot do."

— John Tregoning, professor at Imperial College London and author of "Live Forever"

"A thought-provoking, insightful guide to the immune system's vital role in protecting our bodies and minds. With clarity and precision, Davis explores how we can harness this incredible system to stay well in our ever-evolving world. A must-read for anyone looking to empower themselves with the science of staying well."

— Dr. Jenna Macciochi, immunologist and author of "Immunity"

"The immune system holds the key to modern diseases—everyone should know more about it—and this great book from a world expert offers practical tips and dispels many myths on how best to enhance it."

— Tim Spector, author of "The Diet Myth," "Spoon-Fed," and "Food for Life" and co-founder of ZOE

"Admirably clear, readable, and reliable. Davis writes with infectious enthusiasm about the beauty and complexity of human immunity."

— Dr. Gavin Francis, author of "Recovery: The Lost Art of Convalescence"

"An engaging and thorough look at the factors affecting our immune health. If you've ever been tempted to take steps to 'boost your immunity,' read this first!"

— Sarah Gilbert, professor of vaccinology at the University of Oxford and coauthor of "Vaxxers: The Inside Story of the Oxford AstraZeneca Vaccine and the Race Against the Virus"

"Utterly absorbing. Nearly every paragraph brings a revelation."

— Bill Bryson, author of "The Body"

"The ultimate self-help book—genuinely one of the most worthwhile books I've ever read. Davis is a captivating and authoritative guide, addressing many seemingly simple questions about our immune health, from vitamins to vaccines, from stress to the microbiome. We learn how to learn about the only thing in the universe that’s arguably more complex than the human brain."

— Nick Lane, author of "Transformer"

"There is so much misinformation in the health and science arena that it can be really challenging to pick the truth out of all that fiction. Self-Defense is a perfect antidote to so many of those assumed truths about immune health that have gone unchallenged for way too long. It is a refreshing, expert examination of health myths, beautifully written, packed with science but always accessible. I learned a lot."

— Suzanne O’Sullivan, author of "The Age of Diagnosis"

"We all retain some traditional beliefs about what lifestyles and everyday remedies are good for us; this clearly written book by a distinguished expert tells us which ideas are grounded in science, and which are not. An enjoyable read with messages that can improve our health."

— Martin Rees, author of "If Science Is to Save Us"

"Why does weight-loss drug Ozempic reduce dementia risk, and what’s the connection between the bacteria living in your gut and risk of allergies? The answer—as in so many parts of biology—is the immune system. Self-Defense takes us on a fascinating tour of our bodies, linking happenings inside our cells to everyday practical advice, and dealing with pervasive myths about vitamins, inflammation, and more along the way. This book will do more for your health than any bottle of vitamin C tablets!"

— Andrew Steele, author of "Ageless"

"A masterful exploration of what we know (and don’t know) about the workings of this most crucial of bodily functions. In a world of sales patter, soundbites, and social media videos, scientific rigor, clarity, and nuance is much needed. Self-Defense provides precisely that. Davis dissects claims and widely held beliefs surrounding the workings of our immune system, and shines a light on what is myth, hype, uncertainty, and scientific truth."

— Guy Leschziner, author of "Seven Deadly Sins"

"Davis is a world-class scientist and one of the best science communicators of his generation. From the role of tobacco scientists in promoting stress to why astronauts take antihistamines, Self-Defense will answer every question you have about your immune system and many more. It is deeply absorbing, wise, and beautifully written. Packed with astounding science, compelling stories, and ideas, it will change the way you think about your body and live your life."

— Chris van Tulleken, author of "Ultra-Processed People"

"Expertly cutting through all the myths, marketing hype, and simple slogans, this is the best book on immune health I have ever read."

— Alice Roberts, author of "Crypt"

"A clear-eyed, myth-busting manual to managing immune health. I learned a lot about what I was doing wrong for so long—and how to set it right."

— James Nestor, author of "Breath"

"This is the clearest, most authoritative, and most honest guide I have seen to the kinds of questions about our health and our immunity that we encounter all the time. What is the best diet? Does exercise help? What does our microbiome really do? Is good sleep so important? With patience, humility, humanity, and generosity, Davis provides a primer on immunity that should be on everyone’s bookshelf."

— Philip Ball, author of "How Life Works"

"Wellness gets the expert treatment as Davis filters out the bullshit/hype and hearsay in a clarifying sweep to reveal the fascinating complexity around how our body maintains health, and how we can help it."

— Gaia Vince, author of "Nomad Century"

"In Self-Defense, immunologist Davis explains everything that we know about our immune systems with clear, concise, and engaging stories based in the latest science, not hype. So, if you're tired of all the people trying to sell you things that they swear will improve your immune function, but then never do, this book is for you. Davis walks us through the often complicated answers to all our questions and shows us that there is no such thing as a one-size-fits-all solution to immune health."

— Theresa MacPhail, author of "Allergic"

"After giving public lectures, the immunologist Davis usually finds himself being asked a 'series of seemingly simple but actually really difficult questions, mostly, if not exclusively, about how to achieve good immune health.' He is, of course, under pressure to provide snappy answers to his audience’s enquiries: does orange juice ward off colds? Should we take vitamin D? How can I boost my immune system? Self-Defense is his longer, more considered answer to these questions, and it aims to bridge the gap between the scientific research of his day job and what people want to know about immunity. . . . Self-Defense is a reminder that there's a lot of research behind even our simplest questions about the immune system. Davis follows the twists and turns of the evidence and offers nuanced responses to immune health questions. . . . Above all, his friendly tone and clear writing give the reader a much deeper appreciation of the complexity of the human body."

— Times Literary Supplement

"With the recent publication of his fourth book, Self Defense, Dan’s work shines a light on how immunology can influence our health, demystify the science behind many diet and lifestyle claims, and helps his audiences understand just how complex our biological systems really are."

— British Society for Immunology

"Davis frames the human immune system as a linchpin of our health, serving as both the cure and cause—in disorders of autoimmunity—of many diseases. The book treads familiar questions with exceptional sharpness. Do vitamins work? What is the role of the microbiome? What is the impact of weight, exercise, stress, and sleep on human health? How does our immune system change as we age? Each of the book’s chapters is prefaced with a widely held health myth or preconception. Davis then explores the relevant immunological pathways, diving into the research, confounding variables, and methodological biases that underlie it. . . . The book succeeds in inoculating the reader against easy health answers, headlines, and platitudes. When it comes to our immune system, as Davis writes, 'there’s always more to the story.'"

— Science

From the Publisher