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Follow Your Gut: The Enormous Impact of Tiny Microbes (TED Books) Hardcover – April 7, 2015
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“Deeply fascinating [and] altogether illuminating.” (Brain Pickings)
About the Author
Rob Knight is a Professor of Pediatrics and Computer Science & Engineering and Director of the Microbiome Initiative at the University of California, San Diego. He is cofounder of the American Gut Project and the Earth Microbiome Project.
Brendan Buhler is an award-winning science writer whose work has appeared in the Los Angeles Times, California, and Sierra Magazine. His story on Rob Knight’s work was selected for the 2012 edition of The Best American Science and Nature Writing.
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The book imparts a ton of information on an invisible, unknown world to most of us that has an enormous impact on our health and our mood: the microbiome. By reading this book, you get an immense appreciation for it. You also get a very different perspective on bacteria and microbes. The book creates an interesting tension between the germ theory and the hygiene theory.
The germ theory has dominated health care and medicine ever since Pasteur in the 1800s, whereby germs, bacteria, viruses are all bad and are powerful agents of diseases (often lethal and dreadful ones). Such illness-inducing agents should be wiped out at all costs through antibiotics. On the other hand, the hygiene theory advances that exposure to bacteria and microbes in the natural environment (farms, rural environments, nature, dirt, gardens) is actually really good for you. Interaction with many other groups of people and with pets is also good for you. It will render your own microbiome richer, more diverse, and will enhance your own health to be much more resilient than otherwise. It also warns against the excessive use of antibiotics for two reasons. The first one is that even when they are necessary they wipe out just as many good bacteria than bad ones. The second one is that the broad based use of antibiotics in soaps, other hygiene products, food for cattle has led to the antibioitic-resistance crisis.
After reading this book you will think twice about the germ theory vs hygiene theory tension. And, you will probably be on the hygiene theory side more often than you would have before reading the book.
The impact of the microbiome on just about everything is well documented within the book. The author in addition to his short and breezy narrative has included extensive notes and reference to the scientific literature. So, not only any of his arguments are very well supported; but, he readily facilitates you reading the scientific literature on the subject.
One of the most intriguing impact of the microbiome is on body weight (the obesity crisis). We give cattle a lot of antibiotics so they grow bigger and are more valuable in the marketplace. Strangely enough, there is a parallel in human beings. They uncovered that babies and toddlers that received more antibiotics than others as preventive measures to exposure to bad bacteria ended up with a lot higher probability of being overweight. They had also much higher rate of asthma, immune system disorders, and other ailments. The author had a really amazing first hand experience on the subject. On a trip to South America, he experienced a severe bout of gastro-intestinal problem (not unusual in that part of the World for American tourists with microbiome not diverse enough to withstand the local microbiome communities). To resolve his health issues he took a course of antibiotics. And, within just a few short months of coming back home he lost effortlessly 80 pounds! This triggered serious health concerns among his colleagues. They thought maybe he had cancer or something. It turns out he was perfectly healthy in all regards. However, his microbiome had profoundly changed after the trip as a result of his severe gastro-intestinal ailment and the antibiotics.
Microbiomics (if that is a word?) is a very young science faced with many conundrums. When you read the book you get a sense that the microbiome is very deterministic. In other words, a certain bacteria precisely has an impact on a certain disease or ailment; just like they have on weight and obesity. You also get that the microbiome of babies is radically different than the ones of adults, and the ones of women different than men. You also get that there are clear scientific categorical demarcations between good bacteria and bad ones. Also, throughout the book you get that diet is the most dominant causal driver of microbiome differentiation between individuals.
All of the above is most probably directionally correct. However, after reviewing some of the findings of the American Gut Project you realize the above statements are not so categorical. We are not talking of Yes/No or 100%/0% type binomial answers to anything. We are probably a lot closer to 51/49% type answers with a commensurate error margin leaving us with less than great confidence that anything is so Yes/No type situation. Let me give you a few examples.
When studying a large population of over 3,600 volunteers at the American Gut Project (AGP), they found that the recent use of antibioitics overall had very little impact on the overall microbiome composition of families of bacteria. In such, you could see a slight increase in Firmicutes and commensurate decrease in Proteobacteria when people first take their antibiotics. But, just a few weeks later their microbiome returns to some sort of original equilibrium (just a few percentage point different) and stay there.
Also, the influence of age is interesting and very nuanced. The microbiome mix of bacteria changes the most between babies and young children. During those few years, it does change quite a bit. Thereafter, strangely enough the microbiome mix gravitates very slowly towards the original mix at birth. So, by the time we reach our 80s our mix is fairly similar to what it was near birth (at least when observed over a large sample).
The influence of gender, appart from women having very different microbiome communities within their genital area than men, does not appear that pronounced. Women have typically a slightly more diverse overall microbiome than men. Does it contribute to women's longer lifespan in addition to obvious behavioral differences?
The influence of diet types when observed over a large sample is far less than one would think. Reading the related graph shown at the AGP, you really have to watch very closely for any visual difference between the microbiome mix of omnivores vs. vegetarians and even vegans.
The influence of exercise is actually a bit more noticeable than the influence of diets. The more people exercise the more Firmicutes they have.
Oddly enough, if we focus on Firmicutes… the more recently you have taken antibiotics the more Firmicutes you have. The more you exercise, the more Firmicutes you have. The more vegetarian/vegan diet you eat the moe Firmicutes you have. That’s even though the diet dimension, as mentioned before, is much harder to visually distinguish than the other ones.
So, what are those Firmicutes? In view of the above, you would think they have positive health implication. After consulting with Wikipedia this seems like a rather ambivalent proposition. Here is Wikipedia on the subject: “Firmicutes make up the largest portion of the mouse and human gut microbiome. The division Firmicutes as part of the gut flora has been shown to be involved in energy resorption and obesity.” From this take you would not necessarily derive that more Firmicutes is necessarily better.
So, what to do about all of this? At first early in the book, you get a sense that overall bacteria are so good for you that you should run straight to Whole Foods and load up on Probiotics. Not so fast, the author indicates that bacteria in a living form that would have any benefitial impact on your health are very fragile. It is unclear that such bacteria could survive the processing, packaging, transportation, and store shelving that facilitates your conveniently purchasing them at your local store. Additionally, if you take probiotics daily you may ingest about half a trillion good bacteria a year. That seems like a lot. But, your body has 100 trillion bacteria. This means over a year you would have ingested only 0.5% of the bacteria in your body. Also, the ones you ingest may be somehow half-dead for the mentioned reasons. How much are they likely to influence your overall microbiome over a year that is probably far more influenced by other behavioral and environmental factor over that same year. Given that, you may not need to spend much money on general probiotics if any.
Additionally, things are even more confusing than you think. They found that 30% of people that are perfectly healthy have bacteria that are dangerous pathogens. Why “bad” bacteria affect some people and not others is rather unclear. However, it seems that cultural genetic heritage can play a role. For instance, they uncovered that the biomarkers for several diseases are completely different for the Swedes vs. the Chinese. In other words, a bacteria that cause no problem in one population can be a dangerous pathogen in the other.
The above creates further uncertainty regarding what actionable steps you could take to enhance your microbiome.
There are a few simple steps you can take and that is to eat more yogurt, nuts and fiber rich foods (fruites and vegetables) that both enhance population of good bacteria. Pick up gardening, camping, hiking in nature, farming, get pets, and interact with people. Spend as much time outside instead of indoors. That’s all good.
Also, there seems to be one very specific bacteria recommendation. If you suffer from very severe and chronic gastro-intestinal problem (IBS, etc.) you may consider buying some VSL#3 probiotic. This is supported by an extensive number of scientific studies. Those are not your usual probiotics you buy at the store. They are a lot more specific, focused on seven types of bacteria that are very powerful in healing your gut. They are also offered in mega dose. Each dose contains a staggering 450 billion bacteria. That is up to nearly 500 more than your pain vanilla probiotic supplement at the store. They are also treated specially to be more "live" than otherwise. They are sent to you in a cool thermal or refrigerated package. And, you are supposed to refrigerate them immediately. Otherwise, they are obsolete after just two weeks. As you can imagine they are also a lot more expensive than your regular probiotics at the market. One dose of those probiotics can cost up to $3 dollars. While, regular probiotics are rather underpowered and immaterial relative to the scale of your own microbiome; one may wonder if those are at the opposite end. And, may be too much in certain circumstances. If you take one dose a day of VSL#3, you would ingest 164 trillions of bacteria a year? That is more than one and a half the amount of your entire microbiome. One would have to have pretty severe IBS or related disease before seriously considering such a remedy. So, it is not something you would casually take as a supplement just because you have a mild case of disturbance downstairs.