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Thursday, January 07, 2021

Review: Clean

 Clean was on the Smithsonian 20 best science books of the year, and it was written by a doctor who's a staff writer at The Atlantic, so I checked it out of the library. The book begins strongly, with the doctor proclaiming that he hadn't showered for years. Then he gets into the reason behind it, including a fun reading history of soap, as well as the sad lack of regulation behind personal care products:

European Union and Canada have been reviewing ingredients in personal care products for decades. More than 1,500 chemicals are banned or restricted from these products in the European Union, and some 800 are banned or restricted in Canada. California state lawmakers proposed a bill in 2019 that would ban the inclusion of lead, formaldehyde, mercury, asbestos, and many other potentially harmful compounds from personal care products, which, if enacted, would be the first legislation of its kind in the United States. As of this writing, the effort has not yet been successful. (kindle loc 1505)

But the detail isn't there. There's no discussion as to whether not showering or bathing will solve eczema, a common childhood ailment. No studies (double-blinded or not), just loads and loads of anecdotal evidence. We get lots of copy text about how little regulation there is for makeup and other health supplements (which you would know about if you'd even read one other non-fiction book about the topic), but the scientific evidence is sadly lacking. There is a note that Dove is a particularly ineffective soap, which is why it gets to be marketed as mild!

The book then branches out into various other aspects of the hygiene hypothesis and the rise of allergy and asthma:

 In wealthy countries around the world, people now spend more than 90 percent of their lives indoors. Friends and family are not allowed to touch babies unless their hands have been scrubbed or coated in antibacterial gels. The indoor air is lacking in the wealth of bacterial particles that used to temper our immune systems. Our diet is hyperprocessed and cleaned and low in fresh fruits and vegetables—which are naturally loaded with bacteria. An average apple contains 100 million microbes. (kindle loc 1765)

But there's no real detail behind it. There's nothing about whether eating apple skin is good for you, no studies, and definitely no clinical recommendations. The entire book goes on like this, with forays into green space exposure and outdoor exercise vs indoor exercise: 

A number of studies have reported associations between green-space exposure and self-reported health, birth outcomes, and reduced morbidity. A 2018 meta-analysis found statistically significant associations between exposure to green spaces and reduced blood pressure, heart rate, cortisol levels, incidence of type 2 diabetes, and death from cardiovascular disease. Exercising outdoors may also have health benefits you don’t get at the gym. Much work has been done in this area by Diana Bowler and colleagues in the UK, who compared the effects of exercise in “natural” and “synthetic” environments and found that a walk or run outside “may convey greater health benefits than the same activity in a synthetic environment.” (kindle loc 2004)

At least this particular instance had great relevance to me and some literature citations, but the author provides no quantification of the results, and clearly the science here is difficult to do (how do you do a double-blind study of a topic like this one?). I came away with the book vaguely dissatisfied. I cannot sincerely recommend this book.

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