Sunday, December 10, 2017

Are nature and biodiversity essential to health and happiness?


There is no prize for guessing the answer given by Susan Prescott and Alan Logan in The Secret Life of your Microbiome: Why nature and biodiversity are essential to health and happiness.
This recently published book is written for a popular audience, but the authors have expert knowledge of the microbiome – the microbes and their genetic material found in the human gut and skin. Susan Prescott is an immunologist and paediatrician. Alan Logan’s background is in research relating to naturopathic medicine. It is obvious that the authors have spent a lot of time sifting through scientific evidence in writing the book.


Some of the evidence suggesting that nature and biodiversity are essential to health and happiness is derived from inspection of the stools of our Paleolithic ancestors. Evidence from archaeological sites suggests that our hunter and gatherer ancestors ate a wide variety of plant food and had a greater diversity of micro-biota than most people living modern lifestyles. The same is true today of people who are still living traditional lifestyles close to nature.

The authors accept that modern medicine and hygiene have brought great benefits, but they point to evidence that a diet with a great deal of sugar, ultra-processed food and drinks – as well as excessive use of antibiotics, stress and physical exhaustion – can lead to gut permeability, an increase in blood endotoxins, and an increase in central nervous system inflammatory chemicals. Intestinal permeability is apparently associated with a range of chronic conditions including autism, asthma, allergies, chronic fatigue, depression, fibromyalgia, heart disease, irritable bowel, obesity, type 2 diabetes, psoriasis and schizophrenia.

Prescott and Logan argue that we have a symbiotic relationship with the human microbiome, which co-evolved with our ancestors. The microbiome provides functional benefits such as nutrient extraction, protection against harmful microbes, regulation of metabolism and production of important biochemicals. Researchers don’t yet understand what microbes would comprise an ideal microbiome, but the key seems to be diversity, which is encouraged by dietary diversity. The authors suggest that the human immune system has evolved to expect a kaleidoscope of biodiversity.

The authors view commercially available probiotics and prebiotics as a useful supplement that can help defend against dysbiotic forces in the modern environment, rather than as a substitute for the adoption of a healthy lifestyle. They emphasize the importance of dietary choices, physical activity, sleep and experience of natural environments.

There is substantial evidence, some previously discussed on this blog, that experience of natural environments has a positive impact on health and happiness. Prescott and Logan provide an interesting account of Japanese research relating to shinrin-yoku – the absorption of the forest into the body and mind:

“Remarkable studies have demonstrated that, individually, the sounds of nature, the sights of nature, the invisible chemicals secreted from trees (phytoncides, or phytochemicals), and the touch of natural products like wood (compared to synthetic resin), can positively influence stress physiology and our parasympathetic nervous system, the “rest and digest” branch of the nervous system that cools the jets of over-stimulation. The sum of research shows that our sensory system understands nature like an old friend.”

One of the authors’ aims seems to be to promote nature relatedness – fascination with nature and a desire for contact with it. They note evidence that nature relatedness is associated with high levels of psychological wellbeing, lower anxiety and greater meaning and purpose in life. Experience in nature tends to lift nature relatedness scores. Practicing mindfulness while walking in nature has additional emotional benefits. Moreover, the combination of nature relatedness, mindfulness and meaningfulness of life promotes pro-environmental behaviours.

Prescott and Logan leave readers in no doubt that they view pro-environmental behaviours to be desirable. I agree with them.

However, I strongly disagree with authors about economics and politics. They argue:

“It’s up to governments, insulated against lobbyists, to help curb the wild west that is fueling the dysbiosphere. Time and time again industry has shown it just can’t stop itself from pushing dysbiotic choices on our children.

They oppose the view that “an individual can assume responsibility for personal health problems by simply adopting what biomedicine has to offer”. They suggest that view is deficient because it “doesn’t consider that a broken socio-ecological system might be the driving force for the need of biomedicine in the first place”.

When I read such views I have to remind myself that in writing about supporters of socialism Friedrich Hayek insisted “that it is neither selfish interests nor evil intentions but mostly honest convictions and good intentions which determine the intellectual's views”. (Quote from ‘The Intellectuals and Socialism’). It is not necessarily a waste of time to try to correct the errors of well-intentioned people.

Some of the errors made by Prescott and Logan are as follows:

1.       The view that government can be insulated against lobbyists is contrary to everything that is known about government and human nature.

2.       The phrase “pushing dysbiotic choices on our children” refers to advertising and selling products that are only harmful to human health when consumed inappropriately. There is nothing in our legal or economic system that requires parents to buy such products for their children or to allow them to over-indulge. Firms already offer foods for sale that are beneficial to health and will have a greater incentive to do so as consumers become more aware of the health implications of the choices they make on behalf of their children.

3.       The widespread human misery (and environmental catastrophes) caused by socialist economic experiments during the 20th century should make us wary of claims that the socio-ecological system is broken. In what respects is it broken? What precise interventions are proposed to fix it? And, are we sure, beyond reasonable doubt, that those interventions will produce better overall outcomes?

Susan Prescott and Alan Logan were unwise to include ill-informed rants on economics and politics in this book. It seems to me that those rants detract from their efforts to promote a revolution in attitudes toward the micro-biome and the environment.

In my view this book is nevertheless worth reading because of the substantial body of scientific evidence it provides that many aspects of human health and happiness depend on the microbiome.

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